[PATCH] mingw: emulate write(2) that fails with a EPIPE

From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Dec 16, 2015, 12:14 UTC
Message-ID: <01da36219c18373f8507e19035e141d7e56b2d18.1450267413.git.johannes.schindelin@gmx.de>

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

According to the documentation, there are two cases in which write() triggers EINVAL: the buffer is NULL, or the length is odd but the mode is 16-bit Unicode (the broken pipe is not mentioned as possible cause). Git never sets the file mode to anything but binary, therefore we know that errno should actually be EPIPE if it is EINVAL and the buffer is not NULL.

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

This works around t5571.11 failing with v2.6.4 on Windows.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 compat/mingw.h | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/compat/mingw.h b/compat/mingw.h
index 738865c..2aca347 100644
--- a/compat/mingw.h
+++ b/compat/mingw.h
@@ -210,6 +210,24 @@ 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 && buf) {
+		/* 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

-- 
2.6.3.windows.1.300.g1c25e49