diff --git a/libc/src/stdio/CMakeLists.txt b/libc/src/stdio/CMakeLists.txt
index b0a6ef1e291b5..7f8c95ef7b41e 100644
--- a/libc/src/stdio/CMakeLists.txt
+++ b/libc/src/stdio/CMakeLists.txt
@@ -125,6 +125,9 @@ add_entrypoint_object(
   DEPENDS
     libc.src.stdio.printf_core.printf_main
     libc.src.stdio.printf_core.writer
+    libc.src.stdio.printf_core.core_structs
+    libc.src.stdio.printf_core.error_converter
+    libc.src.__support.libc_errno
 )
 
 add_entrypoint_object(
@@ -136,6 +139,9 @@ add_entrypoint_object(
   DEPENDS
     libc.src.stdio.printf_core.printf_main
     libc.src.stdio.printf_core.writer
+    libc.src.stdio.printf_core.core_structs
+    libc.src.stdio.printf_core.error_converter
+    libc.src.__support.libc_errno
 )
 
 add_entrypoint_object(
@@ -146,6 +152,9 @@ add_entrypoint_object(
     asprintf.h
   DEPENDS
     libc.src.stdio.printf_core.vasprintf_internal
+    libc.src.stdio.printf_core.core_structs
+    libc.src.stdio.printf_core.error_converter
+    libc.src.__support.libc_errno
 )
 
 add_entrypoint_object(
@@ -157,6 +166,8 @@ add_entrypoint_object(
   DEPENDS
     libc.src.stdio.printf_core.printf_main
     libc.src.stdio.printf_core.writer
+    libc.src.stdio.printf_core.core_structs
+    libc.src.stdio.printf_core.error_converter
 )
 
 add_entrypoint_object(
@@ -168,6 +179,9 @@ add_entrypoint_object(
   DEPENDS
     libc.src.stdio.printf_core.printf_main
     libc.src.stdio.printf_core.writer
+    libc.src.stdio.printf_core.core_structs
+    libc.src.stdio.printf_core.error_converter
+    libc.src.__support.libc_errno
 )
 
 add_entrypoint_object(
@@ -178,6 +192,9 @@ add_entrypoint_object(
     vasprintf.h
   DEPENDS
     libc.src.stdio.printf_core.vasprintf_internal
+    libc.src.stdio.printf_core.core_structs
+    libc.src.stdio.printf_core.error_converter
+    libc.src.__support.libc_errno
 )
 
 add_subdirectory(printf_core)
diff --git a/libc/src/stdio/asprintf.cpp b/libc/src/stdio/asprintf.cpp
index f8cfb74ce48ea..49183c0614abc 100644
--- a/libc/src/stdio/asprintf.cpp
+++ b/libc/src/stdio/asprintf.cpp
@@ -8,7 +8,10 @@
 
 #include "src/stdio/asprintf.h"
 #include "src/__support/arg_list.h"
+#include "src/__support/libc_errno.h"
 #include "src/__support/macros/config.h"
+#include "src/stdio/printf_core/core_structs.h"
+#include "src/stdio/printf_core/error_converter.h"
 #include "src/stdio/printf_core/vasprintf_internal.h"
 
 namespace LIBC_NAMESPACE_DECL {
@@ -22,8 +25,18 @@ LLVM_LIBC_FUNCTION(int, asprintf,
                                  // and pointer semantics, as well as handling
                                  // destruction automatically.
   va_end(vlist);
-  int ret = printf_core::vasprintf_internal(buffer, format, args);
-  return ret;
+  auto ret_val = printf_core::vasprintf_internal(buffer, format, args);
+  if (!ret_val.has_value()) {
+    libc_errno = printf_core::internal_error_to_errno(ret_val.error());
+    return -1;
+  }
+  if (ret_val.value() > cpp::numeric_limits<int>::max()) {
+    libc_errno =
+        printf_core::internal_error_to_errno(-printf_core::OVERFLOW_ERROR);
+    return -1;
+  }
+
+  return static_cast<int>(ret_val.value());
 }
 
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/baremetal/CMakeLists.txt b/libc/src/stdio/baremetal/CMakeLists.txt
index 548938f885c94..3f97254356001 100644
--- a/libc/src/stdio/baremetal/CMakeLists.txt
+++ b/libc/src/stdio/baremetal/CMakeLists.txt
@@ -29,8 +29,11 @@ add_entrypoint_object(
   DEPENDS
     libc.src.stdio.printf_core.printf_main
     libc.src.stdio.printf_core.writer
+    libc.src.stdio.printf_core.error_converter
+    libc.src.stdio.printf_core.core_structs
     libc.src.__support.arg_list
     libc.src.__support.OSUtil.osutil
+    libc.src.__support.libc_errno
 )
 
 add_entrypoint_object(
@@ -87,8 +90,11 @@ add_entrypoint_object(
   DEPENDS
     libc.src.stdio.printf_core.printf_main
     libc.src.stdio.printf_core.writer
+    libc.src.stdio.printf_core.error_converter
+    libc.src.stdio.printf_core.core_structs
     libc.src.__support.arg_list
     libc.src.__support.OSUtil.osutil
+    libc.src.__support.libc_errno
 )
 
 add_entrypoint_object(
diff --git a/libc/src/stdio/baremetal/printf.cpp b/libc/src/stdio/baremetal/printf.cpp
index 7253c6549a4e4..74748a85ce614 100644
--- a/libc/src/stdio/baremetal/printf.cpp
+++ b/libc/src/stdio/baremetal/printf.cpp
@@ -9,8 +9,10 @@
 #include "src/stdio/printf.h"
 #include "src/__support/OSUtil/io.h"
 #include "src/__support/arg_list.h"
+#include "src/__support/libc_errno.h"
 #include "src/__support/macros/config.h"
 #include "src/stdio/printf_core/core_structs.h"
+#include "src/stdio/printf_core/error_converter.h"
 #include "src/stdio/printf_core/printf_main.h"
 #include "src/stdio/printf_core/writer.h"
 
@@ -42,13 +44,25 @@ LLVM_LIBC_FUNCTION(int, printf, (const char *__restrict format, ...)) {
       buffer, BUFF_SIZE, &stdout_write_hook, nullptr);
   printf_core::Writer<printf_core::WriteMode::FLUSH_TO_STREAM> writer(wb);
 
-  int retval = printf_core::printf_main(&writer, format, args);
+  auto retval = printf_core::printf_main(&writer, format, args);
+  if (!retval.has_value()) {
+    libc_errno = printf_core::internal_error_to_errno(retval.error());
+    return -1;
+  }
 
   int flushval = wb.overflow_write("");
-  if (flushval != printf_core::WRITE_OK)
-    retval = flushval;
+  if (flushval != printf_core::WRITE_OK) {
+    libc_errno = printf_core::internal_error_to_errno(-flushval);
+    return -1;
+  }
 
-  return retval;
+  if (retval.value() > cpp::numeric_limits<int>::max()) {
+    libc_errno =
+        printf_core::internal_error_to_errno(-printf_core::OVERFLOW_ERROR);
+    return -1;
+  }
+
+  return static_cast<int>(retval.value());
 }
 
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/baremetal/vprintf.cpp b/libc/src/stdio/baremetal/vprintf.cpp
index ab02533f14911..8170a3b16f22e 100644
--- a/libc/src/stdio/baremetal/vprintf.cpp
+++ b/libc/src/stdio/baremetal/vprintf.cpp
@@ -9,8 +9,10 @@
 #include "src/stdio/vprintf.h"
 #include "src/__support/OSUtil/io.h"
 #include "src/__support/arg_list.h"
+#include "src/__support/libc_errno.h"
 #include "src/__support/macros/config.h"
 #include "src/stdio/printf_core/core_structs.h"
+#include "src/stdio/printf_core/error_converter.h"
 #include "src/stdio/printf_core/printf_main.h"
 #include "src/stdio/printf_core/writer.h"
 
@@ -40,13 +42,25 @@ LLVM_LIBC_FUNCTION(int, vprintf,
       buffer, BUFF_SIZE, &stdout_write_hook, nullptr);
   printf_core::Writer<printf_core::WriteMode::FLUSH_TO_STREAM> writer(wb);
 
-  int retval = printf_core::printf_main(&writer, format, args);
+  auto retval = printf_core::printf_main(&writer, format, args);
+  if (!retval.has_value()) {
+    libc_errno = printf_core::internal_error_to_errno(retval.error());
+    return -1;
+  }
 
   int flushval = wb.overflow_write("");
-  if (flushval != printf_core::WRITE_OK)
-    retval = flushval;
+  if (flushval != printf_core::WRITE_OK) {
+    libc_errno = printf_core::internal_error_to_errno(-flushval);
+    return -1;
+  }
 
-  return retval;
+  if (retval.value() > cpp::numeric_limits<int>::max()) {
+    libc_errno =
+        printf_core::internal_error_to_errno(-printf_core::OVERFLOW_ERROR);
+    return -1;
+  }
+
+  return static_cast<int>(retval.value());
 }
 
