[3.12] gh-123917: Fix crypt check in configure (#123952)

Use a global volatile variable and check if the function is not NULL to use the variable. Otherwise, a compiler optimization can remove the variable making the check useless. Co-authored-by: Paul Smith <[email protected]>
python · Sep 12, 2024 · 53af5b2 · 53af5b2
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diff --git a/Misc/NEWS.d/next/Build/2024-09-11-16-06-42.gh-issue-123917.JuZl0r.rst b/Misc/NEWS.d/next/Build/2024-09-11-16-06-42.gh-issue-123917.JuZl0r.rst
@@ -0,0 +1,2 @@
+Fix the check for the ``crypt()`` function in the configure script. Patch by
+Paul Smith and Victor Stinner.
diff --git a/configure b/configure
diff --git a/configure.ac b/configure.ac
@@ -5237,12 +5237,14 @@ WITH_SAVE_ENV([
           #include <crypt.h>
         #endif
         #include <unistd.h>
+        volatile void *func;
       ], [
         #ifdef HAVE_CRYPT_R
-          void *x = crypt_r;
+          func = crypt_r;
         #else
-          void *x = crypt;
+          func = crypt;
         #endif
+          return (func != NULL);
       ])
     ], [ac_cv_crypt_crypt=yes], [ac_cv_crypt_crypt=no])
   ])
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		Fix the check for the ``crypt()`` function in the configure script. Patch by
		Paul Smith and Victor Stinner.