failtest: report errors in children directly to original stderr.

This is useful for debugging failtest itself, as well as for things
like tracing.

diff --git a/ccan/failtest/failtest.c b/ccan/failtest/failtest.c
index 2ff265f1508b3f7e194e0a1fe4048136b3c06bbe..0d52a7969b783ddb7bafd60b53d8f72d5cbdf92d 100644 (file)
--- a/ccan/failtest/failtest.c
+++ b/ccan/failtest/failtest.c
@@ -24,6 +24,7 @@
 enum failtest_result (*failtest_hook)(struct tlist_calls *);
 
 static int tracefd = -1;
+static int warnfd;
 
 unsigned int failtest_timeout_ms = 20000;
 
@@ -150,6 +151,37 @@ static char *failpath_string(void)
        return ret;
 }
 
+static void warn_via_fd(int e, const char *fmt, va_list ap)
+{
+       char *p = failpath_string();
+
+       vdprintf(warnfd, fmt, ap);
+       if (e != -1)
+               dprintf(warnfd, ": %s", strerror(e));
+       dprintf(warnfd, " [%s]\n", p);
+       free(p);
+}
+
+static void fwarn(const char *fmt, ...)
+{
+       va_list ap;
+       int e = errno;
+
+       va_start(ap, fmt);
+       warn_via_fd(e, fmt, ap);
+       va_end(ap);
+}
+
+
+static void fwarnx(const char *fmt, ...)
+{
+       va_list ap;
+
+       va_start(ap, fmt);
+       warn_via_fd(-1, fmt, ap);
+       va_end(ap);
+}
+
 static void tell_parent(enum info_type type)
 {
        if (control_fd != -1)
@@ -1085,12 +1117,13 @@ void failtest_init(int argc, char *argv[])
        unsigned int i;
 
        orig_pid = getpid();
-               
+
+       warnfd = move_fd_to_high(dup(STDERR_FILENO));
        for (i = 1; i < argc; i++) {
                if (!strncmp(argv[i], "--failpath=", strlen("--failpath="))) {
                        failpath = argv[i] + strlen("--failpath=");
                } else if (strcmp(argv[i], "--tracepath") == 0) {
-                       tracefd = move_fd_to_high(STDERR_FILENO);
+                       tracefd = warnfd;
                        failtest_timeout_ms = -1;
                } else if (!strncmp(argv[i], "--debugpath=",
                                    strlen("--debugpath="))) {