tests: don't mix FILE* and UNIX FD I/O on same stream

There is currently a hang in test27 that exhibits itself on FreeBSD 11.4
only. The behaviour is that virCommandProcessIO gets POLLIN on the
FD for stdout, but read() blocks. Meanwhile commandtest also blocks
in write for stderr because the pipe buffers are full.

This fix in commandhelper likely does not really address the root cause
just hides it due to the buffering done by FILE *. Mixing UNIX FD I/O
and FILE * I/O is bad practice regardless.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

diff --git a/tests/commandhelper.c b/tests/commandhelper.c
index 05f577730f636472085baf4bd071cc45af70f674..7c260c4e135a349a52aa96d96bda863db77872d5 100644 (file)
--- a/tests/commandhelper.c
+++ b/tests/commandhelper.c
@@ -221,9 +221,9 @@ int main(int argc, char **argv) {
     }
 
     for (i = 0; i < numpollfds; i++) {
-        if (write(STDOUT_FILENO, buffers[i], buflen[i]) != buflen[i])
+        if (fwrite(buffers[i], 1, buflen[i], stdout) != buflen[i])
             goto cleanup;
-        if (write(STDERR_FILENO, buffers[i], buflen[i]) != buflen[i])
+        if (fwrite(buffers[i], 1, buflen[i], stderr) != buflen[i])
             goto cleanup;
     }