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/generic/CMakeLists.txt b/libc/src/stdio/generic/CMakeLists.txt
index 6361822b61999..34ab478777e5e 100644
--- a/libc/src/stdio/generic/CMakeLists.txt
+++ b/libc/src/stdio/generic/CMakeLists.txt
@@ -394,6 +394,8 @@ list(APPEND fprintf_deps
       libc.hdr.types.FILE
       libc.src.__support.arg_list
       libc.src.stdio.printf_core.vfprintf_internal
+      libc.src.stdio.printf_core.core_structs
+      libc.src.stdio.printf_core.error_converter
 )
 
 if(LLVM_LIBC_FULL_BUILD)
diff --git a/libc/src/stdio/generic/fprintf.cpp b/libc/src/stdio/generic/fprintf.cpp
index 087aeadfc52c5..6126a00665a9f 100644
--- a/libc/src/stdio/generic/fprintf.cpp
+++ b/libc/src/stdio/generic/fprintf.cpp
@@ -11,6 +11,8 @@
 #include "src/__support/File/file.h"
 #include "src/__support/arg_list.h"
 #include "src/__support/macros/config.h"
+#include "src/stdio/printf_core/core_structs.h"
+#include "src/stdio/printf_core/error_converter.h"
 #include "src/stdio/printf_core/vfprintf_internal.h"
 
 #include "hdr/types/FILE.h"
@@ -27,8 +29,18 @@ LLVM_LIBC_FUNCTION(int, fprintf,
                                  // and pointer semantics, as well as handling
                                  // destruction automatically.
   va_end(vlist);
-  int ret_val = printf_core::vfprintf_internal(stream, format, args);
-  return ret_val;
+  auto ret_val = printf_core::vfprintf_internal(stream, format, args);
+  if (!ret_val.has_value()) {
+    libc_errno = printf_core::internal_error_to_errno(ret_val.error());
+    return -1;
+  }
+  if (ret_val.value() > cpp::numeric_limits<int>::max()) {
+    libc_errno =
+        printf_core::internal_error_to_errno(-printf_core::OVERFLOW_ERROR);
+    return -1;
+  }
+
+  return static_cast<int>(ret_val.value());
 }
 
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/generic/printf.cpp b/libc/src/stdio/generic/printf.cpp
index bb7c7c86f843f..2a40f59011a40 100644
--- a/libc/src/stdio/generic/printf.cpp
+++ b/libc/src/stdio/generic/printf.cpp
@@ -11,6 +11,8 @@
 #include "src/__support/File/file.h"
 #include "src/__support/arg_list.h"
 #include "src/__support/macros/config.h"
+#include "src/stdio/printf_core/core_structs.h"
+#include "src/stdio/printf_core/error_converter.h"
 #include "src/stdio/printf_core/vfprintf_internal.h"
 
 #include "hdr/types/FILE.h"
@@ -31,9 +33,19 @@ LLVM_LIBC_FUNCTION(int, printf, (const char *__restrict format, ...)) {
                                  // and pointer semantics, as well as handling
                                  // destruction automatically.
   va_end(vlist);
-  int ret_val = printf_core::vfprintf_internal(
+  auto ret_val = printf_core::vfprintf_internal(
       reinterpret_cast<::FILE *>(PRINTF_STDOUT), format, args);
-  return ret_val;
+  if (!ret_val.has_value()) {
+    libc_errno = printf_core::internal_error_to_errno(ret_val.error());
+    return -1;
+  }
+  if (ret_val.value() > cpp::numeric_limits<int>::max()) {
+    libc_errno =
+        printf_core::internal_error_to_errno(-printf_core::OVERFLOW_ERROR);
+    return -1;
+  }
+
+  return static_cast<int>(ret_val.value());
 }
 
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/generic/vfprintf.cpp b/libc/src/stdio/generic/vfprintf.cpp
index 01f4265f118a6..a00a66d993962 100644
--- a/libc/src/stdio/generic/vfprintf.cpp
+++ b/libc/src/stdio/generic/vfprintf.cpp
@@ -11,6 +11,8 @@
 #include "src/__support/File/file.h"
 #include "src/__support/arg_list.h"
 #include "src/__support/macros/config.h"
+#include "src/stdio/printf_core/core_structs.h"
+#include "src/stdio/printf_core/error_converter.h"
 #include "src/stdio/printf_core/vfprintf_internal.h"
 
 #include "hdr/types/FILE.h"
@@ -24,8 +26,18 @@ LLVM_LIBC_FUNCTION(int, vfprintf,
   internal::ArgList args(vlist); // This holder class allows for easier copying
                                  // and pointer semantics, as well as handling
                                  // destruction automatically.
-  int ret_val = printf_core::vfprintf_internal(stream, format, args);
-  return ret_val;
+  auto ret_val = printf_core::vfprintf_internal(stream, format, args);
+  if (!ret_val.has_value()) {
+    libc_errno = printf_core::internal_error_to_errno(ret_val.error());
+    return -1;
+  }
+  if (ret_val.value() > cpp::numeric_limits<int>::max()) {
+    libc_errno =
+        printf_core::internal_error_to_errno(-printf_core::OVERFLOW_ERROR);
+    return -1;
+  }
+
+  return static_cast<int>(ret_val.value());
 }
 
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/generic/vprintf.cpp b/libc/src/stdio/generic/vprintf.cpp
index 08d71515646ed..829cf232834e2 100644
--- a/libc/src/stdio/generic/vprintf.cpp
+++ b/libc/src/stdio/generic/vprintf.cpp
@@ -11,6 +11,8 @@
 #include "src/__support/File/file.h"
 #include "src/__support/arg_list.h"
 #include "src/__support/macros/config.h"
+#include "src/stdio/printf_core/core_structs.h"
+#include "src/stdio/printf_core/error_converter.h"
 #include "src/stdio/printf_core/vfprintf_internal.h"
 
 #include "hdr/types/FILE.h"
@@ -29,9 +31,19 @@ LLVM_LIBC_FUNCTION(int, vprintf,
   internal::ArgList args(vlist); // This holder class allows for easier copying
                                  // and pointer semantics, as well as handling
                                  // destruction automatically.
-  int ret_val = printf_core::vfprintf_internal(
+  auto ret_val = printf_core::vfprintf_internal(
       reinterpret_cast<::FILE *>(PRINTF_STDOUT), format, args);
-  return ret_val;
+  if (!ret_val.has_value()) {
+    libc_errno = printf_core::internal_error_to_errno(ret_val.error());
+    return -1;
+  }
+  if (ret_val.value() > cpp::numeric_limits<int>::max()) {
+    libc_errno =
+        printf_core::internal_error_to_errno(-printf_core::OVERFLOW_ERROR);
+    return -1;
+  }
+
+  return static_cast<int>(ret_val.value());
 }
 
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/printf_core/CMakeLists.txt b/libc/src/stdio/printf_core/CMakeLists.txt
index ee66145e60156..016543bbfb535 100644
--- a/libc/src/stdio/printf_core/CMakeLists.txt
+++ b/libc/src/stdio/printf_core/CMakeLists.txt
@@ -32,6 +32,17 @@ if(printf_config_copts)
   list(PREPEND printf_config_copts "COMPILE_OPTIONS")
 endif()
 
+if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+  add_subdirectory(${LIBC_TARGET_OS})
+else()
+  add_subdirectory(generic)
+endif()
+
+set(target_error_converter libc.src.stdio.printf_core.${LIBC_TARGET_OS}.${LIBC_TARGET_OS}_error_converter)
+if(NOT TARGET ${target_error_converter})
+    set(target_error_converter libc.src.stdio.printf_core.generic.generic_error_converter)
+endif()
+
 add_header_library(
   printf_config
   HDRS
@@ -47,6 +58,7 @@ add_header_library(
     libc.include.inttypes
     libc.src.__support.CPP.string_view
     libc.src.__support.FPUtil.fp_bits
+    libc.hdr.errno_macros
 )
 
 add_header_library(
@@ -125,6 +137,7 @@ add_header_library(
     .writer
     .core_structs
     libc.src.__support.arg_list
+    libc.src.__support.error_or
 )
 
 add_header_library(
@@ -136,10 +149,20 @@ add_header_library(
     libc.hdr.func.free
     libc.hdr.func.realloc
     libc.src.__support.arg_list
+    libc.src.__support.error_or
     libc.src.stdio.printf_core.printf_main
     libc.src.stdio.printf_core.writer
 )
 
+add_header_library(
+  error_converter
+  HDRS
+    error_converter.h
+  DEPENDS
+    ${target_error_converter}
+    libc.src.__support.macros.properties.architectures
+)
+
 if(NOT (TARGET libc.src.__support.File.file) AND LLVM_LIBC_FULL_BUILD)
   # Not all platforms have a file implementation. If file is unvailable, and a
   # full build is requested, then we must skip all file based printf sections.
@@ -152,8 +175,10 @@ add_header_library(
     vfprintf_internal.h
   DEPENDS
     libc.src.__support.File.file
+    libc.src.__support.error_or
     libc.src.__support.arg_list
     libc.src.stdio.printf_core.printf_main
     libc.src.stdio.printf_core.writer
   ${use_system_file}
 )
+
diff --git a/libc/src/stdio/printf_core/core_structs.h b/libc/src/stdio/printf_core/core_structs.h
index e27f77b6b594a..0d41f2244d8da 100644
--- a/libc/src/stdio/printf_core/core_structs.h
+++ b/libc/src/stdio/printf_core/core_structs.h
@@ -132,14 +132,17 @@ template <typename T> LIBC_INLINE constexpr TypeDesc type_desc_from_type() {
 
