support: Preserve errno in write_message, TEST_VERIFY and other checks

These facilities could clobber errno, which makes it difficult to write
certain checks because a specific order has to be used.

1 files changed, 3 insertions, 0 deletions

diff --git a/support/write_message.c b/support/write_message.c
index 9d0f267a2f..a3e2f90535 100644
--- a/support/write_message.c
+++ b/support/write_message.c
@@ -18,12 +18,15 @@
 
 #include <support/support.h>
 
+#include <errno.h>
 #include <string.h>
 #include <unistd.h>
 
 void
 write_message (const char *message)
 {
+  int saved_errno = errno;
   ssize_t unused __attribute__ ((unused));
   unused = write (STDOUT_FILENO, message, strlen (message));
+  errno = saved_errno;
 }