test-genzeros: avoid raw write(2)

This test helper feeds 256kB of data at once to a single invocation
of the write(2) system call, which may be too much for some
platforms.

Call our xwrite() wrapper that knows to honor MAX_IO_SIZE limit and
cope with short writes due to EINTR instead, and die a bit more
loudly by calling die_errno() when xwrite() indicates an error.

Reported-by: Randall S. Becker <[email protected]>
Helped-by: Jeff King <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: gitster

t/helper/test-genzeros.c

@@ -17,15 +17,16 @@ int cmd__genzeros(int argc, const char **argv)
 
 	/* Writing out individual NUL bytes is slow... */
 	while (count < 0)
-		if (write(1, zeros, ARRAY_SIZE(zeros)) < 0)
-			return -1;
+		if (xwrite(1, zeros, ARRAY_SIZE(zeros)) < 0)
+			die_errno("write error");
 
 	while (count > 0) {
-		n = write(1, zeros, count < ARRAY_SIZE(zeros) ?
-			  count : ARRAY_SIZE(zeros));
+		n = xwrite(1, zeros,
+			   count < ARRAY_SIZE(zeros)
+			   ? count : ARRAY_SIZE(zeros));
 
 		if (n < 0)
-			return -1;
+			die_errno("write error");
 
 		count -= n;
 	}