[libc++] Fix header deprecations #163356

philnik777 · 2025-10-14T10:11:17Z

Currently, there are no diagnostics issued when including a deprecated header, since the diagnostic is issued inside a system header. This patch fixes that by using #warning instead, which also simplifies the implementation of the deprecation warnings.

libcxx/test/extensions/clang/clang_modules_include.gen.py

ldionne · 2025-10-23T16:05:13Z

libcxx/test/libcxx/transitive_includes.gen.py


 // RUN: mkdir %t
-// RUN: %{{cxx}} %s %{{flags}} %{{compile_flags}} --trace-includes -fshow-skipped-includes --preprocess > /dev/null 2> %t/trace-includes.txt
+// RUN: %{{cxx}} %s %{{flags}} %{{compile_flags}} -Wno-deprecated --trace-includes -fshow-skipped-includes --preprocess > /dev/null 2> %t/trace-includes.txt


Why were these warnings not showing up before this patch? I think we need to understand that.

libcxx/test/std/depr/depr.cpp.headers/ccomplex.verify.cpp

ldionne · 2025-10-23T16:16:21Z

libcxx/test/std/depr/depr.cpp.headers/ccomplex.verify.cpp


 // UNSUPPORTED: c++03, c++11, c++14
 // UNSUPPORTED: clang-modules-build



If I understand correctly, what's being fixed is that before this patch, this test only passes because we're using -I include/c++/v1 and disabling #pragma system_header. After this patch, this test would now pass if we were using -isystem (which is what end users do). However, we're not actually exercising that as part of this patch. Could we exercise that somehow?

For example, might it make sense to use -isystem for .verify.cpp tests from the Lit configuration? Or not disable #pragma system_header for those tests? We control that from here: https://github.com/llvm/llvm-project/blob/main/libcxx/utils/libcxx/test/params.py#L299

It's quite hacky, but we could perhaps do something like -U_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER when compiling .verify.cpp tests? Not very pretty though.

llvmbot · 2025-10-23T16:17:23Z

@llvm/pr-subscribers-libcxx

Author: Nikolas Klauser (philnik777)

Changes

Currently, there are no diagnostics issued when including a deprecated header, since the diagnostic is issued inside a system header. This patch fixes that by using #warning instead, which also simplifies the implementation of the deprecation warnings.

Full diff: https://github.com/llvm/llvm-project/pull/163356.diff

13 Files Affected:

(modified) libcxx/include/__config (+6)
(modified) libcxx/include/ccomplex (+3-11)
(modified) libcxx/include/ciso646 (+3-6)
(modified) libcxx/include/cstdalign (+3-10)
(modified) libcxx/include/cstdbool (+3-10)
(modified) libcxx/include/ctgmath (+2-11)
(modified) libcxx/test/extensions/clang/clang_modules_include.gen.py (+2-2)
(modified) libcxx/test/libcxx/transitive_includes.gen.py (+1-1)
(modified) libcxx/test/std/depr/depr.cpp.headers/ccomplex.verify.cpp (+1-7)
(modified) libcxx/test/std/depr/depr.cpp.headers/ciso646.verify.cpp (+2-1)
(modified) libcxx/test/std/depr/depr.cpp.headers/cstdalign.verify.cpp (+1-7)
(modified) libcxx/test/std/depr/depr.cpp.headers/cstdbool.verify.cpp (+1-7)
(modified) libcxx/test/std/depr/depr.cpp.headers/ctgmath.verify.cpp (+1-7)

diff --git a/libcxx/include/__config b/libcxx/include/__config
index b4c081dcdff1b..dfc101954bddb 100644
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -721,6 +721,12 @@ typedef __char32_t char32_t;
 #    define _LIBCPP_DEPRECATED_(m)
 #  endif
 
