strerror_r breakage on mingw

[Bruno Haible]

When I create a testdir
  $ ./gnulib-tool --create-testdir --dir=../testdir-utime --single-configure 
fdutimensat futimens utimensat utimens
and compile it on mingw, I get this warning and compilation error:


i686-w64-mingw32-gcc -DHAVE_CONFIG_H -I. -I../../gllib -I..  
-DGNULIB_STRICT_CHECKING=1 -I/usr/local/mingw32/include -Wall  -g -O2 -MT 
error.o -MD -MP -MF .deps/error.Tpo -c -o error.o ../../gllib/error.c
../../gllib/error.c: In function ‘print_errno_message’:
../../gllib/error.c:121:24: warning: implicit declaration of function 
‘strerror_r’ [-Wimplicit-function-declaration]
 #  define __strerror_r strerror_r
                        ^
../../gllib/error.c:180:7: note: in expansion of macro ‘__strerror_r’
   if (__strerror_r (errnum, errbuf, sizeof errbuf) == 0)
       ^

i686-w64-mingw32-gcc  -g -O2  -L/usr/local/mingw32/lib -o test-fdutimensat.exe 
test-fdutimensat.o libtests.a ../gllib/libgnu.a libtests.a   -lws2_32  
libtests.a(strerror_r.o): In function `strerror_r':
/home/bruno/testdir-utime/build-mingw32/gltests/../../gltests/strerror_r.c:164: 
undefined reference to `strerror_override'
collect2: error: ld returned 1 exit status
make[4]: *** [Makefile:2302: test-fdutimensat.exe] Error 1


The problem is that HAVE_STRERROR_R is now defined to 1 in config.h:

/* Define to 1, since you should have the function strerror_r. */
#define HAVE_STRERROR_R 1

but strerror_r is not defined in gllib, only in gltests.


The underlying problem is that m4/argp.m4 and m4/error.m4 invoke
AC_FUNC_STRERROR_R. The modules 'argp' and 'error' depend on 'strerror'
but actually, in a multithreaded environment, require 'strerror_r'.
Therefore the code currently tries a "use module strerror_r optionally"
strategy, which is not supported by gnulib-tool's dependency system.
There is now a doc section that describes how this can be done correctly.
The previous way is incorrect. I'm reverting the patches from
2016-10-16 [1], 2016-11-04 [2], 2016-11-14 [3], and implementing a correct fix
of the second problem from [1] instead:

   When the strerror_r-posix module is in place, the results of
   AC_FUNC_STRERROR_R have to be ignored, because they don't reflect the
   situation after
     #define strerror_r rpl_strerror_r

[1] https://lists.gnu.org/archive/html/bug-gnulib/2016-10/msg00069.html
[2] https://lists.gnu.org/archive/html/bug-gnulib/2016-11/msg00043.html
[3] https://lists.gnu.org/archive/html/bug-gnulib/2016-11/msg00054.html


2017-04-23  Bruno Haible  <address@hidden>

        Fix conflict between strerror_r-posix module and AC_FUNC_STRERROR_R.
        * modules/strerror_r-posix (configure.ac): Invoke gl_MODULE_INDICATOR.
        * lib/error.c: Test GNULIB_STRERROR_R_POSIX before testing
        HAVE_DECL_STRERROR_R, HAVE_STRERROR_R, or STRERROR_R_CHAR_P.
        * lib/argp-help.c (__argp_failure): Likewise.

diff --git a/lib/argp-help.c b/lib/argp-help.c
index 5567eee..ae639bd 100644
--- a/lib/argp-help.c
+++ b/lib/argp-help.c
@@ -1873,8 +1873,8 @@ __argp_failure (const struct argp_state *state, int 
status, int errnum,
               char const *s = NULL;
               putc_unlocked (':', stream);
               putc_unlocked (' ', stream);
-# if HAVE_DECL_STRERROR_R
-#  if STRERROR_R_CHAR_P
+# if GNULIB_STRERROR_R_POSIX || HAVE_DECL_STRERROR_R
+#  if GNULIB_STRERROR_R_POSIX || STRERROR_R_CHAR_P
               s = __strerror_r (errnum, buf, sizeof buf);
 #  else
               if (__strerror_r (errnum, buf, sizeof buf) == 0)
diff --git a/lib/error.c b/lib/error.c
index 0ed7c86..feda720 100644
--- a/lib/error.c
+++ b/lib/error.c
@@ -104,7 +104,7 @@ extern void __error_at_line (int status, int errnum, const 
char *file_name,
 /* The gnulib override of fcntl is not needed in this file.  */
 # undef fcntl
 
-# if !HAVE_DECL_STRERROR_R
+# if !(GNULIB_STRERROR_R_POSIX || HAVE_DECL_STRERROR_R)
 #  ifndef HAVE_DECL_STRERROR_R
 "this configure-time declaration test was not run"
 #  endif
@@ -117,9 +117,9 @@ int strerror_r (int errnum, char *buf, size_t buflen);
 
 #define program_name getprogname ()
 
-# if HAVE_STRERROR_R || defined strerror_r
+# if GNULIB_STRERROR_R_POSIX || HAVE_STRERROR_R || defined strerror_r
 #  define __strerror_r strerror_r
-# endif /* HAVE_STRERROR_R || defined strerror_r */
+# endif /* GNULIB_STRERROR_R_POSIX || HAVE_STRERROR_R || defined strerror_r */
 #endif  /* not _LIBC */
 
 #if !_LIBC
@@ -172,9 +172,9 @@ print_errno_message (int errnum)
 {
   char const *s;
 
-#if defined HAVE_STRERROR_R || _LIBC
+#if _LIBC || GNULIB_STRERROR_R_POSIX || defined HAVE_STRERROR_R
   char errbuf[1024];
-# if _LIBC || STRERROR_R_CHAR_P
+# if _LIBC || GNULIB_STRERROR_R_POSIX || STRERROR_R_CHAR_P
   s = __strerror_r (errnum, errbuf, sizeof errbuf);
 # else
   if (__strerror_r (errnum, errbuf, sizeof errbuf) == 0)
diff --git a/modules/strerror_r-posix b/modules/strerror_r-posix
index e15cf96..f91bc0e 100644
--- a/modules/strerror_r-posix
+++ b/modules/strerror_r-posix
@@ -19,6 +19,8 @@ if test $HAVE_DECL_STRERROR_R = 0 || test $REPLACE_STRERROR_R 
= 1; then
   gl_PREREQ_STRERROR_R
 fi
 gl_STRING_MODULE_INDICATOR([strerror_r])
+dnl For the modules argp, error.
+gl_MODULE_INDICATOR([strerror_r-posix])
 
 Makefile.am: