gh-145801: Use gcc -fprofile-update=atomic for PGO builds

vstinner · vstinner · commit dfb0a1a7f164 · 2026-03-11T12:03:01.000+01:00
When Python build is optimized by PGO, use GCC
-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.
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
@@ -0,0 +1,4 @@
+When Python build is optimized by PGO, use GCC ``-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
diff --git a/configure.ac b/configure.ac
@@ -2084,7 +2084,7 @@ case "$ac_cv_cc_name" in
     fi
     ;;
   gcc)
-    PGO_PROF_GEN_FLAG="-fprofile-generate"
+    PGO_PROF_GEN_FLAG="-fprofile-generate -fprofile-update=atomic"
     PGO_PROF_USE_FLAG="-fprofile-use -fprofile-correction"
     LLVM_PROF_MERGER="true"
     LLVM_PROF_FILE=""
