Eli Zaretskii wrote:
> > Do you know how to distinguish the two, just by preprocessor defines,
> > without any autoconf test?
>
> AFAIK, it's tricky, because MinGW64 also defines __MINGW32__, and
> doesn't have any macro specific to it that is defined by the compiler
> itself. In Emacs we use this ugly hack to resolve the problem:
>
> /* MinGW-w64 gcc does not automatically define a macro for
> differentiating it fom MinGW gcc. We need to test the presence of
> __MINGW64_VERSION_MAJOR in _mingw.h: */
> #ifdef __MINGW32__
> # include <_mingw.h>
> # ifdef __MINGW64_VERSION_MAJOR
> # define MINGW_W64
> # endif
> #endif
>
> and then test MINGW_W64 elsewhere.
Thanks for showing this. But this seems to introduce more, not less fragility.
I don't want to revert the #if, i.e. prefer fseeko64 to _fseeki64, because
the idea of mingw is to use the maximum of functions from the CRT DLLs.
So I ended up adding the test for the declaration of _fseeki64:
2018-05-12 Bruno Haible <br...@clisp.org>
fseeko: On mingw, don't use the hidden function _fseeki64.
Reported by Eli Zaretskii <e...@gnu.org>.
* m4/fseeko.m4 (gl_PREREQ_FSEEKO): Test whether _fseeki64 is declared.
* lib/fseeko.c (fseeko): Use _fseeki64 only if it is declared.
diff --git a/m4/fseeko.m4 b/m4/fseeko.m4
index 8967cf1..86c246e 100644
--- a/m4/fseeko.m4
+++ b/m4/fseeko.m4
@@ -1,4 +1,4 @@
-# fseeko.m4 serial 18
+# fseeko.m4 serial 19
dnl Copyright (C) 2007-2018 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
@@ -68,7 +68,10 @@ AC_DEFUN([gl_STDIN_LARGE_OFFSET],
# Prerequisites of lib/fseeko.c.
AC_DEFUN([gl_PREREQ_FSEEKO],
[
- dnl Native Windows has the function _fseeki64. mingw hides it, but mingw64
- dnl makes it usable again.
+ dnl Native Windows has the function _fseeki64. mingw hides it in some
+ dnl circumstances, but mingw64 makes it usable again.
AC_CHECK_FUNCS([_fseeki64])
+ if test $ac_cv_func__fseeki64 = yes; then
+ AC_CHECK_DECLS([_fseeki64])
+ fi
])
diff --git a/lib/fseeko.c b/lib/fseeko.c
index e5c5172..d47481d 100644
--- a/lib/fseeko.c
+++ b/lib/fseeko.c
@@ -33,9 +33,9 @@ fseeko (FILE *fp, off_t offset, int whence)
#endif
#if _GL_WINDOWS_64_BIT_OFF_T
# undef fseeko
-# if HAVE__FSEEKI64 /* msvc, mingw64 */
+# if HAVE__FSEEKI64 && HAVE_DECL__FSEEKI64 /* msvc, mingw since msvcrt8.0,
mingw64 */
# define fseeko _fseeki64
-# else /* mingw */
+# else /* mingw before msvcrt8.0 */
# define fseeko fseeko64
# endif
#endif