 // This is the value to be returned by conversions when no error has occurred.
 constexpr int WRITE_OK = 0;
-// These are the printf return values for when an error has occurred. They are
-// all negative, and should be distinct.
-constexpr int FILE_WRITE_ERROR = -1;
-constexpr int FILE_STATUS_ERROR = -2;
-constexpr int NULLPTR_WRITE_ERROR = -3;
-constexpr int INT_CONVERSION_ERROR = -4;
-constexpr int FIXED_POINT_CONVERSION_ERROR = -5;
-constexpr int ALLOCATION_ERROR = -6;
+// These are the error return values used by the printf engine when an
+// error has occurred. They are all large negative, distinct values starting
+// from -1000 to not overlap with system errors.
+constexpr int FILE_WRITE_ERROR = -1001;
+constexpr int FILE_STATUS_ERROR = -1002;
+constexpr int NULLPTR_WRITE_ERROR = -1003;
+constexpr int INT_CONVERSION_ERROR = -1004;
+constexpr int FIXED_POINT_CONVERSION_ERROR = -1005;
+constexpr int ALLOCATION_ERROR = -1006;
+constexpr int OVERFLOW_ERROR = -1007;
+
 } // namespace printf_core
 } // namespace LIBC_NAMESPACE_DECL
 
diff --git a/libc/src/stdio/printf_core/darwin/CMakeLists.txt b/libc/src/stdio/printf_core/darwin/CMakeLists.txt
new file mode 100644
index 0000000000000..89bc59097764c
--- /dev/null
+++ b/libc/src/stdio/printf_core/darwin/CMakeLists.txt
@@ -0,0 +1,8 @@
+add_header_library(
+  darwin_error_converter
+  HDRS
+    error_converter.h
+  DEPENDS
+    libc.src.stdio.printf_core.core_structs
+    libc.hdr.errno_macros
+)
diff --git a/libc/src/stdio/printf_core/darwin/error_converter.h b/libc/src/stdio/printf_core/darwin/error_converter.h
new file mode 100644
index 0000000000000..897c76ffe7099
--- /dev/null
+++ b/libc/src/stdio/printf_core/darwin/error_converter.h
@@ -0,0 +1,54 @@
+//===-- Darwin implementation of error converter ----------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_STDIO_PRINTF_CORE_DARWIN_ERROR_CONVERTER_H
+#define LLVM_LIBC_SRC_STDIO_PRINTF_CORE_DARWIN_ERROR_CONVERTER_H
+
+#include "hdr/errno_macros.h"
+#include "src/stdio/printf_core/core_structs.h"
+#include "src/stdio/printf_core/error_converter.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace printf_core {
+
+LIBC_INLINE static int internal_error_to_errno(int internal_error) {
+  // System error occured, return error as is.
+  if (internal_error < 1001 && internal_error > 0) {
+    return internal_error;
+  }
+
+  // Map internal error to POSIX errnos.
+  switch (-internal_error) {
+  case WRITE_OK:
+    return 0;
+  case FILE_WRITE_ERROR:
+    return EIO;
+  case FILE_STATUS_ERROR:
+    return EIO;
+  case NULLPTR_WRITE_ERROR:
+    return EINVAL;
+  case INT_CONVERSION_ERROR:
+    return ERANGE;
+  case FIXED_POINT_CONVERSION_ERROR:
+    return EINVAL;
+  case ALLOCATION_ERROR:
+    return ENOMEM;
+  case OVERFLOW_ERROR:
+    return EOVERFLOW;
+  default:
+    LIBC_ASSERT(
+        false &&
+        "Invalid internal printf error code passed to internal_error_to_errno");
+    return EINVAL;
+  }
+}
+
+} // namespace printf_core
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_STDIO_PRINTF_CORE_DARWIN_ERROR_CONVERTER_H
diff --git a/libc/src/stdio/printf_core/error_converter.h b/libc/src/stdio/printf_core/error_converter.h
new file mode 100644
index 0000000000000..f2fe303203fc7
--- /dev/null
+++ b/libc/src/stdio/printf_core/error_converter.h
@@ -0,0 +1,23 @@
+//===-- Error converter for printf ------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_STDIO_PRINTF_CORE_ERROR_CONVERTER_H
+#define LLVM_LIBC_SRC_STDIO_PRINTF_CORE_ERROR_CONVERTER_H
+
+#include "src/__support/macros/properties/architectures.h"
+
+// Maps internal errors to the available errnos on the platform.
+#if defined(__linux__)
+#include "linux/error_converter.h"
+#elif defined(__APPLE__)
+#include "darwin/error_converter.h"
+#else
+#include "generic/error_converter.h"
+#endif
+
+#endif // LLVM_LIBC_SRC_STDIO_PRINTF_CORE_ERROR_CONVERTER_H
diff --git a/libc/src/stdio/printf_core/generic/CMakeLists.txt b/libc/src/stdio/printf_core/generic/CMakeLists.txt
new file mode 100644
index 0000000000000..f7fc250734645
--- /dev/null
+++ b/libc/src/stdio/printf_core/generic/CMakeLists.txt
@@ -0,0 +1,8 @@
+add_header_library(
+  generic_error_converter
+  HDRS
+    error_converter.h
+  DEPENDS
+    libc.src.stdio.printf_core.core_structs
+    libc.hdr.errno_macros
+)
diff --git a/libc/src/stdio/printf_core/generic/error_converter.h b/libc/src/stdio/printf_core/generic/error_converter.h
new file mode 100644
index 0000000000000..2f59a105415c7
--- /dev/null
+++ b/libc/src/stdio/printf_core/generic/error_converter.h
@@ -0,0 +1,49 @@
+//===-- Generic implementation of error converter ---------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_STDIO_PRINTF_CORE_GENERIC_ERROR_CONVERTER_H
+#define LLVM_LIBC_SRC_STDIO_PRINTF_CORE_GENERIC_ERROR_CONVERTER_H
+
+#include "hdr/errno_macros.h"
+#include "src/stdio/printf_core/core_structs.h"
+#include "src/stdio/printf_core/error_converter.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace printf_core {
+
+LIBC_INLINE static int internal_error_to_errno(int internal_error) {
+  // System error occured, return error as is.
+  if (internal_error < 1001 && internal_error > 0) {
+    return internal_error;
+  }
+
+  // Map internal error to the available C standard errnos.
+  switch (-internal_error) {
+  case WRITE_OK:
+    return 0;
+  case FILE_WRITE_ERROR:
+  case FILE_STATUS_ERROR:
+  case NULLPTR_WRITE_ERROR:
+  case ALLOCATION_ERROR:
+    return EDOM;
+  case INT_CONVERSION_ERROR:
+  case FIXED_POINT_CONVERSION_ERROR:
+  case OVERFLOW_ERROR:
+    return ERANGE;
+  default:
+    LIBC_ASSERT(
+        false &&
+        "Invalid internal printf error code passed to internal_error_to_errno");
+    return EDOM;
+  }
+}
+
+} // namespace printf_core
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_STDIO_PRINTF_CORE_GENERIC_ERROR_CONVERTER_H
diff --git a/libc/src/stdio/printf_core/linux/CMakeLists.txt b/libc/src/stdio/printf_core/linux/CMakeLists.txt
new file mode 100644
index 0000000000000..4b193866a1914
--- /dev/null
+++ b/libc/src/stdio/printf_core/linux/CMakeLists.txt
@@ -0,0 +1,8 @@
+add_header_library(
+  linux_error_converter
+  HDRS
+    error_converter.h
+  DEPENDS
+    libc.src.stdio.printf_core.core_structs
+    libc.hdr.errno_macros
+)
diff --git a/libc/src/stdio/printf_core/linux/error_converter.h b/libc/src/stdio/printf_core/linux/error_converter.h
new file mode 100644
index 0000000000000..9de24858bb3cf
--- /dev/null
+++ b/libc/src/stdio/printf_core/linux/error_converter.h
@@ -0,0 +1,54 @@
+//===-- Linux implementation of error converter -----------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_STDIO_PRINTF_CORE_LINUX_ERROR_CONVERTER_H
+#define LLVM_LIBC_SRC_STDIO_PRINTF_CORE_LINUX_ERROR_CONVERTER_H
+
+#include "hdr/errno_macros.h"
+#include "src/stdio/printf_core/core_structs.h"
+#include "src/stdio/printf_core/error_converter.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace printf_core {
+
+LIBC_INLINE static int internal_error_to_errno(int internal_error) {
+  // System error occured, return error as is.
+  if (internal_error < 1001 && internal_error > 0) {
+    return internal_error;
+  }
+
+  // Map internal error to POSIX errnos.
+  switch (-internal_error) {
+  case WRITE_OK:
+    return 0;
+  case FILE_WRITE_ERROR:
+    return EIO;
+  case FILE_STATUS_ERROR:
+    return EIO;
+  case NULLPTR_WRITE_ERROR:
+    return EINVAL;
+  case INT_CONVERSION_ERROR:
+    return ERANGE;
+  case FIXED_POINT_CONVERSION_ERROR:
+    return EINVAL;
+  case ALLOCATION_ERROR:
+    return ENOMEM;
+  case OVERFLOW_ERROR:
+    return EOVERFLOW;
+  default:
+    LIBC_ASSERT(
+        false &&
+        "Invalid internal printf error code passed to internal_error_to_errno");
+    return EINVAL;
+  }
+}
+
+} // namespace printf_core
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_STDIO_PRINTF_CORE_LINUX_ERROR_CONVERTER_H
diff --git a/libc/src/stdio/printf_core/printf_main.h b/libc/src/stdio/printf_core/printf_main.h
index 57f29858d5298..1c7a7237c097d 100644
--- a/libc/src/stdio/printf_core/printf_main.h
+++ b/libc/src/stdio/printf_core/printf_main.h
@@ -10,6 +10,7 @@
 #define LLVM_LIBC_SRC_STDIO_PRINTF_CORE_PRINTF_MAIN_H
 
