sd-bus: add assert to tell the compiler that the error code is positive

I was hoping it would help with the following gcc warning:
[35/657] Compiling C object src/shared/libsystemd-shared-248.a.p/bus-message-util.c.o
../src/shared/bus-message-util.c: In function ‘bus_message_read_dns_servers’:
../src/shared/bus-message-util.c:165:21: warning: ‘family’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  165 |                 r = in_addr_full_new(family, &a, port, 0, server_name, dns + n);
      |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../src/shared/bus-message-util.c:165:21: warning: ‘port’ may be used uninitialized in this function [-Wmaybe-uninitialized]
../src/shared/bus-message-util.c:165:21: warning: ‘server_name’ may be used uninitialized in this function [-Wmaybe-uninitialized]

It actually doesn't, but the compiler has a point here: the code is specified
in sd_bus_error_map[], and it has no way of knowning that we want it to be a
positive value.

I think this should be an assert, because if this assumption fails, a
programming error has occured, something that'd want to catch.

diff --git a/src/libsystemd/sd-bus/bus-error.c b/src/libsystemd/sd-bus/bus-error.c
index 8da2024a5028ffcfa8776cfb5f66799ad545c1fa..163cbb1a71d334714f48b871f6dd07c7a70ee80d 100644 (file)
--- a/src/libsystemd/sd-bus/bus-error.c
+++ b/src/libsystemd/sd-bus/bus-error.c
@@ -86,8 +86,10 @@ static int bus_error_name_to_errno(const char *name) {
                                 if (m->code == BUS_ERROR_MAP_END_MARKER)
                                         break;
 
-                                if (streq(m->name, name))
+                                if (streq(m->name, name)) {
+                                        assert(m->code > 0);
                                         return m->code;
+                                }
                         }
 
         m = ALIGN_TO_PTR(__start_SYSTEMD_BUS_ERROR_MAP, sizeof(void*));
@@ -103,8 +105,10 @@ static int bus_error_name_to_errno(const char *name) {
                         continue;
                 }
 
-                if (streq(m->name, name))
+                if (streq(m->name, name)) {
+                        assert(m->code > 0);
                         return m->code;
+                }
 
                 m++;
         }