+#  if defined(__DEPRECATED) && __DEPRECATED && !defined(_LIBCPP_DISABLE_DEPRECATION_WARNINGS) && !__building_module(std)
+#    define _LIBCPP_DIAGNOSE_DEPRECATED_HEADERS 1
+#  else
+#    define _LIBCPP_DIAGNOSE_DEPRECATED_HEADERS 0
+#  endif
+
 #  if !defined(_LIBCPP_CXX03_LANG)
 #    define _LIBCPP_DEPRECATED_IN_CXX11 _LIBCPP_DEPRECATED
 #  else
diff --git a/libcxx/include/ccomplex b/libcxx/include/ccomplex
index ee7e088aac54d..bade696b95c70 100644
--- a/libcxx/include/ccomplex
+++ b/libcxx/include/ccomplex
@@ -26,18 +26,10 @@
 #    pragma GCC system_header
 #  endif
 
-#  if _LIBCPP_STD_VER >= 20
-
-using __standard_header_ccomplex
-    _LIBCPP_DEPRECATED_("removed in C++20. Include <complex> instead.") _LIBCPP_NODEBUG = void;
-using __use_standard_header_ccomplex _LIBCPP_NODEBUG                                    = __standard_header_ccomplex;
-
-#  elif _LIBCPP_STD_VER >= 17
-
-using __standard_header_ccomplex _LIBCPP_DEPRECATED_("Include <complex> instead.") _LIBCPP_NODEBUG = void;
-using __use_standard_header_ccomplex _LIBCPP_NODEBUG = __standard_header_ccomplex;
-
+#  if _LIBCPP_STD_VER >= 17 && _LIBCPP_DIAGNOSE_DEPRECATED_HEADERS
+#    warning <ccomplex> is removed in C++20. Include <complex> instead.
 #  endif
+
 #endif // __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS)
 
 #endif // _LIBCPP_CCOMPLEX
diff --git a/libcxx/include/ciso646 b/libcxx/include/ciso646
index 34164362dc10d..f4b1d6fa78ce7 100644
--- a/libcxx/include/ciso646
+++ b/libcxx/include/ciso646
@@ -24,13 +24,10 @@
 #    pragma GCC system_header
 #  endif
 
-#  if _LIBCPP_STD_VER >= 20
-
-using __standard_header_ciso646
-    _LIBCPP_DEPRECATED_("removed in C++20. Include <version> instead.") _LIBCPP_NODEBUG = void;
-using __use_standard_header_ciso646 _LIBCPP_NODEBUG                                     = __standard_header_ciso646;
-
+#  if _LIBCPP_STD_VER >= 20 && _LIBCPP_DIAGNOSE_DEPRECATED_HEADERS
+#    warning <ciso646> is removed in C++20. Include <version> instead.
 #  endif
+
 #endif // __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS)
 
 #endif // _LIBCPP_CISO646
diff --git a/libcxx/include/cstdalign b/libcxx/include/cstdalign
index 7f8dd1e1fbaf8..60b2963c10fb4 100644
--- a/libcxx/include/cstdalign
+++ b/libcxx/include/cstdalign
@@ -43,17 +43,10 @@ Macros:
 #  undef __alignof_is_defined
 #  define __alignof_is_defined 1
 
-#  if _LIBCPP_STD_VER >= 20
-
-using __standard_header_cstdalign _LIBCPP_DEPRECATED_("removed in C++20.") _LIBCPP_NODEBUG = void;
-using __use_standard_header_cstdalign _LIBCPP_NODEBUG = __standard_header_cstdalign;
-
-#  elif _LIBCPP_STD_VER >= 17
-
-using __standard_header_cstdalign _LIBCPP_DEPRECATED _LIBCPP_NODEBUG = void;
-using __use_standard_header_cstdalign _LIBCPP_NODEBUG                = __standard_header_cstdalign;
-
+#  if _LIBCPP_STD_VER >= 17 && _LIBCPP_DIAGNOSE_DEPRECATED_HEADERS
+#    warning <cstdalign> is removed in C++20.
 #  endif
+
 #endif // __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS)
 