 #include "src/__support/arg_list.h"
+#include "src/__support/error_or.h"
 #include "src/__support/macros/config.h"
 #include "src/stdio/printf_core/converter.h"
 #include "src/stdio/printf_core/core_structs.h"
@@ -22,8 +23,9 @@ namespace LIBC_NAMESPACE_DECL {
 namespace printf_core {
 
 template <WriteMode write_mode>
-int printf_main(Writer<write_mode> *writer, const char *__restrict str,
-                internal::ArgList &args) {
+ErrorOr<size_t> printf_main(Writer<write_mode> *writer,
+                            const char *__restrict str,
+                            internal::ArgList &args) {
   Parser<internal::ArgList> parser(str, args);
   int result = 0;
   for (FormatSection cur_section = parser.get_next_section();
@@ -33,9 +35,8 @@ int printf_main(Writer<write_mode> *writer, const char *__restrict str,
       result = convert(writer, cur_section);
     else
       result = writer->write(cur_section.raw_string);
-
     if (result < 0)
-      return result;
+      return Error(-result);
   }
 
   return writer->get_chars_written();
diff --git a/libc/src/stdio/printf_core/vasprintf_internal.h b/libc/src/stdio/printf_core/vasprintf_internal.h
index 283d8df2810fb..41df17b67f35b 100644
--- a/libc/src/stdio/printf_core/vasprintf_internal.h
+++ b/libc/src/stdio/printf_core/vasprintf_internal.h
@@ -10,6 +10,7 @@
 #include "hdr/func/malloc.h"
 #include "hdr/func/realloc.h"
 #include "src/__support/arg_list.h"
+#include "src/__support/error_or.h"
 #include "src/stdio/printf_core/core_structs.h"
 #include "src/stdio/printf_core/printf_main.h"
 #include "src/stdio/printf_core/writer.h"
@@ -29,7 +30,7 @@ LIBC_INLINE int resize_overflow_hook(cpp::string_view new_str, void *target) {
   if (new_buff == nullptr) {
     if (wb->buff != wb->init_buff)
       free(wb->buff);
-    return printf_core::ALLOCATION_ERROR;
+    return ALLOCATION_ERROR;
   }
   if (isBuffOnStack)
     inline_memcpy(new_buff, wb->buff, wb->buff_cur);
@@ -42,27 +43,28 @@ LIBC_INLINE int resize_overflow_hook(cpp::string_view new_str, void *target) {
 
 constexpr size_t DEFAULT_BUFFER_SIZE = 200;
 
-LIBC_INLINE int vasprintf_internal(char **ret, const char *__restrict format,
-                                   internal::ArgList args) {
+LIBC_INLINE ErrorOr<size_t> vasprintf_internal(char **ret,
+                                               const char *__restrict format,
+                                               internal::ArgList args) {
   char init_buff_on_stack[DEFAULT_BUFFER_SIZE];
   printf_core::WriteBuffer<Mode<WriteMode::RESIZE_AND_FILL_BUFF>::value> wb(
       init_buff_on_stack, DEFAULT_BUFFER_SIZE, resize_overflow_hook);
   printf_core::Writer writer(wb);
 
   auto ret_val = printf_core::printf_main(&writer, format, args);
-  if (ret_val < 0) {
+  if (!ret_val.has_value()) {
     *ret = nullptr;
-    return -1;
+    return ret_val;
   }
   if (wb.buff == init_buff_on_stack) {
-    *ret = static_cast<char *>(malloc(ret_val + 1));
+    *ret = static_cast<char *>(malloc(ret_val.value() + 1));
     if (ret == nullptr)
-      return printf_core::ALLOCATION_ERROR;
-    inline_memcpy(*ret, wb.buff, ret_val);
+      return Error(ALLOCATION_ERROR);
+    inline_memcpy(*ret, wb.buff, ret_val.value());
   } else {
     *ret = wb.buff;
   }
-  (*ret)[ret_val] = '\0';
+  (*ret)[ret_val.value()] = '\0';
   return ret_val;
 }
 } // namespace printf_core
diff --git a/libc/src/stdio/printf_core/vfprintf_internal.h b/libc/src/stdio/printf_core/vfprintf_internal.h
index 630de9d9d43dd..4e60248810f27 100644
--- a/libc/src/stdio/printf_core/vfprintf_internal.h
+++ b/libc/src/stdio/printf_core/vfprintf_internal.h
@@ -11,6 +11,7 @@
 
 #include "src/__support/File/file.h"
 #include "src/__support/arg_list.h"
+#include "src/__support/error_or.h"
 #include "src/__support/macros/attributes.h" // For LIBC_INLINE
 #include "src/__support/macros/config.h"
 #include "src/stdio/printf_core/core_structs.h"
@@ -35,8 +36,8 @@ LIBC_INLINE void funlockfile(FILE *f) {
   reinterpret_cast<LIBC_NAMESPACE::File *>(f)->unlock();
 }
 
-LIBC_INLINE size_t fwrite_unlocked(const void *ptr, size_t size, size_t nmemb,
-                                   FILE *f) {
+LIBC_INLINE FileIOResult fwrite_unlocked(const void *ptr, size_t size,
+                                         size_t nmemb, FILE *f) {
   return reinterpret_cast<LIBC_NAMESPACE::File *>(f)->write_unlocked(
       ptr, size * nmemb);
 }
@@ -47,9 +48,9 @@ LIBC_INLINE void flockfile(::FILE *f) { ::flockfile(f); }
 
 LIBC_INLINE void funlockfile(::FILE *f) { ::funlockfile(f); }
 
-LIBC_INLINE size_t fwrite_unlocked(const void *ptr, size_t size, size_t nmemb,
-                                   ::FILE *f) {
-  return ::fwrite_unlocked(ptr, size, nmemb, f);
+LIBC_INLINE FileIOResult fwrite_unlocked(const void *ptr, size_t size,
+                                         size_t nmemb, ::FILE *f) {
+  return {::fwrite_unlocked(ptr, size, nmemb, f), errno};
 }
 #endif // LIBC_COPT_STDIO_USE_SYSTEM_FILE
 } // namespace internal
@@ -60,26 +61,38 @@ LIBC_INLINE int file_write_hook(cpp::string_view new_str, void *fp) {
   ::FILE *target_file = reinterpret_cast<::FILE *>(fp);
   // Write new_str to the target file. The logic preventing a zero-length write
   // is in the writer, so we don't check here.
-  size_t written = internal::fwrite_unlocked(new_str.data(), sizeof(char),
-                                             new_str.size(), target_file);
-  if (written != new_str.size() || internal::ferror_unlocked(target_file))
+  auto write_result = internal::fwrite_unlocked(new_str.data(), sizeof(char),
+                                                new_str.size(), target_file);
+  // Propagate actual system error in FileIOResult.
+  if (write_result.has_error())
+    return -write_result.error;
+
+  // In case short write occured or error was not set on FileIOResult for some
+  // reason.
+  if (write_result.value != new_str.size() ||
+      internal::ferror_unlocked(target_file))
     return FILE_WRITE_ERROR;
+
   return WRITE_OK;
 }
 
-LIBC_INLINE int vfprintf_internal(::FILE *__restrict stream,
-                                  const char *__restrict format,
-                                  internal::ArgList &args) {
+LIBC_INLINE ErrorOr<size_t> vfprintf_internal(::FILE *__restrict stream,
+                                              const char *__restrict format,
+                                              internal::ArgList &args) {
   constexpr size_t BUFF_SIZE = 1024;
   char buffer[BUFF_SIZE];
   printf_core::WriteBuffer<Mode<WriteMode::FLUSH_TO_STREAM>::value> wb(
       buffer, BUFF_SIZE, &file_write_hook, reinterpret_cast<void *>(stream));
   Writer writer(wb);
   internal::flockfile(stream);
-  int retval = printf_main(&writer, format, args);
+  auto retval = printf_main(&writer, format, args);
+  if (!retval.has_value()) {
+    internal::funlockfile(stream);
+    return retval;
+  }
   int flushval = wb.overflow_write("");
   if (flushval != WRITE_OK)
-    retval = flushval;
+    retval = Error(-flushval);
   internal::funlockfile(stream);
   return retval;
 }
diff --git a/libc/src/stdio/printf_core/write_int_converter.h b/libc/src/stdio/printf_core/write_int_converter.h
index efcff278bd284..04b2bef05bc7b 100644
--- a/libc/src/stdio/printf_core/write_int_converter.h
+++ b/libc/src/stdio/printf_core/write_int_converter.h
@@ -29,11 +29,11 @@ LIBC_INLINE int convert_write_int(Writer<write_mode> *writer,
     return NULLPTR_WRITE_ERROR;
 #endif // LIBC_COPT_PRINTF_NO_NULLPTR_CHECKS
 
-  int written = writer->get_chars_written();
+  size_t written = writer->get_chars_written();
 
   switch (to_conv.length_modifier) {
   case LengthModifier::none:
-    *reinterpret_cast<int *>(to_conv.conv_val_ptr) = written;
+    *reinterpret_cast<int *>(to_conv.conv_val_ptr) = static_cast<int>(written);
     break;
   case LengthModifier::l:
     *reinterpret_cast<long *>(to_conv.conv_val_ptr) = written;
diff --git a/libc/src/stdio/printf_core/writer.h b/libc/src/stdio/printf_core/writer.h
index 1d4734a51b9b8..9de108ece510f 100644
--- a/libc/src/stdio/printf_core/writer.h
+++ b/libc/src/stdio/printf_core/writer.h
@@ -127,7 +127,7 @@ template <WriteMode write_mode> struct WriteBuffer {
 
 template <WriteMode write_mode> class Writer final {
   WriteBuffer<write_mode> &wb;
-  int chars_written = 0;
+  size_t chars_written = 0;
 
