Hi!
On 2025-04-29T21:09:17+0100, Jonathan Wakely <jwak...@redhat.com> wrote:
> The GLIBCXX_ENABLE_BACKTRACE macro currently uses the
> glibcxx_ac_atomic_int macro defined by the checks that this commit
> removes from GLIBCXX_ENABLE_ATOMIC_BUILTINS. That wasn't a good check
> anyway, because libbacktrace actually depends on atomic loads+stores for
> pointers as well as int, and for atomic stores for size_t. This commit
> replaces the glibcxx_ac_atomic_int check with a proper test for all the
> required atomic operations on all three of int, void* and size_t. This
> ensures that the libbacktrace code used for std::stacktrace will either
> use native atomics, or implement those loads and stores only in terms of
> __sync_bool_compare_and_swap (possibly requiring that to come from
> libatomic or elsewhere).
> Tested x86_64-linux, no changes to the c++config.h results.
> I need to do more testing on other targets.
Hmm... ;-P
Pushed to trunk branch commit 4589ccbed5cad42296d4d1810b61e8dec0dadf79
"libstdc++: Rewrite atomic builtin checks: Fix up 'GLIBCXX_ENABLE_BACKTRACE'
check with 'size_t' [PR119667]",
see attached.
Grüße
Thomas
>From 4589ccbed5cad42296d4d1810b61e8dec0dadf79 Mon Sep 17 00:00:00 2001
From: Thomas Schwinge <tschwi...@baylibre.com>
Date: Mon, 12 May 2025 10:35:11 +0200
Subject: [PATCH] libstdc++: Rewrite atomic builtin checks: Fix up
'GLIBCXX_ENABLE_BACKTRACE' check with 'size_t' [PR119667]
Fix-up for commit 86627faec10da53d7532805019e5296fcf15ac09
"libstdc++: Rewrite atomic builtin checks [PR70560]", which, for example, for
x86_64-pc-linux-gnu lost '-DHAVE_ATOMIC_FUNCTIONS=1' from 'BACKTRACE_CPPFLAGS'
due to:
configure:53554: checking for atomic builtins for libbacktrace
configure:53587: [...]/./gcc/xgcc -shared-libgcc -B[...]/./gcc -nostdinc++ -L[...]/x86_64-pc-linux-gnu/libstdc++-v3/src -L[...]/x86_64-pc-linux-gnu/libstdc++-v3/src/.libs -L[...]/x86_64-pc-linux-gnu/libstdc++-v3/libsupc++/.libs -B/x86_64-pc-linux-gnu/bin/ -B/x86_64-pc-linux-gnu/lib/ -isystem /x86_64-pc-linux-gnu/include -isystem /x86_64-pc-linux-gnu/sys-include -o conftest -O0 conftest.cpp >&5
conftest.cpp: In function 'int main()':
conftest.cpp:265:13: error: 'size_t' was not declared in this scope
265 | size_t s = 0;
| ^~~~~~
conftest.cpp:1:1: note: 'size_t' is defined in header '<cstddef>'; this is probably fixable by adding '#include <cstddef>'
1 | /* confdefs.h */
conftest.cpp:273:31: error: 's' was not declared in this scope
273 | __atomic_store_n(&s, s, __ATOMIC_RELEASE);
| ^
configure:53587: $? = 1
configure: failed program was:
| /* confdefs.h */
[...]
| int
| main ()
| {
|[...]
| size_t s = 0;
|[...]
| // backtrace_atomic_store_size_t
| __atomic_store_n(&s, s, __ATOMIC_RELEASE);
|[...]
| }
configure:53595: result: no
PR libstdc++/70560
PR libstdc++/119667
libstdc++-v3/
* acinclude.m4 (GLIBCXX_ENABLE_BACKTRACE): Use '__SIZE_TYPE__'
instead of 'size_t'.
* configure: Regenerate.
---
libstdc++-v3/acinclude.m4 | 4 ++--
libstdc++-v3/configure | 4 ++--
2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index 204bed5b27b..d1ecb1ad956 100644
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -5304,7 +5304,7 @@ AC_DEFUN([GLIBCXX_ENABLE_BACKTRACE], [
[AC_TRY_LINK([], [
int i = 0;
int* p = &i;
- size_t s = 0;
+ __SIZE_TYPE__ s = 0;
// backtrace_atomic_load_pointer
void* vp = __atomic_load_n(&p, __ATOMIC_ACQUIRE);
// backtrace_atomic_load_int
@@ -5331,7 +5331,7 @@ int main()
{
int i = 0;
int* p = &i;
- size_t s = 0;
+ __SIZE_TYPE__ s = 0;
// backtrace_atomic_load_pointer
void* vp = __atomic_load_n(&p, __ATOMIC_ACQUIRE);
// backtrace_atomic_load_int
diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure
index 0529ff5708f..d6891e544cf 100755
--- a/libstdc++-v3/configure
+++ b/libstdc++-v3/configure
@@ -53568,7 +53568,7 @@ main ()
int i = 0;
int* p = &i;
- size_t s = 0;
+ __SIZE_TYPE__ s = 0;
// backtrace_atomic_load_pointer
void* vp = __atomic_load_n(&p, __ATOMIC_ACQUIRE);
// backtrace_atomic_load_int
@@ -53607,7 +53607,7 @@ int main()
{
int i = 0;
int* p = &i;
- size_t s = 0;
+ __SIZE_TYPE__ s = 0;
// backtrace_atomic_load_pointer
void* vp = __atomic_load_n(&p, __ATOMIC_ACQUIRE);
// backtrace_atomic_load_int
--
2.34.1