 #endif // _LIBCPP_CSTDALIGN
diff --git a/libcxx/include/cstdbool b/libcxx/include/cstdbool
index a432d5f08b9ae..78b98699460dc 100644
--- a/libcxx/include/cstdbool
+++ b/libcxx/include/cstdbool
@@ -31,17 +31,10 @@ Macros:
 #  undef __bool_true_false_are_defined
 #  define __bool_true_false_are_defined 1
 
-#  if _LIBCPP_STD_VER >= 20
-
-using __standard_header_cstdbool _LIBCPP_DEPRECATED_("removed in C++20.") _LIBCPP_NODEBUG = void;
-using __use_standard_header_cstdbool _LIBCPP_NODEBUG                                      = __standard_header_cstdbool;
-
-#  elif _LIBCPP_STD_VER >= 17
-
-using __standard_header_cstdbool _LIBCPP_DEPRECATED _LIBCPP_NODEBUG = void;
-using __use_standard_header_cstdbool _LIBCPP_NODEBUG                = __standard_header_cstdbool;
-
+#  if _LIBCPP_STD_VER >= 17 && _LIBCPP_DIAGNOSE_DEPRECATED_HEADERS
+#    warning <cstdbool> is removed in C++20.
 #  endif
+
 #endif // __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS)
 
 #endif // _LIBCPP_CSTDBOOL
diff --git a/libcxx/include/ctgmath b/libcxx/include/ctgmath
index db0786f1e2c46..9a0049a38880f 100644
--- a/libcxx/include/ctgmath
+++ b/libcxx/include/ctgmath
@@ -28,17 +28,8 @@
 #    pragma GCC system_header
 #  endif
 
-#  if _LIBCPP_STD_VER >= 20
-
-using __standard_header_ctgmath
-    _LIBCPP_DEPRECATED_("removed in C++20. Include <cmath> and <complex> instead.") _LIBCPP_NODEBUG = void;
-using __use_standard_header_ctgmath _LIBCPP_NODEBUG = __standard_header_ctgmath;
-
-#  elif _LIBCPP_STD_VER >= 17
-
-using __standard_header_ctgmath _LIBCPP_DEPRECATED_("Include <cmath> and <complex> instead.") _LIBCPP_NODEBUG = void;
-using __use_standard_header_ctgmath _LIBCPP_NODEBUG = __standard_header_ctgmath;
-
+#  if _LIBCPP_STD_VER >= 17 && _LIBCPP_DIAGNOSE_DEPRECATED_HEADERS
+#    warning <ctgmath> is removed in C++20. Include <cmath> and <complex> instead.
 #  endif
 
 #endif // __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS)
diff --git a/libcxx/test/extensions/clang/clang_modules_include.gen.py b/libcxx/test/extensions/clang/clang_modules_include.gen.py
index 28661049d6e85..f21c2cc9fd805 100644
--- a/libcxx/test/extensions/clang/clang_modules_include.gen.py
+++ b/libcxx/test/extensions/clang/clang_modules_include.gen.py
@@ -50,7 +50,7 @@
     print(
         f"""\
 //--- {header}.compile.pass.cpp
-// RUN: %{{cxx}} %s %{{flags}} %{{compile_flags}} -fmodules -fcxx-modules -fmodules-cache-path=%t -fsyntax-only
+// RUN: %{{cxx}} %s %{{flags}} %{{compile_flags}} -fmodules -fcxx-modules -fmodules-cache-path=%t -fsyntax-only -Wno-deprecated
 
 {lit_header_restrictions.get(header, '')}
 {lit_header_undeprecations.get(header, '')}
@@ -62,7 +62,7 @@
 print(
     f"""\
 //--- import_std.compile.pass.mm
-// RUN: %{{cxx}} %s %{{flags}} %{{compile_flags}} -fmodules -fcxx-modules -fmodules-cache-path=%t -fsyntax-only
+// RUN: %{{cxx}} %s %{{flags}} %{{compile_flags}} -fmodules -fcxx-modules -fmodules-cache-path=%t -fsyntax-only -Wno-deprecated
 