   LIBC_INLINE int pad(char new_char, size_t length) {
     // First, fill as much of the buffer as possible with the padding char.
@@ -161,7 +161,7 @@ template <WriteMode write_mode> class Writer final {
   // Takes a string, copies it into the buffer if there is space, else passes it
   // to the overflow mechanism to be handled separately.
   LIBC_INLINE int write(cpp::string_view new_string) {
-    chars_written += static_cast<int>(new_string.size());
+    chars_written += new_string.size();
     if (LIBC_LIKELY(wb.buff_cur + new_string.size() <= wb.buff_len)) {
       inline_memcpy(wb.buff + wb.buff_cur, new_string.data(),
                     new_string.size());
@@ -175,7 +175,7 @@ template <WriteMode write_mode> class Writer final {
   // if there is space, else calls pad which will loop and call the overflow
   // mechanism on a secondary buffer.
   LIBC_INLINE int write(char new_char, size_t length) {
-    chars_written += static_cast<int>(length);
+    chars_written += length;
 
     if (LIBC_LIKELY(wb.buff_cur + length <= wb.buff_len)) {
       inline_memset(wb.buff + wb.buff_cur, static_cast<unsigned char>(new_char),
@@ -199,7 +199,7 @@ template <WriteMode write_mode> class Writer final {
     return wb.overflow_write(char_string_view);
   }
 
-  LIBC_INLINE int get_chars_written() { return chars_written; }
+  LIBC_INLINE size_t get_chars_written() { return chars_written; }
 };
 
 // Class-template auto deduction helpers.
diff --git a/libc/src/stdio/snprintf.cpp b/libc/src/stdio/snprintf.cpp
index c8940862f711f..25da3a9dbd2c5 100644
--- a/libc/src/stdio/snprintf.cpp
+++ b/libc/src/stdio/snprintf.cpp
@@ -9,7 +9,10 @@
 #include "src/stdio/snprintf.h"
 
 #include "src/__support/arg_list.h"
+#include "src/__support/libc_errno.h"
 #include "src/__support/macros/config.h"
+#include "src/stdio/printf_core/core_structs.h"
+#include "src/stdio/printf_core/error_converter.h"
 #include "src/stdio/printf_core/printf_main.h"
 #include "src/stdio/printf_core/writer.h"
 
@@ -32,10 +35,21 @@ LLVM_LIBC_FUNCTION(int, snprintf,
       wb(buffer, (buffsz > 0 ? buffsz - 1 : 0));
   printf_core::Writer writer(wb);
 
-  int ret_val = printf_core::printf_main(&writer, format, args);
+  auto ret_val = printf_core::printf_main(&writer, format, args);
+  if (!ret_val.has_value()) {
+    libc_errno = printf_core::internal_error_to_errno(ret_val.error());
+    return -1;
+  }
   if (buffsz > 0) // if the buffsz is 0 the buffer may be a null pointer.
     wb.buff[wb.buff_cur] = '\0';
-  return ret_val;
+
+  if (ret_val.value() > cpp::numeric_limits<int>::max()) {
+    libc_errno =
+        printf_core::internal_error_to_errno(-printf_core::OVERFLOW_ERROR);
+    return -1;
+  }
+
+  return static_cast<int>(ret_val.value());
 }
 
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/sprintf.cpp b/libc/src/stdio/sprintf.cpp
index 7be97d3591aaf..09f222927afd6 100644
--- a/libc/src/stdio/sprintf.cpp
+++ b/libc/src/stdio/sprintf.cpp
@@ -10,7 +10,10 @@
 
 #include "src/__support/CPP/limits.h"
 #include "src/__support/arg_list.h"
+#include "src/__support/libc_errno.h"
 #include "src/__support/macros/config.h"
+#include "src/stdio/printf_core/core_structs.h"
+#include "src/stdio/printf_core/error_converter.h"
 #include "src/stdio/printf_core/printf_main.h"
 #include "src/stdio/printf_core/writer.h"
 
@@ -33,9 +36,20 @@ LLVM_LIBC_FUNCTION(int, sprintf,
       wb(buffer, cpp::numeric_limits<size_t>::max());
   printf_core::Writer writer(wb);
 
-  int ret_val = printf_core::printf_main(&writer, format, args);
+  auto ret_val = printf_core::printf_main(&writer, format, args);
+  if (!ret_val.has_value()) {
+    libc_errno = printf_core::internal_error_to_errno(ret_val.error());
+    return -1;
+  }
   wb.buff[wb.buff_cur] = '\0';
-  return ret_val;
+
+  if (ret_val.value() > cpp::numeric_limits<int>::max()) {
+    libc_errno =
+        printf_core::internal_error_to_errno(-printf_core::OVERFLOW_ERROR);
+    return -1;
+  }
+
+  return static_cast<int>(ret_val.value());
 }
 
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/vasprintf.cpp b/libc/src/stdio/vasprintf.cpp
index 4a44d4a0f8842..d1ac9f4342824 100644
--- a/libc/src/stdio/vasprintf.cpp
+++ b/libc/src/stdio/vasprintf.cpp
@@ -8,6 +8,9 @@
 
 #include "src/stdio/vasprintf.h"
 #include "src/__support/arg_list.h"
+#include "src/__support/libc_errno.h"
+#include "src/stdio/printf_core/core_structs.h"
+#include "src/stdio/printf_core/error_converter.h"
 #include "src/stdio/printf_core/vasprintf_internal.h"
 
 namespace LIBC_NAMESPACE_DECL {
@@ -18,7 +21,17 @@ LLVM_LIBC_FUNCTION(int, vasprintf,
   internal::ArgList args(vlist); // This holder class allows for easier copying
                                  // and pointer semantics, as well as handling
                                  // destruction automatically.
-  return printf_core::vasprintf_internal(ret, format, args);
+  auto ret_val = printf_core::vasprintf_internal(ret, format, args);
+  if (!ret_val.has_value()) {
+    libc_errno = printf_core::internal_error_to_errno(ret_val.error());
+    return -1;
+  }
+  if (ret_val.value() > cpp::numeric_limits<int>::max()) {
+    libc_errno =
+        printf_core::internal_error_to_errno(-printf_core::OVERFLOW_ERROR);
+    return -1;
+  }
+  return static_cast<int>(ret_val.value());
 }
 
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/vsnprintf.cpp b/libc/src/stdio/vsnprintf.cpp
index b07a2499a0dd3..01ece7d04df7e 100644
--- a/libc/src/stdio/vsnprintf.cpp
+++ b/libc/src/stdio/vsnprintf.cpp
@@ -9,7 +9,10 @@
 #include "src/stdio/vsnprintf.h"
 
 #include "src/__support/arg_list.h"
+#include "src/__support/libc_errno.h"
 #include "src/__support/macros/config.h"
+#include "src/stdio/printf_core/core_structs.h"
+#include "src/stdio/printf_core/error_converter.h"
 #include "src/stdio/printf_core/printf_main.h"
 #include "src/stdio/printf_core/writer.h"
 
@@ -29,10 +32,21 @@ LLVM_LIBC_FUNCTION(int, vsnprintf,
       wb(buffer, (buffsz > 0 ? buffsz - 1 : 0));
   printf_core::Writer writer(wb);
 
-  int ret_val = printf_core::printf_main(&writer, format, args);
+  auto ret_val = printf_core::printf_main(&writer, format, args);
+  if (!ret_val.has_value()) {
+    libc_errno = printf_core::internal_error_to_errno(ret_val.error());
+    return -1;
+  }
   if (buffsz > 0) // if the buffsz is 0 the buffer may be a null pointer.
     wb.buff[wb.buff_cur] = '\0';
-  return ret_val;
+
+  if (ret_val.value() > cpp::numeric_limits<int>::max()) {
+    libc_errno =
+        printf_core::internal_error_to_errno(-printf_core::OVERFLOW_ERROR);
+    return -1;
+  }
+
+  return static_cast<int>(ret_val.value());
 }
 
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/vsprintf.cpp b/libc/src/stdio/vsprintf.cpp
index 26d497be42125..3b1a4a37bc405 100644
--- a/libc/src/stdio/vsprintf.cpp
+++ b/libc/src/stdio/vsprintf.cpp
@@ -10,7 +10,10 @@
 
 #include "src/__support/CPP/limits.h"
 #include "src/__support/arg_list.h"
+#include "src/__support/libc_errno.h"
 #include "src/__support/macros/config.h"
+#include "src/stdio/printf_core/core_structs.h"
+#include "src/stdio/printf_core/error_converter.h"
 #include "src/stdio/printf_core/printf_main.h"
 #include "src/stdio/printf_core/writer.h"
 
@@ -30,9 +33,19 @@ LLVM_LIBC_FUNCTION(int, vsprintf,
       wb(buffer, cpp::numeric_limits<size_t>::max());
   printf_core::Writer writer(wb);
 
-  int ret_val = printf_core::printf_main(&writer, format, args);
+  auto ret_val = printf_core::printf_main(&writer, format, args);
+  if (!ret_val.has_value()) {
+    libc_errno = printf_core::internal_error_to_errno(ret_val.error());
+    return -1;
+  }
   wb.buff[wb.buff_cur] = '\0';
-  return ret_val;
+
+  if (ret_val.value() > cpp::numeric_limits<int>::max()) {
+    libc_errno =
+        printf_core::internal_error_to_errno(-printf_core::OVERFLOW_ERROR);
+    return -1;
+  }
+  return static_cast<int>(ret_val.value());
 }
 
