[PATCH v6 4/4] win32: Simplify gmtime_r detection not depends on if _POSIX_C_SOURCE are defined on msys2/mingw

[Yonggang Luo <luoyonggang@gmail.com>]

We remove the CONFIG_LOCALTIME_R detection option in configure, and move the check
existence of gmtime_r from configure into C header and source directly by using macro
`_POSIX_THREAD_SAFE_FUNCTIONS`.
Before this patch, the configure script are always assume the compiler doesn't define
_POSIX_C_SOURCE macro at all, but that's not true, because thirdparty library such
as ncursesw may define -D_POSIX_C_SOURCE in it's pkg-config file. And that C Flags will
added -D_POSIX_C_SOURCE into each QEMU_CFLAGS. And that's causing the following compiling error:
n file included from C:/work/xemu/qemu/include/qemu/osdep.h:119,
                 from ../softmmu/main.c:25:
C:/work/xemu/qemu/include/sysemu/os-win32.h:53:12: error: redundant redeclaration of 'gmtime_r' [-Werror=redundant-decls]
   53 | struct tm *gmtime_r(const time_t *timep, struct tm *result);
      |            ^~~~~~~~
In file included from C:/work/xemu/qemu/include/qemu/osdep.h:94,
                 from ../softmmu/main.c:25:
C:/CI-Tools/msys64/mingw64/x86_64-w64-mingw32/include/time.h:284:36: note: previous definition of 'gmtime_r' was here
  284 | __forceinline struct tm *__CRTDECL gmtime_r(const time_t *_Time, struct tm *_Tm) {
      |                                    ^~~~~~~~
In file included from C:/work/xemu/qemu/include/qemu/osdep.h:119,
                 from ../softmmu/main.c:25:
C:/work/xemu/qemu/include/sysemu/os-win32.h:55:12: error: redundant redeclaration of 'localtime_r' [-Werror=redundant-decls]
   55 | struct tm *localtime_r(const time_t *timep, struct tm *result);
      |            ^~~~~~~~~~~
In file included from C:/work/xemu/qemu/include/qemu/osdep.h:94,
                 from ../softmmu/main.c:25:
C:/CI-Tools/msys64/mingw64/x86_64-w64-mingw32/include/time.h:281:36: note: previous definition of 'localtime_r' was here
  281 | __forceinline struct tm *__CRTDECL localtime_r(const time_t *_Time, struct tm *_Tm) {
      |                                    ^~~~~~~~~~~
Compiling C object libcommon.fa.p/hw_gpio_zaurus.c.obj
In file included from C:/work/xemu/qemu/include/qemu/osdep.h:119,
                 from ../hw/i2c/smbus_slave.c:16:
C:/work/xemu/qemu/include/sysemu/os-win32.h:53:12: error: redundant redeclaration of 'gmtime_r' [-Werror=redundant-decls]
   53 | struct tm *gmtime_r(const time_t *timep, struct tm *result);
      |            ^~~~~~~~
In file included from C:/work/xemu/qemu/include/qemu/osdep.h:94,
                 from ../hw/i2c/smbus_slave.c:16:
C:/CI-Tools/msys64/mingw64/x86_64-w64-mingw32/include/time.h:284:36: note: previous definition of 'gmtime_r' was here
  284 | __forceinline struct tm *__CRTDECL gmtime_r(const time_t *_Time, struct tm *_Tm) {
      |                                    ^~~~~~~~
In file included from C:/work/xemu/qemu/include/qemu/osdep.h:119,
                 from ../hw/i2c/smbus_slave.c:16:
C:/work/xemu/qemu/include/sysemu/os-win32.h:55:12: error: redundant redeclaration of 'localtime_r' [-Werror=redundant-decls]
   55 | struct tm *localtime_r(const time_t *timep, struct tm *result);
      |            ^~~~~~~~~~~
In file included from C:/work/xemu/qemu/include/qemu/osdep.h:94,
                 from ../hw/i2c/smbus_slave.c:16:
C:/CI-Tools/msys64/mingw64/x86_64-w64-mingw32/include/time.h:281:36: note: previous definition of 'localtime_r' was here
  281 | __forceinline struct tm *__CRTDECL localtime_r(const time_t *_Time, struct tm *_Tm) {
      |                                    ^~~~~~~~~~~
Compiling C object libcommon.fa.p/hw_dma_xilinx_axidma.c.obj

After this patch, whenever ncursesw or other thirdparty libraries tried to define or not
define  _POSIX_C_SOURCE, the source will building properly. Because now, we don't make any
assumption if _POSIX_C_SOURCE are defined. We solely relied on if the macro `_POSIX_THREAD_SAFE_FUNCTIONS`
are defined in msys2/mingw header.

