Enable frame pointers by default for CPython builds

Author: pablogsal

Doc/howto/perf_profiling.rst

@@ -217,8 +217,9 @@ Example, using the :mod:`sys` APIs in file :file:`example.py`:
 How to obtain the best results
 ------------------------------
 
-For best results, Python should be compiled with
-``CFLAGS="-fno-omit-frame-pointer -mno-omit-leaf-frame-pointer"`` as this allows
+For best results, keep frame pointers enabled. On supported GCC-compatible
+toolchains, CPython builds itself with ``-fno-omit-frame-pointer`` and, when
+available, ``-mno-omit-leaf-frame-pointer`` by default. These flags allow
 profilers to unwind using only the frame pointer and not on DWARF debug
 information. This is because as the code that is interposed to allow ``perf``
 support is dynamically generated it doesn't have any DWARF debugging information

Lib/test/test_frame_pointer_unwind.py

@@ -27,9 +27,8 @@ def _frame_pointers_expected(machine):
     )
 
     if "no-omit-frame-pointer" in cflags:
-        # For example, configure adds -fno-omit-frame-pointer if Python
-        # has perf trampoline (PY_HAVE_PERF_TRAMPOLINE) and Python is built
-        # in debug mode.
+        # For example, configure adds -fno-omit-frame-pointer by default on
+        # supported GCC-compatible builds.
         return True
     if "omit-frame-pointer" in cflags:
         return False

Misc/NEWS.d/next/Core_and_Builtins/2026-04-05-16-10-00.gh-issue-149202.W8sQeR.rst

@@ -0,0 +1,3 @@
+Enable frame pointers by default for GCC-compatible CPython builds, including
+``-mno-omit-leaf-frame-pointer`` when the compiler supports it, so profilers
+and debuggers can unwind native interpreter frames more reliably.

configure

@@ -2490,6 +2490,19 @@ then
 fi
 
 AS_VAR_IF([ac_cv_gcc_compat], [yes], [
+    dnl Keep frame pointers in CPython and stdlib objects so native profilers
+    dnl can unwind interpreter frames and generated trampolines without DWARF.
+    frame_pointer_cflags=
+    AX_CHECK_COMPILE_FLAG([-fno-omit-frame-pointer], [
+      frame_pointer_cflags="-fno-omit-frame-pointer"
+      AX_CHECK_COMPILE_FLAG([-mno-omit-leaf-frame-pointer], [
+        frame_pointer_cflags="$frame_pointer_cflags -mno-omit-leaf-frame-pointer"
+      ], [], [-Werror])
+    ], [], [-Werror])
+    if test -n "$frame_pointer_cflags"; then
+      CFLAGS_NODIST="$frame_pointer_cflags $CFLAGS_NODIST"
+    fi
+
     CFLAGS_NODIST="$CFLAGS_NODIST -std=c11"
 
     PY_CHECK_CC_WARNING([enable], [extra], [if we can add -Wextra])
@@ -3748,11 +3761,6 @@ AC_MSG_RESULT([$perf_trampoline])
 AS_VAR_IF([perf_trampoline], [yes], [
   AC_DEFINE([PY_HAVE_PERF_TRAMPOLINE], [1], [Define to 1 if you have the perf trampoline.])
   PERF_TRAMPOLINE_OBJ=Python/asm_trampoline.o
-
-  dnl perf needs frame pointers for unwinding, include compiler option in debug builds
-  AS_VAR_IF([Py_DEBUG], [true], [
-    AS_VAR_APPEND([BASECFLAGS], [" -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer"])
-  ])
 ])
 AC_SUBST([PERF_TRAMPOLINE_OBJ])