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdlib/CMakeLists.txt b/libc/src/stdlib/CMakeLists.txt
index c464f82dcbda7..379fb39424f55 100644
--- a/libc/src/stdlib/CMakeLists.txt
+++ b/libc/src/stdlib/CMakeLists.txt
@@ -73,6 +73,7 @@ add_entrypoint_object(
     strfromf.h
   DEPENDS
     .str_from_util
+    libc.src.stdio.printf_core.error_converter
 )
 
 add_entrypoint_object(
@@ -83,6 +84,7 @@ add_entrypoint_object(
     strfromd.h
   DEPENDS
     .str_from_util
+    libc.src.stdio.printf_core.error_converter
 )
 
 add_entrypoint_object(
@@ -93,6 +95,7 @@ add_entrypoint_object(
     strfroml.h
   DEPENDS
     .str_from_util
+    libc.src.stdio.printf_core.error_converter
 )
 
 add_header_library(
diff --git a/libc/src/stdlib/strfromd.cpp b/libc/src/stdlib/strfromd.cpp
index f51e6d4c7f1df..dce1b5e5f253f 100644
--- a/libc/src/stdlib/strfromd.cpp
+++ b/libc/src/stdlib/strfromd.cpp
@@ -8,6 +8,8 @@
 
 #include "src/stdlib/strfromd.h"
 #include "src/__support/macros/config.h"
+#include "src/stdio/printf_core/core_structs.h"
+#include "src/stdio/printf_core/error_converter.h"
 #include "src/stdlib/str_from_util.h"
 
 namespace LIBC_NAMESPACE_DECL {
@@ -36,7 +38,12 @@ LLVM_LIBC_FUNCTION(int, strfromd,
   if (n > 0)
     wb.buff[wb.buff_cur] = '\0';
 
-  return writer.get_chars_written();
+  if (writer.get_chars_written() > cpp::numeric_limits<int>::max()) {
+    libc_errno =
+        printf_core::internal_error_to_errno(-printf_core::OVERFLOW_ERROR);
+    return -1;
+  }
+  return static_cast<int>(writer.get_chars_written());
 }
 
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdlib/strfromf.cpp b/libc/src/stdlib/strfromf.cpp
index 14dbfdb25bab6..fe811ee27242f 100644
--- a/libc/src/stdlib/strfromf.cpp
+++ b/libc/src/stdlib/strfromf.cpp
@@ -8,6 +8,8 @@
 
 #include "src/stdlib/strfromf.h"
 #include "src/__support/macros/config.h"
+#include "src/stdio/printf_core/core_structs.h"
+#include "src/stdio/printf_core/error_converter.h"
 #include "src/stdlib/str_from_util.h"
 
 namespace LIBC_NAMESPACE_DECL {
@@ -36,7 +38,12 @@ LLVM_LIBC_FUNCTION(int, strfromf,
   if (n > 0)
     wb.buff[wb.buff_cur] = '\0';
 
-  return writer.get_chars_written();
+  if (writer.get_chars_written() > cpp::numeric_limits<int>::max()) {
+    libc_errno =
+        printf_core::internal_error_to_errno(-printf_core::OVERFLOW_ERROR);
+    return -1;
+  }
+  return static_cast<int>(writer.get_chars_written());
 }
 
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdlib/strfroml.cpp b/libc/src/stdlib/strfroml.cpp
index 12f22a8a2fb65..ef27312d026c2 100644
--- a/libc/src/stdlib/strfroml.cpp
+++ b/libc/src/stdlib/strfroml.cpp
@@ -8,6 +8,8 @@
 
 #include "src/stdlib/strfroml.h"
 #include "src/__support/macros/config.h"
+#include "src/stdio/printf_core/core_structs.h"
+#include "src/stdio/printf_core/error_converter.h"
 #include "src/stdlib/str_from_util.h"
 
 namespace LIBC_NAMESPACE_DECL {
@@ -41,7 +43,12 @@ LLVM_LIBC_FUNCTION(int, strfroml,
   if (n > 0)
     wb.buff[wb.buff_cur] = '\0';
 
-  return writer.get_chars_written();
+  if (writer.get_chars_written() > cpp::numeric_limits<int>::max()) {
+    libc_errno =
+        printf_core::internal_error_to_errno(-printf_core::OVERFLOW_ERROR);
+    return -1;
+  }
+  return static_cast<int>(writer.get_chars_written());
 }
 
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/time/strftime_core/strftime_main.h b/libc/src/time/strftime_core/strftime_main.h
index c7e590627094a..2b136d83234cd 100644
--- a/libc/src/time/strftime_core/strftime_main.h
+++ b/libc/src/time/strftime_core/strftime_main.h
@@ -36,7 +36,8 @@ int strftime_main(printf_core::Writer<write_mode> *writer,
       return result;
   }
 
-  return writer->get_chars_written();
+  // TODO: Use ErrorOr<size_t>
+  return static_cast<int>(writer->get_chars_written());
 }
 
 } // namespace strftime_core
diff --git a/libc/test/src/stdio/CMakeLists.txt b/libc/test/src/stdio/CMakeLists.txt
index eec108bc12ca5..d71f1dff11943 100644
--- a/libc/test/src/stdio/CMakeLists.txt
+++ b/libc/test/src/stdio/CMakeLists.txt
@@ -186,6 +186,8 @@ add_libc_test(
     fprintf_test.cpp
   DEPENDS
     libc.src.stdio.fprintf
+    libc.test.UnitTest.ErrnoCheckingTest
+    libc.test.UnitTest.ErrnoSetterMatcher
     ${fprintf_test_deps}
   COMPILE_OPTIONS
     ${use_system_file}
diff --git a/libc/test/src/stdio/fprintf_test.cpp b/libc/test/src/stdio/fprintf_test.cpp
index 6799323cc6ad9..1d081f00a31a4 100644
--- a/libc/test/src/stdio/fprintf_test.cpp
+++ b/libc/test/src/stdio/fprintf_test.cpp
@@ -15,6 +15,9 @@
 
 #include "src/stdio/fprintf.h"
 
+#include "src/__support/CPP/limits.h"
+#include "test/UnitTest/ErrnoCheckingTest.h"
+#include "test/UnitTest/ErrnoSetterMatcher.h"
 #include "test/UnitTest/Test.h"
 
 namespace printf_test {
@@ -31,6 +34,8 @@ using ::fread;
 #endif // LIBC_COPT_STDIO_USE_SYSTEM_FILE
 } // namespace printf_test
 
+using LlvmLibcFPrintfTest = LIBC_NAMESPACE::testing::ErrnoCheckingTest;
+
 TEST(LlvmLibcFPrintfTest, WriteToFile) {
   const char *FILENAME = APPEND_LIBC_TEST("fprintf_output.test");
   auto FILE_PATH = libc_make_test_file_path(FILENAME);
@@ -78,6 +83,23 @@ TEST(LlvmLibcFPrintfTest, WriteToFile) {
   written =
       LIBC_NAMESPACE::fprintf(file, "Writing to a read only file should fail.");
   EXPECT_LT(written, 0);
+  ASSERT_ERRNO_EQ(EBADF);
+
+  ASSERT_EQ(printf_test::fclose(file), 0);
+}
+
+#ifndef LIBC_COPT_PRINTF_NO_NULLPTR_CHECKS
+TEST(LlvmLibcFPrintfTest, NullPtrCheck) {
+  const char *FILENAME = APPEND_LIBC_TEST("fprintf_nullptr.test");
+  auto FILE_PATH = libc_make_test_file_path(FILENAME);
+
+  ::FILE *file = printf_test::fopen(FILE_PATH, "w");
+  ASSERT_FALSE(file == nullptr);
+
+  int ret = LIBC_NAMESPACE::fprintf(file, "hello %n", (int *)nullptr);
+  EXPECT_LT(ret, 0);
+  ASSERT_ERRNO_EQ(EINVAL);
 
   ASSERT_EQ(printf_test::fclose(file), 0);
 }
+#endif // LIBC_COPT_PRINTF_NO_NULLPTR_CHECKS
diff --git a/libc/test/src/stdio/printf_core/converter_test.cpp b/libc/test/src/stdio/printf_core/converter_test.cpp
index bf088937e4104..2dae2a22c864c 100644
--- a/libc/test/src/stdio/printf_core/converter_test.cpp
+++ b/libc/test/src/stdio/printf_core/converter_test.cpp
@@ -38,7 +38,7 @@ TEST_F(LlvmLibcPrintfConverterTest, SimpleRawConversion) {
   wb.buff[wb.buff_cur] = '\0';
 
   ASSERT_STREQ(str, "abc");
-  ASSERT_EQ(writer.get_chars_written(), 3);
+  ASSERT_EQ(writer.get_chars_written(), size_t{3});
 }
 
 TEST_F(LlvmLibcPrintfConverterTest, PercentConversion) {
@@ -52,7 +52,7 @@ TEST_F(LlvmLibcPrintfConverterTest, PercentConversion) {
   wb.buff[wb.buff_cur] = '\0';
 
   ASSERT_STREQ(str, "%");
-  ASSERT_EQ(writer.get_chars_written(), 1);
+  ASSERT_EQ(writer.get_chars_written(), size_t{1});
 }
 
 TEST_F(LlvmLibcPrintfConverterTest, CharConversionSimple) {
@@ -70,7 +70,7 @@ TEST_F(LlvmLibcPrintfConverterTest, CharConversionSimple) {
   wb.buff[wb.buff_cur] = '\0';
 
   ASSERT_STREQ(str, "D");
-  ASSERT_EQ(writer.get_chars_written(), 1);
+  ASSERT_EQ(writer.get_chars_written(), size_t{1});
 }
 
