compat/mingw: support MSys2-based MinGW build

The excellent MSys2 project brings a substantially updated MinGW
environment including newer GCC versions and new headers. To support
compiling Git, let's special-case the new MinGW (tell-tale: the
_MINGW64_VERSION_MAJOR constant is defined).

Note: this commit only addresses compile failures, not compile warnings
(that task is left for a future patch).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

compat/mingw.h

@@ -1,14 +1,26 @@
+#ifdef __MINGW64_VERSION_MAJOR
+#include <stdint.h>
+#include <wchar.h>
+typedef _sigset_t sigset_t;
+#endif
 #include <winsock2.h>
 #include <ws2tcpip.h>
 
+/* MinGW-w64 reports to have flockfile, but it does not actually have it. */
+#ifdef __MINGW64_VERSION_MAJOR
+#undef _POSIX_THREAD_SAFE_FUNCTIONS
+#endif
+
 /*
  * things that are not available in header files
  */
 
-typedef int pid_t;
 typedef int uid_t;
 typedef int socklen_t;
+#ifndef __MINGW64_VERSION_MAJOR
+typedef int pid_t;
 #define hstrerror strerror
+#endif
 
 #define S_IFLNK    0120000 /* Symbolic link */
 #define S_ISLNK(x) (((x) & S_IFMT) == S_IFLNK)
@@ -100,8 +112,10 @@ static inline int symlink(const char *oldpath, const char *newpath)
 { errno = ENOSYS; return -1; }
 static inline int fchmod(int fildes, mode_t mode)
 { errno = ENOSYS; return -1; }
+#ifndef __MINGW64_VERSION_MAJOR
 static inline pid_t fork(void)
 { errno = ENOSYS; return -1; }
+#endif
 static inline unsigned int alarm(unsigned int seconds)
 { return 0; }
 static inline int fsync(int fd)
@@ -176,8 +190,10 @@ int pipe(int filedes[2]);
 unsigned int sleep (unsigned int seconds);
 int mkstemp(char *template);
 int gettimeofday(struct timeval *tv, void *tz);
+#ifndef __MINGW64_VERSION_MAJOR
 struct tm *gmtime_r(const time_t *timep, struct tm *result);
 struct tm *localtime_r(const time_t *timep, struct tm *result);
+#endif
 int getpagesize(void);	/* defined in MinGW's libgcc.a */
 struct passwd *getpwuid(uid_t uid);
 int setitimer(int type, struct itimerval *in, struct itimerval *out);
@@ -301,8 +317,10 @@ static inline int getrlimit(int resource, struct rlimit *rlp)
 /*
  * Use mingw specific stat()/lstat()/fstat() implementations on Windows.
  */
+#ifndef __MINGW64_VERSION_MAJOR
 #define off_t off64_t
 #define lseek _lseeki64
+#endif
 
 /* use struct stat with 64 bit st_size */
 #ifdef stat
@@ -375,8 +393,12 @@ static inline char *mingw_find_last_dir_sep(const char *path)
 int mingw_offset_1st_component(const char *path);
 #define offset_1st_component mingw_offset_1st_component
 #define PATH_SEP ';'
+#ifndef __MINGW64_VERSION_MAJOR
 #define PRIuMAX "I64u"
 #define PRId64 "I64d"
+#else
+#include <inttypes.h>
+#endif
 
 void mingw_open_html(const char *path);
 #define open_html mingw_open_html