On mingw-w64 with UCRT option, I see this compilation error:
gcc -std=gnu23 -DHAVE_CONFIG_H -DEXEEXT=\".exe\" -DEXEEXT=\".exe\" -I.
-I../../gltests -I.. -DGNULIB_STRICT_CHECKING=1 -DIN_GNULIB_TESTS=1 -I.
-I../../gltests -I.. -I../../gltests/.. -I../gllib -I../../gltests/../gllib
-I/usr/local/ucrt64/include -Wall -Wno-error -g -O2 -c -o test-btowc.o
../../gltests/test-btowc.c
In file included from ../../gltests/test-btowc.c:23:
../../gltests/test-btowc.c:24:18: error: initialization of 'rpl_wint_t
(*)(int)' {aka 'unsigned int (*)(int)'} from incompatible pointer type 'wint_t
(*)(int)' {aka 'short unsigned int (*)(int)'} [-Wincompatible-pointer-types]
24 | SIGNATURE_CHECK (btowc, wint_t, (int));
| ^~~~~
../../gltests/signature.h:46:57: note: in definition of macro 'SIGNATURE_CHECK2'
46 | _GL_UNUSED static ret (*signature_check ## id) args = fn
| ^~
../../gltests/signature.h:39:3: note: in expansion of macro 'SIGNATURE_CHECK1'
39 | SIGNATURE_CHECK1 (fn, ret, args, __LINE__)
| ^~~~~~~~~~~~~~~~
../../gltests/test-btowc.c:24:1: note: in expansion of macro 'SIGNATURE_CHECK'
24 | SIGNATURE_CHECK (btowc, wint_t, (int));
| ^~~~~~~~~~~~~~~
make[4]: *** [Makefile:27542: test-btowc.o] Error 1
I recall having seen this as a warning (with older mingw or with MSVC).
But gcc 14, which is in use here, is stricter and does not allow an implicit
conversion from
unsigned short (*)(int)
to
unsigned int (*)(int)
(because in ISO C, argument promotion happens for the parameters, but not for
the result type).
This patch fixes it.
2024-12-22 Bruno Haible <br...@clisp.org>
btowc: Fix declaration on mingw/ucrt.
* m4/btowc.m4 (gl_FUNC_BTOWC): Require gt_TYPE_WINT_T. If gnulib
overrides wint_t, set REPLACE_BTOWC to 1.
diff --git a/m4/btowc.m4 b/m4/btowc.m4
index e5cab9662c..1aa12130e0 100644
--- a/m4/btowc.m4
+++ b/m4/btowc.m4
@@ -1,5 +1,5 @@
# btowc.m4
-# serial 14
+# serial 15
dnl Copyright (C) 2008-2024 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
@@ -9,6 +9,7 @@
AC_DEFUN([gl_FUNC_BTOWC],
[
AC_REQUIRE([gl_WCHAR_H_DEFAULTS])
+ AC_REQUIRE([gt_TYPE_WINT_T])
dnl Check whether <wchar.h> is usable at all, first. Otherwise the test
dnl program below may lead to an endless loop. See
@@ -134,6 +135,13 @@ AC_DEFUN([gl_FUNC_BTOWC]
])
])
+ if test $GNULIBHEADERS_OVERRIDE_WINT_T = 1; then
+ dnl On mingw/ucrt, we override the return type of btowc().
+ dnl While the original wint_t (= unsigned short) and the overridden
wint_t
+ dnl (= unsigned int) are equivalent in function parameters, this is not
+ dnl the case for function return types.
+ REPLACE_BTOWC=1
+ fi
case "$gl_cv_func_btowc_nul" in
*yes) ;;
*) REPLACE_BTOWC=1 ;;