 TEST_F(LlvmLibcPrintfConverterTest, CharConversionRightJustified) {
@@ -85,7 +85,7 @@ TEST_F(LlvmLibcPrintfConverterTest, CharConversionRightJustified) {
   wb.buff[wb.buff_cur] = '\0';
 
   ASSERT_STREQ(str, "   E");
-  ASSERT_EQ(writer.get_chars_written(), 4);
+  ASSERT_EQ(writer.get_chars_written(), size_t{4});
 }
 
 TEST_F(LlvmLibcPrintfConverterTest, CharConversionLeftJustified) {
@@ -102,7 +102,7 @@ TEST_F(LlvmLibcPrintfConverterTest, CharConversionLeftJustified) {
   wb.buff[wb.buff_cur] = '\0';
 
   ASSERT_STREQ(str, "F   ");
-  ASSERT_EQ(writer.get_chars_written(), 4);
+  ASSERT_EQ(writer.get_chars_written(), size_t{4});
 }
 
 TEST_F(LlvmLibcPrintfConverterTest, StringConversionSimple) {
@@ -118,7 +118,7 @@ TEST_F(LlvmLibcPrintfConverterTest, StringConversionSimple) {
   wb.buff[wb.buff_cur] = '\0';
 
   ASSERT_STREQ(str, "DEF");
-  ASSERT_EQ(writer.get_chars_written(), 3);
+  ASSERT_EQ(writer.get_chars_written(), size_t{3});
 }
 
 TEST_F(LlvmLibcPrintfConverterTest, StringConversionPrecisionHigh) {
@@ -133,7 +133,7 @@ TEST_F(LlvmLibcPrintfConverterTest, StringConversionPrecisionHigh) {
   wb.buff[wb.buff_cur] = '\0';
 
   ASSERT_STREQ(str, "456");
-  ASSERT_EQ(writer.get_chars_written(), 3);
+  ASSERT_EQ(writer.get_chars_written(), size_t{3});
 }
 
 TEST_F(LlvmLibcPrintfConverterTest, StringConversionPrecisionLow) {
@@ -148,7 +148,7 @@ TEST_F(LlvmLibcPrintfConverterTest, StringConversionPrecisionLow) {
   wb.buff[wb.buff_cur] = '\0';
 
   ASSERT_STREQ(str, "xy");
-  ASSERT_EQ(writer.get_chars_written(), 2);
+  ASSERT_EQ(writer.get_chars_written(), size_t{2});
 }
 
 TEST_F(LlvmLibcPrintfConverterTest, StringConversionRightJustified) {
@@ -163,7 +163,7 @@ TEST_F(LlvmLibcPrintfConverterTest, StringConversionRightJustified) {
   wb.buff[wb.buff_cur] = '\0';
 
   ASSERT_STREQ(str, " 789");
-  ASSERT_EQ(writer.get_chars_written(), 4);
+  ASSERT_EQ(writer.get_chars_written(), size_t{4});
 }
 
 TEST_F(LlvmLibcPrintfConverterTest, StringConversionLeftJustified) {
@@ -180,7 +180,7 @@ TEST_F(LlvmLibcPrintfConverterTest, StringConversionLeftJustified) {
   wb.buff[wb.buff_cur] = '\0';
 
   ASSERT_STREQ(str, "ghi ");
-  ASSERT_EQ(writer.get_chars_written(), 4);
+  ASSERT_EQ(writer.get_chars_written(), size_t{4});
 }
 
 TEST_F(LlvmLibcPrintfConverterTest, IntConversionSimple) {
@@ -194,7 +194,7 @@ TEST_F(LlvmLibcPrintfConverterTest, IntConversionSimple) {
   wb.buff[wb.buff_cur] = '\0';
 
   ASSERT_STREQ(str, "12345");
-  ASSERT_EQ(writer.get_chars_written(), 5);
+  ASSERT_EQ(writer.get_chars_written(), size_t{5});
 }
 
 TEST_F(LlvmLibcPrintfConverterTest, HexConversion) {
@@ -211,7 +211,7 @@ TEST_F(LlvmLibcPrintfConverterTest, HexConversion) {
 
   wb.buff[wb.buff_cur] = '\0';
   ASSERT_STREQ(str, "0x00000000123456ab");
-  ASSERT_EQ(writer.get_chars_written(), 18);
+  ASSERT_EQ(writer.get_chars_written(), size_t{18});
 }
 
 TEST_F(LlvmLibcPrintfConverterTest, BinaryConversion) {
@@ -225,7 +225,7 @@ TEST_F(LlvmLibcPrintfConverterTest, BinaryConversion) {
   wb.buff[wb.buff_cur] = '\0';
 
   ASSERT_STREQ(str, "101010");
-  ASSERT_EQ(writer.get_chars_written(), 6);
+  ASSERT_EQ(writer.get_chars_written(), size_t{6});
 }
 
 TEST_F(LlvmLibcPrintfConverterTest, PointerConversion) {
@@ -239,7 +239,7 @@ TEST_F(LlvmLibcPrintfConverterTest, PointerConversion) {
 
   wb.buff[wb.buff_cur] = '\0';
   ASSERT_STREQ(str, "0x123456ab");
-  ASSERT_EQ(writer.get_chars_written(), 10);
+  ASSERT_EQ(writer.get_chars_written(), size_t{10});
 }
 
 TEST_F(LlvmLibcPrintfConverterTest, OctConversion) {
@@ -253,5 +253,5 @@ TEST_F(LlvmLibcPrintfConverterTest, OctConversion) {
 
   wb.buff[wb.buff_cur] = '\0';
   ASSERT_STREQ(str, "1234");
-  ASSERT_EQ(writer.get_chars_written(), 4);
+  ASSERT_EQ(writer.get_chars_written(), size_t{4});
 }
diff --git a/libc/test/src/stdio/printf_core/writer_test.cpp b/libc/test/src/stdio/printf_core/writer_test.cpp
index d036341be7981..d263cf55aa474 100644
--- a/libc/test/src/stdio/printf_core/writer_test.cpp
+++ b/libc/test/src/stdio/printf_core/writer_test.cpp
@@ -39,7 +39,7 @@ TEST(LlvmLibcPrintfWriterTest, Write) {
   wb.buff[wb.buff_cur] = '\0';
 
   ASSERT_STREQ("abc", str);
-  ASSERT_EQ(writer.get_chars_written(), 3);
+  ASSERT_EQ(writer.get_chars_written(), size_t{3});
 }
 
 TEST(LlvmLibcPrintfWriterTest, WriteMultipleTimes) {
@@ -53,7 +53,7 @@ TEST(LlvmLibcPrintfWriterTest, WriteMultipleTimes) {
   wb.buff[wb.buff_cur] = '\0';
 
   ASSERT_STREQ("abcDEF123", str);
-  ASSERT_EQ(writer.get_chars_written(), 9);
+  ASSERT_EQ(writer.get_chars_written(), size_t{9});
 }
 
 TEST(LlvmLibcPrintfWriterTest, WriteChars) {
@@ -66,7 +66,7 @@ TEST(LlvmLibcPrintfWriterTest, WriteChars) {
   wb.buff[wb.buff_cur] = '\0';
 
   ASSERT_STREQ("aaa", str);
-  ASSERT_EQ(writer.get_chars_written(), 3);
+  ASSERT_EQ(writer.get_chars_written(), size_t{3});
 }
 
 TEST(LlvmLibcPrintfWriterTest, WriteCharsMultipleTimes) {
@@ -80,7 +80,7 @@ TEST(LlvmLibcPrintfWriterTest, WriteCharsMultipleTimes) {
   wb.buff[wb.buff_cur] = '\0';
 
   ASSERT_STREQ("aaaDDD111", str);
-  ASSERT_EQ(writer.get_chars_written(), 9);
+  ASSERT_EQ(writer.get_chars_written(), size_t{9});
 }
 
 TEST(LlvmLibcPrintfWriterTest, WriteManyChars) {
@@ -102,7 +102,7 @@ TEST(LlvmLibcPrintfWriterTest, WriteManyChars) {
                "ZZZZZZZZZZ"
                "ZZZZZZZZZ",
                str);
-  ASSERT_EQ(writer.get_chars_written(), 99);
+  ASSERT_EQ(writer.get_chars_written(), size_t{99});
 }
 
 TEST(LlvmLibcPrintfWriterTest, MixedWrites) {
@@ -117,7 +117,7 @@ TEST(LlvmLibcPrintfWriterTest, MixedWrites) {
   wb.buff[wb.buff_cur] = '\0';
 
   ASSERT_STREQ("aaaDEF111456", str);
-  ASSERT_EQ(writer.get_chars_written(), 12);
+  ASSERT_EQ(writer.get_chars_written(), size_t{12});
 }
 
 TEST(LlvmLibcPrintfWriterTest, WriteWithMaxLength) {
@@ -129,7 +129,7 @@ TEST(LlvmLibcPrintfWriterTest, WriteWithMaxLength) {
   wb.buff[wb.buff_cur] = '\0';
 
   ASSERT_STREQ("abcDEF1234", str);
-  ASSERT_EQ(writer.get_chars_written(), 12);
+  ASSERT_EQ(writer.get_chars_written(), size_t{12});
 }
 
 TEST(LlvmLibcPrintfWriterTest, WriteCharsWithMaxLength) {
@@ -141,7 +141,7 @@ TEST(LlvmLibcPrintfWriterTest, WriteCharsWithMaxLength) {
   wb.buff[wb.buff_cur] = '\0';
 
   ASSERT_STREQ("1111111111", str);
-  ASSERT_EQ(writer.get_chars_written(), 15);
+  ASSERT_EQ(writer.get_chars_written(), size_t{15});
 }
 
