gh-131093: Enforce -std=c11 for gcc at configure time rather than make time

CS-cwhite · CS-cwhite · commit bc5c9ed7336f · 2025-05-12T11:25:12.000-04:00
When compiling under gcc, configure.ac currently assumes -std=c11 rather
than checking it.  This causes configure to succeed but make to fail on
old compilers.  Fix this by adding a check for -std=c11 in configure.ac.
diff --git a/Misc/ACKS b/Misc/ACKS
@@ -2032,6 +2032,7 @@ Cliff Wells
 Rickard Westman
 Joseph Weston
 Jeff Wheeler
+Chris White
 Christopher White
 David White
 Mats Wichmann
diff --git a/Misc/NEWS.d/next/Build/2025-03-13-13-43-51.gh-issue-131093.q2jF6K.rst b/Misc/NEWS.d/next/Build/2025-03-13-13-43-51.gh-issue-131093.q2jF6K.rst
@@ -0,0 +1,3 @@
+On GCC-compatible compilers, check at configure time that ``-std=c11``
+works. This way you don't hit an "invalid option" error at make time on old
+compilers.
diff --git a/configure b/configure
diff --git a/configure.ac b/configure.ac
@@ -2456,7 +2456,11 @@ then
 fi
 
 AS_VAR_IF([ac_cv_gcc_compat], [yes], [
-    CFLAGS_NODIST="$CFLAGS_NODIST -std=c11"
+    AX_CHECK_COMPILE_FLAG([-std=c11],[
+      AS_VAR_APPEND([CFLAGS_NODIST], [" -std=c11"])
+    ], [
+      AC_MSG_ERROR([Python requires -std=c11 on gcc])
+    ], [-Werror])
 
     PY_CHECK_CC_WARNING([enable], [extra], [if we can add -Wextra])
     AS_VAR_IF([ac_cv_enable_extra_warning], [yes],

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	+On GCC-compatible compilers, check at configure time that ``-std=c11``
	`2`	`+works. This way you don't hit an "invalid option" error at make time on old`
	`3`	`+compilers.`