From fdac511bb5adc241e03042247a0037e9a8437bd3 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
 (GH-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)

Co-authored-by: Victor Stinner <vstinner@python.org>
---
 ...-03-11-11-58-42.gh-issue-145801.iCXa3v.rst |  4 ++
 configure                                     | 42 ++++++++++++++++++-
 configure.ac                                  |  5 ++-
 3 files changed, 49 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 60a88b29b538da..3e507be82c046a 100755
--- a/configure
+++ b/configure
@@ -9049,7 +9049,47 @@ case "$ac_cv_cc_name" in
     fi
     ;;
   gcc)
-    PGO_PROF_GEN_FLAG="-fprofile-generate"
+    { printf "%s\n" "$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 ${ax_cv_check_cflags___fprofile_update_atomic+y}
+then :
+  printf %s "(cached) " >&6
+else case e in #(
+  e)
+  ax_check_save_flags=$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 "$LINENO"
+then :
+  ax_cv_check_cflags___fprofile_update_atomic=yes
+else case e in #(
+  e) ax_cv_check_cflags___fprofile_update_atomic=no ;;
+esac
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext
+  CFLAGS=$ax_check_save_flags ;;
+esac
+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$ax_cv_check_cflags___fprofile_update_atomic" = xyes
+then :
+  PGO_PROF_GEN_FLAG="-fprofile-generate -fprofile-update=atomic"
+else case e in #(
+  e) PGO_PROF_GEN_FLAG="-fprofile-generate" ;;
+esac
+fi
+
     PGO_PROF_USE_FLAG="-fprofile-use -fprofile-correction"
     LLVM_PROF_MERGER="true"
     LLVM_PROF_FILE=""
diff --git a/configure.ac b/configure.ac
index ec93a743817268..a1f4a5670957be 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2072,7 +2072,10 @@ case "$ac_cv_cc_name" in
     fi
     ;;
   gcc)
-    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=""