From d4c57dcc71e70f24e3a0cd1af3c4bd4524a14ac5 Mon Sep 17 00:00:00 2001
From: Victor Stinner <vstinner@python.org>
Date: Thu, 12 Mar 2026 23:48:51 +0100
Subject: [PATCH] gh-145801: Use gcc -fprofile-update=atomic for PGO builds
 (#145802)

When Python build is optimized with GCC using PGO, use
-fprofile-update=atomic option to use atomic operations when updating
profile information. This option reduces the risk of gcov Data Files
(.gcda) corruption which can cause random GCC crashes.

(cherry picked from commit 08a018ebe0d673e9c352f790d2e4604d69604188)
---
 ...-03-11-11-58-42.gh-issue-145801.iCXa3v.rst |  4 ++
 configure                                     | 39 ++++++++++++++++++-
 configure.ac                                  |  5 ++-
 3 files changed, 46 insertions(+), 2 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Build/2026-03-11-11-58-42.gh-issue-145801.iCXa3v.rst

diff --git a/Misc/NEWS.d/next/Build/2026-03-11-11-58-42.gh-issue-145801.iCXa3v.rst b/Misc/NEWS.d/next/Build/2026-03-11-11-58-42.gh-issue-145801.iCXa3v.rst
new file mode 100644
index 00000000000000..c5f3982cc5416c
--- /dev/null
+++ b/Misc/NEWS.d/next/Build/2026-03-11-11-58-42.gh-issue-145801.iCXa3v.rst
@@ -0,0 +1,4 @@
+When Python build is optimized with GCC using PGO, use
+``-fprofile-update=atomic`` option to use atomic operations when updating
+profile information. This option reduces the risk of gcov Data Files (.gcda)
+corruption which can cause random GCC crashes. Patch by Victor Stinner.
diff --git a/configure b/configure
index 49b6795703ac68..9ddb712b5344d4 100755
--- a/configure
+++ b/configure
@@ -8990,7 +8990,44 @@ case "$CC_BASENAME" in
         fi
         ;;
       *)
-        PGO_PROF_GEN_FLAG="-fprofile-generate"
+        { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether C compiler accepts -fprofile-update=atomic" >&5
+printf %s "checking whether C compiler accepts -fprofile-update=atomic... " >&6; }
+if test ${ax_cv_check_cflags___fprofile_update_atomic+y}
+then :
+  printf %s "(cached) " >&6
+else $as_nop
+
+  ax_check_save_flags=$CFLAGS
+  CFLAGS="$CFLAGS  -fprofile-update=atomic"
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main (void)
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"
+then :
+  ax_cv_check_cflags___fprofile_update_atomic=yes
+else $as_nop
+  ax_cv_check_cflags___fprofile_update_atomic=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext
+  CFLAGS=$ax_check_save_flags
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ax_cv_check_cflags___fprofile_update_atomic" >&5
+printf "%s\n" "$ax_cv_check_cflags___fprofile_update_atomic" >&6; }
+if test "x$ax_cv_check_cflags___fprofile_update_atomic" = xyes
+then :
+  PGO_PROF_GEN_FLAG="-fprofile-generate -fprofile-update=atomic"
+else $as_nop
+  PGO_PROF_GEN_FLAG="-fprofile-generate"
+fi
+
         PGO_PROF_USE_FLAG="-fprofile-use -fprofile-correction"
         LLVM_PROF_MERGER="true"
         LLVM_PROF_FILE=""
diff --git a/configure.ac b/configure.ac
index 94776540d1b373..d9acfce793e533 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2137,7 +2137,10 @@ case "$CC_BASENAME" in
         fi
         ;;
       *)
-        PGO_PROF_GEN_FLAG="-fprofile-generate"
+        AX_CHECK_COMPILE_FLAG(
+            [-fprofile-update=atomic],
+            [PGO_PROF_GEN_FLAG="-fprofile-generate -fprofile-update=atomic"],
+            [PGO_PROF_GEN_FLAG="-fprofile-generate"])
         PGO_PROF_USE_FLAG="-fprofile-use -fprofile-correction"
         LLVM_PROF_MERGER="true"
         LLVM_PROF_FILE=""