On 08/05/2026 14:08, Bruno Haible wrote:
Pádraig Brady wrote:
As of gnulib commit 4a127339b244
coreutils CI is failing on GCC 10 with:
CC src/coreutils-coreutils.o
cc1: error: command-line option '-Wuseless-cast' is valid for C++/ObjC++ but
not for C [-Werror]
cc1: all warnings being treated as errors
I can reproduce it by configuring coreutils with
./configure --enable-gcc-warnings
with gcc 13.
The config.log contains this:
configure:97102: checking whether C compiler handles -Wuseless-cast
configure:97122: gcc -o conftest -g -O2 -Wuseless-cast conftest.c >&5
cc1: warning: command-line option '-Wuseless-cast' is valid for C++/ObjC++ but
not for C
configure:97122: $? = 0
configure:97136: result: yes
It looks like manywarnings.m4 should only try this option if the gcc version
is >= 14.
Ah right.
Since GCC 14 was only released 2 years ago,
I've pushed the attached to avoid this issue on older compilers.
I verified it avoids the issue on GCC 10.
thanks!
Padraig
From b933a2ef8648bdac1f60fbc3cfbf285858344a93 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C3=A1draig=20Brady?= <[email protected]>
Date: Fri, 8 May 2026 15:17:53 +0100
Subject: [PATCH] manywarnings: avoid -Wuseless-cast warnings on GCC <= 13
* m4/manywarnings.m4: Only consider -Wuseless-cast on GCC >= 14
Fix suggested by Bruno Haible.
---
ChangeLog | 6 ++++++
m4/manywarnings.m4 | 12 ++++++++++--
2 files changed, 16 insertions(+), 2 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index d1a36a44ab..cf9294505c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2026-05-08 Pádraig Brady <[email protected]>
+
+ manywarnings: avoid -Wuseless-cast warnings on GCC <= 13
+ * m4/manywarnings.m4: Only consider -Wuseless-cast on GCC >= 14
+ Fix suggested by Bruno Haible.
+
2026-05-08 Bruno Haible <[email protected]>
Revisit some -Wuseless-cast changes.
diff --git a/m4/manywarnings.m4 b/m4/manywarnings.m4
index fe382e93e4..6e08abd68f 100644
--- a/m4/manywarnings.m4
+++ b/m4/manywarnings.m4
@@ -1,5 +1,5 @@
# manywarnings.m4
-# serial 34
+# serial 35
dnl Copyright (C) 2008-2026 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
@@ -147,7 +147,6 @@ AC_DEFUN([gl_MANYWARN_ALL_GCC(C)],
-Wunknown-pragmas \
-Wunsafe-loop-optimizations \
-Wunused-macros \
- -Wuseless-cast \
-Wvariadic-macros \
-Wvector-operation-performance \
-Wvla \
@@ -184,6 +183,15 @@ AC_DEFUN([gl_MANYWARN_ALL_GCC(C)],
AS_VAR_APPEND([$1], [' -fno-common'])
;;
esac
+ case $gl_gcc_version in
+ gcc*' ('*') '?.* | gcc*' ('*') '1[[0-3]].*)
+ # In GCC < 14 the option either does not exist,
+ # or is accepted but always warns.
+ ;;
+ *)
+ AS_VAR_APPEND([$1], [' -Wuseless-cast'])
+ ;;
+ esac
case $gl_gcc_version in
gcc*' ('*') '?.* | gcc*' ('*') '1[[0-4]].*)
# In GCC < 15 the option either does not exist,
--
2.54.0
