mingw: emulate write(2) that fails with a SIGPIPE

On Windows, when writing to a pipe fails, errno is always
EINVAL. However, Git expects it to be SIGPIPE.

While write() can set EINVAL on Windows e.g. when the buffer pointer is
NULL, this is not the case for Git's source code, therefore we *know*
that an EINVAL on a pipe is actually an EPIPE.

See https://msdn.microsoft.com/en-us/library/1570wh78.aspx for more
details.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

compat/mingw.h

@@ -225,6 +225,24 @@ FILE *mingw_freopen (const char *filename, const char *otype, FILE *stream);
 int mingw_fflush(FILE *stream);
 #define fflush mingw_fflush
 
+static inline ssize_t mingw_write(int fd, const void *buf, size_t len)
+{
+	ssize_t result = write(fd, buf, len);
+
+	if (result < 0 && errno == EINVAL) {
+		/* check if fd is a pipe */
+		HANDLE h = (HANDLE) _get_osfhandle(fd);
+		if (GetFileType(h) == FILE_TYPE_PIPE)
+			errno = EPIPE;
+		else
+			errno = EINVAL;
+	}
+
+	return result;
+}
+
+#define write mingw_write
+
 int mingw_access(const char *filename, int mode);
 #undef access
 #define access mingw_access