failtest: use high-numbers file descriptors to stay out of the way.

[ccan] / ccan / failtest / failtest.c

diff --git a/ccan/failtest/failtest.c b/ccan/failtest/failtest.c
index f59ed03acf4abc70f48c8779fabf6684ab724444..2ff265f1508b3f7e194e0a1fe4048136b3c06bbe 100644 (file)
--- a/ccan/failtest/failtest.c
+++ b/ccan/failtest/failtest.c
@@ -95,6 +95,24 @@ 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;
@@ -493,7 +511,7 @@ 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;
@@ -1072,7 +1090,7 @@ void failtest_init(int argc, char *argv[])
                if (!strncmp(argv[i], "--failpath=", strlen("--failpath="))) {
                        failpath = argv[i] + strlen("--failpath=");
                } else if (strcmp(argv[i], "--tracepath") == 0) {
-                       tracefd = dup(STDERR_FILENO);
+                       tracefd = move_fd_to_high(STDERR_FILENO);
                        failtest_timeout_ms = -1;
                } else if (!strncmp(argv[i], "--debugpath=",
                                    strlen("--debugpath="))) {