 // REQUIRES: clang-modules-build
 
diff --git a/libcxx/test/libcxx/transitive_includes.gen.py b/libcxx/test/libcxx/transitive_includes.gen.py
index 6ed35af7e275e..2b643e1f2ad48 100644
--- a/libcxx/test/libcxx/transitive_includes.gen.py
+++ b/libcxx/test/libcxx/transitive_includes.gen.py
@@ -89,7 +89,7 @@
 // UNSUPPORTED: LIBCXX-FREEBSD-FIXME
 
 // RUN: mkdir %t
-// RUN: %{{cxx}} %s %{{flags}} %{{compile_flags}} --trace-includes -fshow-skipped-includes --preprocess > /dev/null 2> %t/trace-includes.txt
+// RUN: %{{cxx}} %s %{{flags}} %{{compile_flags}} -Wno-deprecated --trace-includes -fshow-skipped-includes --preprocess > /dev/null 2> %t/trace-includes.txt
 // RUN: %{{python}} %{{libcxx-dir}}/test/libcxx/transitive_includes/to_csv.py %t/trace-includes.txt > %t/actual_transitive_includes.csv
 // RUN: cat %{{libcxx-dir}}/test/libcxx/transitive_includes/%{{cxx_std}}.csv | awk '/^{escaped_header} / {{ print }}' > %t/expected_transitive_includes.csv
 // RUN: diff -w %t/expected_transitive_includes.csv %t/actual_transitive_includes.csv
diff --git a/libcxx/test/std/depr/depr.cpp.headers/ccomplex.verify.cpp b/libcxx/test/std/depr/depr.cpp.headers/ccomplex.verify.cpp
index 0eaf82ce5cef0..f63c971f9592f 100644
--- a/libcxx/test/std/depr/depr.cpp.headers/ccomplex.verify.cpp
+++ b/libcxx/test/std/depr/depr.cpp.headers/ccomplex.verify.cpp
@@ -14,12 +14,6 @@
 // UNSUPPORTED: c++03, c++11, c++14
 // UNSUPPORTED: clang-modules-build
 
-#include "test_macros.h"
-
 #include <ccomplex>
 
-#if TEST_STD_VER >= 20
-// expected-warning@ccomplex:* {{'__standard_header_ccomplex' is deprecated: removed in C++20. Include <complex> instead.}}
-#else
-// expected-warning@ccomplex:* {{'__standard_header_ccomplex' is deprecated: Include <complex> instead.}}
-#endif
+// expected-warning@ccomplex:* {{<ccomplex> is removed in C++20. Include <complex> instead.}}
diff --git a/libcxx/test/std/depr/depr.cpp.headers/ciso646.verify.cpp b/libcxx/test/std/depr/depr.cpp.headers/ciso646.verify.cpp
index 04acd10081548..32b57033331c8 100644
--- a/libcxx/test/std/depr/depr.cpp.headers/ciso646.verify.cpp
+++ b/libcxx/test/std/depr/depr.cpp.headers/ciso646.verify.cpp
@@ -15,4 +15,5 @@
 // UNSUPPORTED: clang-modules-build
 
 #include <ciso646>
-// expected-warning@ciso646:* {{'__standard_header_ciso646' is deprecated: removed in C++20. Include <version> instead.}}
+
+// expected-warning@ciso646:* {{<ciso646> is removed in C++20. Include <version> instead.}}
diff --git a/libcxx/test/std/depr/depr.cpp.headers/cstdalign.verify.cpp b/libcxx/test/std/depr/depr.cpp.headers/cstdalign.verify.cpp
index dc9f1af55b3f1..258e82cfe0ad2 100644
--- a/libcxx/test/std/depr/depr.cpp.headers/cstdalign.verify.cpp
+++ b/libcxx/test/std/depr/depr.cpp.headers/cstdalign.verify.cpp
@@ -14,12 +14,6 @@
 // UNSUPPORTED: c++03, c++11, c++14
 // UNSUPPORTED: clang-modules-build
 