 TEST(LlvmLibcPrintfWriterTest, MixedWriteWithMaxLength) {
@@ -157,7 +157,7 @@ TEST(LlvmLibcPrintfWriterTest, MixedWriteWithMaxLength) {
   wb.buff[wb.buff_cur] = '\0';
 
   ASSERT_STREQ("aaaDEF1114", str);
-  ASSERT_EQ(writer.get_chars_written(), 12);
+  ASSERT_EQ(writer.get_chars_written(), size_t{12});
 }
 
 TEST(LlvmLibcPrintfWriterTest, StringWithMaxLengthOne) {
@@ -175,7 +175,7 @@ TEST(LlvmLibcPrintfWriterTest, StringWithMaxLengthOne) {
   wb.buff[wb.buff_cur] = '\0';
 
   ASSERT_STREQ("", str);
-  ASSERT_EQ(writer.get_chars_written(), 12);
+  ASSERT_EQ(writer.get_chars_written(), size_t{12});
 }
 
 TEST(LlvmLibcPrintfWriterTest, NullStringWithZeroMaxLength) {
@@ -187,7 +187,7 @@ TEST(LlvmLibcPrintfWriterTest, NullStringWithZeroMaxLength) {
   writer.write('1', 3);
   writer.write({"456", 3});
 
-  ASSERT_EQ(writer.get_chars_written(), 12);
+  ASSERT_EQ(writer.get_chars_written(), size_t{12});
 }
 
 struct OutBuff {
@@ -226,7 +226,7 @@ TEST(LlvmLibcPrintfWriterTest, WriteWithMaxLengthWithCallback) {
   str[out_buff.cur_pos] = '\0';
 
   ASSERT_STREQ("abcDEF123456", str);
-  ASSERT_EQ(writer.get_chars_written(), 12);
+  ASSERT_EQ(writer.get_chars_written(), size_t{12});
 }
 
 TEST(LlvmLibcPrintfWriterTest, WriteCharsWithMaxLengthWithCallback) {
@@ -246,7 +246,7 @@ TEST(LlvmLibcPrintfWriterTest, WriteCharsWithMaxLengthWithCallback) {
   str[out_buff.cur_pos] = '\0';
 
   ASSERT_STREQ("111111111111111", str);
-  ASSERT_EQ(writer.get_chars_written(), 15);
+  ASSERT_EQ(writer.get_chars_written(), size_t{15});
 }
 
 TEST(LlvmLibcPrintfWriterTest, MixedWriteWithMaxLengthWithCallback) {
@@ -269,7 +269,7 @@ TEST(LlvmLibcPrintfWriterTest, MixedWriteWithMaxLengthWithCallback) {
   str[out_buff.cur_pos] = '\0';
 
   ASSERT_STREQ("aaaDEF111456", str);
-  ASSERT_EQ(writer.get_chars_written(), 12);
+  ASSERT_EQ(writer.get_chars_written(), size_t{12});
 }
 
 TEST(LlvmLibcPrintfWriterTest, ZeroLengthBufferWithCallback) {
@@ -292,7 +292,7 @@ TEST(LlvmLibcPrintfWriterTest, ZeroLengthBufferWithCallback) {
   str[out_buff.cur_pos] = '\0';
 
   ASSERT_STREQ("aaaDEF111456", str);
-  ASSERT_EQ(writer.get_chars_written(), 12);
+  ASSERT_EQ(writer.get_chars_written(), size_t{12});
 }
 
 TEST(LlvmLibcPrintfWriterTest, NullStringWithZeroMaxLengthWithCallback) {
@@ -312,7 +312,7 @@ TEST(LlvmLibcPrintfWriterTest, NullStringWithZeroMaxLengthWithCallback) {
   wb.overflow_write("");
   str[out_buff.cur_pos] = '\0';
 
-  ASSERT_EQ(writer.get_chars_written(), 12);
+  ASSERT_EQ(writer.get_chars_written(), size_t{12});
   ASSERT_STREQ("aaaDEF111456", str);
 }
 
diff --git a/libc/test/src/stdio/snprintf_test.cpp b/libc/test/src/stdio/snprintf_test.cpp
index baaa664cdc9ee..1062f952d7429 100644
--- a/libc/test/src/stdio/snprintf_test.cpp
+++ b/libc/test/src/stdio/snprintf_test.cpp
@@ -8,8 +8,12 @@
 
 #include "src/stdio/snprintf.h"
 
+#include "test/UnitTest/ErrnoCheckingTest.h"
+#include "test/UnitTest/ErrnoSetterMatcher.h"
 #include "test/UnitTest/Test.h"
 
+using LlvmLibcSNPrintfTest = LIBC_NAMESPACE::testing::ErrnoCheckingTest;
+
 // The sprintf test cases cover testing the shared printf functionality, so
 // these tests will focus on snprintf exclusive features.
 
@@ -59,3 +63,14 @@ TEST(LlvmLibcSNPrintfTest, NoCutOff) {
   EXPECT_EQ(written, 10);
   ASSERT_STREQ(buff, "1234567890");
 }
+
+TEST(LlvmLibcSNPrintfTest, CharsWrittenOverflow) {
+  char buff[0];
+
+  // Trigger an overflow in the return value of snprintf by writing more than
+  // INT_MAX bytes.
+  int int_max = LIBC_NAMESPACE::cpp::numeric_limits<int>::max();
+  int written = LIBC_NAMESPACE::snprintf(buff, 0, "%*stest", int_max, "");
+  EXPECT_LT(written, 0);
+  ASSERT_ERRNO_EQ(EOVERFLOW);
+}
diff --git a/libc/test/src/stdio/vfprintf_test.cpp b/libc/test/src/stdio/vfprintf_test.cpp
index f50565a0f68ca..9b5f09db8fd41 100644
--- a/libc/test/src/stdio/vfprintf_test.cpp
+++ b/libc/test/src/stdio/vfprintf_test.cpp
@@ -19,6 +19,8 @@
 
 #include "src/stdio/vfprintf.h"
 
+#include "test/UnitTest/ErrnoCheckingTest.h"
+#include "test/UnitTest/ErrnoSetterMatcher.h"
 #include "test/UnitTest/Test.h"
 
 namespace printf_test {
@@ -44,6 +46,8 @@ int call_vfprintf(::FILE *__restrict stream, const char *__restrict format,
   return ret;
 }
 
+using LlvmLibcVFPrintfTest = LIBC_NAMESPACE::testing::ErrnoCheckingTest;
+
 TEST(LlvmLibcVFPrintfTest, WriteToFile) {
   const char *FILENAME = APPEND_LIBC_TEST("vfprintf_output.test");
   auto FILE_PATH = libc_make_test_file_path(FILENAME);
@@ -90,6 +94,7 @@ TEST(LlvmLibcVFPrintfTest, WriteToFile) {
 
   written = call_vfprintf(file, "Writing to a read only file should fail.");
   EXPECT_LT(written, 0);
+  ASSERT_ERRNO_EQ(EBADF);
 
   ASSERT_EQ(printf_test::fclose(file), 0);
 }
diff --git a/libc/test/src/stdlib/StrfromTest.h b/libc/test/src/stdlib/StrfromTest.h
index e82c94499aa11..fdeed0e3c06f5 100644
--- a/libc/test/src/stdlib/StrfromTest.h
+++ b/libc/test/src/stdlib/StrfromTest.h
@@ -8,6 +8,8 @@
 
 #include "src/__support/CPP/type_traits.h"
 #include "src/__support/FPUtil/FPBits.h"
+#include "test/UnitTest/ErrnoCheckingTest.h"
+#include "test/UnitTest/ErrnoSetterMatcher.h"
 #include "test/UnitTest/Test.h"
 
 #define ASSERT_STREQ_LEN(actual_written, actual_str, expected_str)             \
@@ -15,7 +17,7 @@
   EXPECT_STREQ(actual_str, expected_str);
 
 template <typename InputT>
-class StrfromTest : public LIBC_NAMESPACE::testing::Test {
+class StrfromTest : public LIBC_NAMESPACE::testing::ErrnoCheckingTest {
 
   static constexpr bool is_single_prec =
       LIBC_NAMESPACE::cpp::is_same<InputT, float>::value;
@@ -481,6 +483,16 @@ class StrfromTest : public LIBC_NAMESPACE::testing::Test {
     written = func(buff, 10, "%A", -ld_nan);
     ASSERT_STREQ_LEN(written, buff, "-NAN");
   }
+
+  void charsWrittenOverflow(FunctionT func) {
+    char buff[100];
+    // Trigger an overflow in the return value of strfrom by writing more than
+    // INT_MAX bytes.
+    int result = func(buff, sizeof(buff), "%.2147483647f", 1.0f);
+
+    EXPECT_LT(result, 0);
+    ASSERT_ERRNO_EQ(EOVERFLOW);
+  }
 };
 
 #define STRFROM_TEST(InputType, name, func)                                    \
@@ -501,4 +513,7 @@ class StrfromTest : public LIBC_NAMESPACE::testing::Test {
   TEST_F(LlvmLibc##name##Test, InsufficientBufferSize) {                       \
     insufficentBufsize(func);                                                  \
   }                                                                            \
-  TEST_F(LlvmLibc##name##Test, InfAndNanValues) { infNanValues(func); }
+  TEST_F(LlvmLibc##name##Test, InfAndNanValues) { infNanValues(func); }        \
+  TEST_F(LlvmLibc##name##Test, CharsWrittenOverflow) {                         \
+    charsWrittenOverflow(func);                                                \
+  }