From: Paul Eggert <eggert@cs.ucla.edu>
Date: Sat, 3 Jun 2023 05:30:52 +0000 (-0700)
Subject: error: do not evaluate status twice
X-Git-Tag: v1.0~1261
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=cfd41b3ac199a4f95fb78ee251e8c8a7c6f86ad1;p=thirdparty%2Fgnulib.git

error: do not evaluate status twice

Do this in a different way, so that the status is evaluated
once even when not optimizing and when using GCC.
* lib/error.in.h (__gl_error_call1) [__GNUC__]: New macro.
(__gl_error_call) [__GNUC__]: Use it.
---

diff --git a/ChangeLog b/ChangeLog
index 3187128c1f..fda2ed0e3f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2023-06-02  Paul Eggert  <eggert@cs.ucla.edu>
+
+	error: do not evaluate status twice
+	Do this in a different way, so that the status is evaluated
+	once even when not optimizing and when using GCC.
+	* lib/error.in.h (__gl_error_call1) [__GNUC__]: New macro.
+	(__gl_error_call) [__GNUC__]: Use it.
+
 2023-06-02  Bruno Haible  <bruno@clisp.org>
 
 	warnings: Add ability to inhibit all warnings.
diff --git a/lib/error.in.h b/lib/error.in.h
index f37dba170c..279258f63e 100644
--- a/lib/error.in.h
+++ b/lib/error.in.h
@@ -50,23 +50,20 @@
 #endif
 
 /* Helper macro for supporting the compiler's control flow analysis better.
+   It evaluates its arguments only once.  It uses __builtin_constant_p
+   and comma expressions to work around GCC false positives.
    Test case: Compile copy-file.c with "gcc -Wimplicit-fallthrough".  */
 #ifdef __GNUC__
-/* Avoid evaluating STATUS twice, if this is possible without making the
-   "warning: this statement may fall through" reappear.  */
-# if __OPTIMIZE__
-#  define __gl_error_call(function, status, ...) \
-     ({ \
-        int const __errstatus = (status); \
-        (function) (__errstatus, __VA_ARGS__); \
-        __errstatus != 0 ? unreachable () : (void) 0; \
-     })
-# else
-#  define __gl_error_call(function, status, ...) \
-     ((function) (status, __VA_ARGS__), \
-      (status) != 0 ? unreachable () : (void)0 \
-     )
-# endif
+# define __gl_error_call1(function, status, ...) \
+    ((function) (status, __VA_ARGS__), \
+     (status) != 0 ? unreachable () : (void) 0)
+# define __gl_error_call(function, status, ...) \
+    (__builtin_constant_p (status) \
+     ? __gl_error_call1 (function, status, __VA_ARGS__) \
+     : ({ \
+         int const __errstatus = status; \
+         __gl_error_call1 (function, __errstatus, __VA_ARGS__); \
+       }))
 #else
 # define __gl_error_call(function, status, ...) \
     (function) (status, __VA_ARGS__)