[libc] Add C23 limits.h header. (#78887)

Author: lntue

libc/cmake/modules/LLVMLibCLibraryRules.cmake

@@ -173,7 +173,17 @@ function(create_header_library fq_target_name)
   target_sources(${fq_target_name} INTERFACE ${ADD_HEADER_HDRS})
   if(ADD_HEADER_DEPENDS)
     add_dependencies(${fq_target_name} ${ADD_HEADER_DEPENDS})
-    target_link_libraries(${fq_target_name} INTERFACE ${ADD_HEADER_DEPENDS})
+
+    # `*.__copied_hdr__` is created only to copy the header files to the target
+    # location, not to be linked against.
+    set(link_lib "")
+    foreach(dep ${ADD_HEADER_DEPENDS})
+      if (NOT dep MATCHES "__copied_hdr__")
+        list(APPEND link_lib ${dep})
+      endif()
+    endforeach()
+
+    target_link_libraries(${fq_target_name} INTERFACE ${link_lib})
   endif()
   if(ADD_HEADER_COMPILE_OPTIONS)
     target_compile_options(${fq_target_name} INTERFACE ${ADD_HEADER_COMPILE_OPTIONS})

libc/config/darwin/arm/headers.txt

@@ -4,6 +4,7 @@ set(TARGET_PUBLIC_HEADERS
     libc.include.fenv
     libc.include.float
     libc.include.inttypes
+    libc.include.limits
     libc.include.math
     libc.include.stdlib
     libc.include.string

libc/config/darwin/x86_64/headers.txt

@@ -5,6 +5,7 @@ set(TARGET_PUBLIC_HEADERS
     #libc.include.fenv
     libc.include.float
     libc.include.inttypes
+    libc.include.limits
     libc.include.math
     libc.include.stdlib
     libc.include.string

libc/config/gpu/headers.txt

@@ -4,6 +4,7 @@ set(TARGET_PUBLIC_HEADERS
     libc.include.string
     libc.include.float
     libc.include.inttypes
+    libc.include.limits
     libc.include.math
     libc.include.fenv
     libc.include.time

libc/config/linux/aarch64/headers.txt

@@ -6,6 +6,7 @@ set(TARGET_PUBLIC_HEADERS
     libc.include.fenv
     libc.include.float
     libc.include.inttypes
+    libc.include.limits
     libc.include.math
     libc.include.pthread
     libc.include.signal

libc/config/linux/riscv/headers.txt

@@ -8,6 +8,7 @@ set(TARGET_PUBLIC_HEADERS
     libc.include.fenv
     libc.include.float
     libc.include.inttypes
+    libc.include.limits
     libc.include.math
     libc.include.pthread
     libc.include.sched

libc/config/linux/x86_64/headers.txt

@@ -8,6 +8,7 @@ set(TARGET_PUBLIC_HEADERS
     libc.include.fenv
     libc.include.float
     libc.include.inttypes
+    libc.include.limits
     libc.include.math
     libc.include.pthread
     libc.include.sched

libc/include/CMakeLists.txt

@@ -83,6 +83,14 @@ add_gen_header(
     .llvm-libc-macros.float_macros
 )
 
+add_gen_header(
+  limits
+  DEF_FILE limits.h.def
+  GEN_HDR limits.h
+  DEPENDS
+    .llvm-libc-macros.limits_macros
+)
+
 add_gen_header(
   math
   DEF_FILE math.h.def

libc/include/limits.h.def

@@ -0,0 +1,14 @@
+//===-- C standard library header limits.h --------------------------------===//
+//
+// 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_LIMITS_H
+#define LLVM_LIBC_LIMITS_H
+
+#include <llvm-libc-macros/limits-macros.h>
+
+#endif // LLVM_LIBC_LIMITS_H

libc/include/llvm-libc-macros/CMakeLists.txt

@@ -73,6 +73,12 @@ add_macro_header(
     float-macros.h
 )
 
+add_macro_header(
+  limits_macros
+  HDR
+    limits-macros.h
+)
+
 add_macro_header(
   math_macros
   HDR