-#include "test_macros.h"
-
 #include <cstdalign>
 
-#if TEST_STD_VER >= 20
-// expected-warning@cstdalign:* {{'__standard_header_cstdalign' is deprecated: removed in C++20.}}
-#else
-// expected-warning@cstdalign:* {{'__standard_header_cstdalign' is deprecated}}
-#endif
+// expected-warning@cstdalign:* {{<cstdalign> is removed in C++20.}}
diff --git a/libcxx/test/std/depr/depr.cpp.headers/cstdbool.verify.cpp b/libcxx/test/std/depr/depr.cpp.headers/cstdbool.verify.cpp
index eddefe14d35ea..5c89cfad27c3d 100644
--- a/libcxx/test/std/depr/depr.cpp.headers/cstdbool.verify.cpp
+++ b/libcxx/test/std/depr/depr.cpp.headers/cstdbool.verify.cpp
@@ -14,12 +14,6 @@
 // UNSUPPORTED: c++03, c++11, c++14
 // UNSUPPORTED: clang-modules-build
 
-#include "test_macros.h"
-
 #include <cstdbool>
 
-#if TEST_STD_VER >= 20
-// expected-warning@cstdbool:* {{'__standard_header_cstdbool' is deprecated: removed in C++20.}}
-#else
-// expected-warning@cstdbool:* {{'__standard_header_cstdbool' is deprecated}}
-#endif
+// expected-warning@cstdbool:* {{<cstdbool> is removed in C++20.}}
diff --git a/libcxx/test/std/depr/depr.cpp.headers/ctgmath.verify.cpp b/libcxx/test/std/depr/depr.cpp.headers/ctgmath.verify.cpp
index 097ab1643d15a..1ada3768f894d 100644
--- a/libcxx/test/std/depr/depr.cpp.headers/ctgmath.verify.cpp
+++ b/libcxx/test/std/depr/depr.cpp.headers/ctgmath.verify.cpp
@@ -14,12 +14,6 @@
 // UNSUPPORTED: c++03, c++11, c++14
 // UNSUPPORTED: clang-modules-build
 
-#include "test_macros.h"
-
 #include <ctgmath>
 
-#if TEST_STD_VER >= 20
-// expected-warning@ctgmath:* {{'__standard_header_ctgmath' is deprecated: removed in C++20. Include <cmath> and <complex> instead.}}
-#else
-// expected-warning@ctgmath:* {{'__standard_header_ctgmath' is deprecated: Include <cmath> and <complex> instead.}}
-#endif
+// expected-warning@ctgmath:* {{<ctgmath> is removed in C++20. Include <cmath> and <complex> instead.}}

philnik777 force-pushed the simplify_header_deprecations branch 2 times, most recently from 3f18fc7 to 1d5093e Compare October 14, 2025 11:30

philnik777 changed the title ~~[libc++] Simplify how headers are deprecated~~ [libc++] Fix header deprecations Oct 15, 2025

philnik777 force-pushed the simplify_header_deprecations branch 2 times, most recently from 3861df3 to ddaebf4 Compare October 17, 2025 12:36

ldionne requested changes Oct 23, 2025

View reviewed changes

ldionne marked this pull request as ready for review October 23, 2025 16:16

ldionne requested a review from a team as a code owner October 23, 2025 16:16

llvmbot added the libc++ libc++ C++ Standard Library. Not GNU libstdc++. Not libc++abi. label Oct 23, 2025

philnik777 force-pushed the simplify_header_deprecations branch from ddaebf4 to a83b41f Compare October 24, 2025 09:47

[libc++] Simplify how headers are deprecated

b1d3271

philnik777 force-pushed the simplify_header_deprecations branch from a83b41f to b1d3271 Compare October 27, 2025 16:04

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[libc++] Fix header deprecations #163356

[libc++] Fix header deprecations #163356

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		// UNSUPPORTED: c++03, c++11, c++14
		// UNSUPPORTED: clang-modules-build

[libc++] Fix header deprecations #163356

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[libc++] Fix header deprecations #163356

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