failtest: report errors in children directly to original stderr.

[ccan] / ccan / failtest / failtest.c

diff --git a/ccan/failtest/failtest.c b/ccan/failtest/failtest.c
index f59ed03acf4abc70f48c8779fabf6684ab724444..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;
 
@@ -95,6 +96,24 @@ static struct failtest_call *add_history_(enum failtest_call_type type,
 #define set_cleanup(call, clean, type)                 \
        (call)->cleanup = (void *)((void)sizeof(clean((type *)NULL),1), (clean))
 
+
+/* Dup the fd to a high value (out of the way I hope!), and close the old fd. */
+static int move_fd_to_high(int fd)
+{
+       int i;
+
+       for (i = FD_SETSIZE - 1; i >= 0; i--) {
+               if (fcntl(i, F_GETFL) == -1 && errno == EBADF) {
+                       if (dup2(fd, i) == -1)
+                               err(1, "Failed to dup fd %i to %i", fd, i);
+                       close(fd);
+                       return i;
+               }
+       }
+       /* Nothing?  Really?  Er... ok? */
+       return fd;
+}
+
 static bool read_write_info(int fd)
 {
        struct write_call *w;
@@ -132,6 +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)
@@ -493,7 +543,7 @@ static bool should_fail(struct failtest_call *call)
                dup2(output[1], STDERR_FILENO);
                if (output[1] != STDOUT_FILENO && output[1] != STDERR_FILENO)
                        close(output[1]);
-               control_fd = control[1];
+               control_fd = move_fd_to_high(control[1]);
                /* Valgrind spots the leak if we don't free these. */
                free_files(files);
                return true;
@@ -1067,12 +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 = dup(STDERR_FILENO);
+                       tracefd = warnfd;
                        failtest_timeout_ms = -1;
                } else if (!strncmp(argv[i], "--debugpath=",
                                    strlen("--debugpath="))) {