fix bug in (and test) futimesat

bigbro-linux.c

@@ -369,7 +369,7 @@ static int save_syscall_access(pid_t child, rw_status *h) {
       int retval = wait_for_return_value(child, h);
       debugprintf("%d: %s(%d, '%s') -> %d\n", child, name,
                   dirfd, arg, retval);
-      if (retval >= 0) read_file_at(child, dirfd, arg, h);
+      if (retval >= 0) write_file_at(child, dirfd, arg, h);
       free(arg);
     } else {
       int retval = wait_for_return_value(child, h);

tests/futimesat.c

@@ -0,0 +1,34 @@
+#define _POSIX_C_SOURCE 200809L
+#define _GNU_SOURCE
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/time.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <errno.h>
+
+// NOTE: futimesat is obsolete (in favor of utimesat), but we should
+// still support any programs that might use it.
+
+int main() {
+  int subd = openat(AT_FDCWD, "tmp/subdir1", O_RDONLY | O_DIRECTORY);
+  struct timeval *ts = NULL;
+
+  // the following should all fail, but should also not cause a crash
+  // that would prevent the following utimensat from being traced.
+  futimesat(subd, "foo_symlink_typo", ts);
+  // The following is a way to silence a warning on using a null
+  // pointer here.  We are intentionally giving a bad value to ensure
+  // it doesn't screw up bigbro.
+  char *mynull = ((char *)5) - 5;
+  futimesat(subd, mynull, ts);
+  futimesat(subd, "", ts);
+
+  int retval = futimesat(subd, "foo_symlink", ts);
+  if (retval < 0) {
+    perror("trouble");
+  }
+  printf("retval was %d\n", retval);
+  return 0;
+}

tests/futimesat.py

@@ -0,0 +1,14 @@
+import re
+
+import tests.helper as th
+
+def passes(out, err):
+    return all(
+        [th.reads(err, '/tests/futimesat.test'),
+         th.writes(err, '/tmp/foo'),
+         th.count_writes(err, 1),
+         th.count_readdir(err, 0),
+     ])
+
+needs_symlinks = False
+skip_windows = True