The _POSIX_THREAD_SAFE_FUNCTIONS are defined in mingw header like this:

```
#if defined(_POSIX_C_SOURCE) && !defined(_POSIX_THREAD_SAFE_FUNCTIONS)
#define _POSIX_THREAD_SAFE_FUNCTIONS 200112L
#endif

#ifdef _POSIX_THREAD_SAFE_FUNCTIONS
__forceinline struct tm *__CRTDECL localtime_r(const time_t *_Time, struct tm *_Tm) {
  return localtime_s(_Tm, _Time) ? NULL : _Tm;
}
__forceinline struct tm *__CRTDECL gmtime_r(const time_t *_Time, struct tm *_Tm) {
  return gmtime_s(_Tm, _Time) ? NULL : _Tm;
}
__forceinline char *__CRTDECL ctime_r(const time_t *_Time, char *_Str) {
  return ctime_s(_Str, 0x7fffffff, _Time) ? NULL : _Str;
}
__forceinline char *__CRTDECL asctime_r(const struct tm *_Tm, char * _Str) {
  return asctime_s(_Str, 0x7fffffff, _Tm) ? NULL : _Str;
}
#endif
```

Signed-off-by: Yonggang Luo <luoyonggang@gmail.com>
---
 configure                 | 34 ----------------------------------
 include/sysemu/os-win32.h |  4 ++--
 util/oslib-win32.c        |  4 ++--
 3 files changed, 4 insertions(+), 38 deletions(-)

diff --git a/configure b/configure
index 8f7bdbfdd3..d6dd147235 100755
--- a/configure
+++ b/configure
@@ -2500,37 +2500,6 @@ if test "$vhost_net" = ""; then
   test "$vhost_kernel" = "yes" && vhost_net=yes
 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
 
@@ -6937,9 +6906,6 @@ if [ "$bsd" = "yes" ] ; then
   echo "CONFIG_BSD=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
diff --git a/include/sysemu/os-win32.h b/include/sysemu/os-win32.h
index d8978e28c0..5346d51e89 100644
--- a/include/sysemu/os-win32.h
+++ b/include/sysemu/os-win32.h
@@ -48,12 +48,12 @@
 #define siglongjmp(env, val) longjmp(env, val)
 
 /* Missing POSIX functions. Don't use MinGW-w64 macros. */
-#ifndef CONFIG_LOCALTIME_R
+#ifndef _POSIX_THREAD_SAFE_FUNCTIONS
 #undef gmtime_r
 struct tm *gmtime_r(const time_t *timep, struct tm *result);
 #undef localtime_r
 struct tm *localtime_r(const time_t *timep, struct tm *result);
-#endif /* CONFIG_LOCALTIME_R */
+#endif /* _POSIX_THREAD_SAFE_FUNCTIONS */
 
 static inline void os_setup_signal_handling(void) {}
 static inline void os_daemonize(void) {}
diff --git a/util/oslib-win32.c b/util/oslib-win32.c
index 051afb217b..e99debfb8d 100644
--- a/util/oslib-win32.c
+++ b/util/oslib-win32.c
@@ -106,7 +106,7 @@ void qemu_anon_ram_free(void *ptr, size_t size)
     }
 }
 
-#ifndef CONFIG_LOCALTIME_R
+#ifndef _POSIX_THREAD_SAFE_FUNCTIONS
 /* FIXME: add proper locking */
 struct tm *gmtime_r(const time_t *timep, struct tm *result)
 {
@@ -130,7 +130,7 @@ struct tm *localtime_r(const time_t *timep, struct tm *result)
     }
     return p;
 }
-#endif /* CONFIG_LOCALTIME_R */
+#endif /* _POSIX_THREAD_SAFE_FUNCTIONS */
 
 static int socket_error(void)
 {
-- 
2.28.0.windows.1