Main: Add a result code sanitizer

Improves the exit status code.

diff --git a/src/main.c b/src/main.c
index 89cda3113c96d5d4c5d17b86b3403b057ce1d49f..790f2a37f606f4cebf547cb1bc3ca4d1c13bdc7c 100644 (file)
--- a/src/main.c
+++ b/src/main.c
@@ -29,6 +29,39 @@ run_rtr_server(void)
        return error;
 }
 
+/**
+ * Shells don't like it when we return values other than 0-255.
+ * In fact, bash also has its own meanings for 126-255.
+ * (See man 1 bash > EXIT STATUS)
+ *
+ * This function shifts @error to our exclusive range.
+ */
+static int
+convert_to_result(int error)
+{
+       if (error == 0)
+               return 0; /* Happy path */
+
+       /* -INT_MIN overflows, So handle weird case. */
+       if (error == INT_MIN)
+               return 125;
+
+       /* Force range 0-127 */
+       if (error < 0)
+               error = -error;
+       error &= 0x7F;
+
+       switch (error) {
+       case 126:
+               return 122;
+       case 127:
+               return 123;
+       case 0:
+               return 124; /* was divisible by 128; force error. */
+       }
+       return error;
+}
+
 int
 main(int argc, char **argv)
 {
@@ -115,5 +148,5 @@ revert_config:
 revert_log:
        log_teardown();
 just_quit:
-       return abs(error);
+       return convert_to_result(error);
 }