oslib-win32: only provide localtime_r/gmtime_r if missing

The oslib-win32 file currently provides a localtime_r and
gmtime_r replacement unconditionally. Some versions of
Mingw-w64 would provide crude macros for localtime_r/gmtime_r
which QEMU takes care to disable. Latest versions of Mingw-w64
now provide actual functions for localtime_r/gmtime_r, but
with a twist that you have to include unistd.h or pthread.h
before including time.h.  By luck some files in QEMU have
such an include order, resulting in compile errors:

  CC    util/osdep.o
In file included from include/qemu-common.h:48:0,
                 from util/osdep.c:48:
include/sysemu/os-win32.h:77:12: error: redundant redeclaration of 'gmtime_r' [-Werror=redundant-decls]
 struct tm *gmtime_r(const time_t *timep, struct tm *result);
            ^
In file included from include/qemu-common.h:35:0,
                 from util/osdep.c:48:
/usr/i686-w64-mingw32/sys-root/mingw/include/time.h:272:107: note: previous definition of 'gmtime_r' was here
In file included from include/qemu-common.h:48:0,
                 from util/osdep.c:48:
include/sysemu/os-win32.h:79:12: error: redundant redeclaration of 'localtime_r' [-Werror=redundant-decls]
 struct tm *localtime_r(const time_t *timep, struct tm *result);
            ^
In file included from include/qemu-common.h:35:0,
                 from util/osdep.c:48:
/usr/i686-w64-mingw32/sys-root/mingw/include/time.h:269:107: note: previous definition of 'localtime_r' was here

This change adds a configure test to see if localtime_r
exits, and only enables the QEMU impl if missing. We also
re-arrange qemu-common.h try attempt to guarantee that all
source files get unistd.h before time.h and thus see the
localtime_r/gmtime_r defs.

[sw: Use "official" spellings for Mingw-w64, MinGW in comments.]
[sw: Terminate sentences with a dot in comments.]

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Reviewed-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: Stefan Weil <sw@weilnetz.de>

1 files changed, 34 insertions, 0 deletions

diff --git a/configure b/configure
index 29009ee6d8..f14454e691 100755
--- a/configure
+++ b/configure
@@ -1737,6 +1737,37 @@ else
 fi
 
 ##########################################
+# MinGW / Mingw-w64 localtime_r/gmtime_r check
+
+if test "$mingw32" = "yes"; then
+    # Some versions of MinGW / Mingw-w64 lack localtime_r
+    # and gmtime_r entirely.
+    #
+    # Some versions of Mingw-w64 define a macro for
+    # localtime_r/gmtime_r.
+    #
+    # Some versions of Mingw-w64 will define functions
+    # for localtime_r/gmtime_r, but only if you have
+    # _POSIX_THREAD_SAFE_FUNCTIONS defined. For fun
+    # though, unistd.h and pthread.h both define
+    # that for you.
+    #
+    # So this #undef localtime_r and #include <unistd.h>
+    # are not in fact redundant.
+cat > $TMPC << EOF
+#include <unistd.h>
+#include <time.h>
+#undef localtime_r
+int main(void) { localtime_r(NULL, NULL); return 0; }
+EOF
+    if compile_prog "" "" ; then
+        localtime_r="yes"
+    else
+        localtime_r="no"
+    fi
+fi
+
+##########################################
 # pkg-config probe
 
 if ! has "$pkg_config_exe"; then
@@ -5034,6 +5065,9 @@ fi
 if test "$zero_malloc" = "yes" ; then
   echo "CONFIG_ZERO_MALLOC=y" >> $config_host_mak
 fi
+if test "$localtime_r" = "yes" ; then
+  echo "CONFIG_LOCALTIME_R=y" >> $config_host_mak
+fi
 if test "$qom_cast_debug" = "yes" ; then
   echo "CONFIG_QOM_CAST_DEBUG=y" >> $config_host_mak
 fi