Avoid passing NULL to printf's %s if argc == 0

This is undefined behaviour even if most libcs handle it gracefully.

3 files changed, 4 insertions, 3 deletions

diff --git a/compare/compare.c b/compare/compare.c
index ee1966b..3cb3cff 100644
--- a/compare/compare.c
+++ b/compare/compare.c
@@ -570,7 +570,7 @@ fail:
     free(pos);
     const char *fmt =
         "Usage: %s ([-i] <input-dir>)+ [-o <output-dir>] [-s <scale:1-8>] [-p <pass-level:0-3>]\n";
-    printf(fmt, argv[0]);
+    printf(fmt, argv[0] ? argv[0] : "compare");
     return NULL;
 }
 
diff --git a/profile/profile.c b/profile/profile.c
index 3740a6c..28b818d 100644
--- a/profile/profile.c
+++ b/profile/profile.c
@@ -68,7 +68,8 @@ int main(int argc, char *argv[])
     const int frame_h = 720;
 
     if (argc < 5) {
-        printf("usage: %s <subtitle file> <start time> <fps> <end time>\n", argv[0]);
+        printf("usage: %s <subtitle file> <start time> <fps> <end time>\n",
+               argv[0] ? argv[0] : "profile");
         exit(1);
     }
     char *subfile = argv[1];
diff --git a/test/test.c b/test/test.c
index f1de28f..b9754c9 100644
--- a/test/test.c
+++ b/test/test.c
@@ -199,7 +199,7 @@ int main(int argc, char *argv[])
     if (argc != 4 && argc != 6) {
         printf("usage: %s <image file> <subtitle file> <time> "
                "[<storage width> <storage height>]\n",
-                argv[0]);
+                argv[0] ? argv[0] : "test");
         exit(1);
     }
     char *imgfile = argv[1];