[Freeciv-Dev] Assertion failure during savegame load when FREECIV_PATH is set but empty (PR#1341)

[Steven Taschuk <staschuk@xxxxxxxxxxxxxxx>]

= = SYMPTOM = =

When the environment variable FREECIV_PATH is set to an empty string,
and one tries to start the server with a saved game, an assertion fails.

    $ export FREECIV_PATH=
    $ civserver -f civgame-3000.sav
    This is the server for Freeciv version 1.12.0
    You can learn a lot about Freeciv at http://www.freeciv.org/
    2: Loading saved game: civgame-3000.sav
    2: Loading rulesets
    civserver: shared.c:311: skip_leading_spaces: Assertion `s!=((void *)0)' 
failed.
    Aborted

= = DISEASE = =

The problem arises in common/shared.c:602-612.  (Line numbers refer to
the 1.12.0 release.)

    char *path = getenv("FREECIV_PATH");   /* path is "" */
    if (!path) {
      path = DEFAULT_DATA_PATH;
    }
    path = mystrdup(path);

    tok = strtok(path, PATH_SEPARATOR);    /* so strtok returns NULL here */
    do {
      int i;

      tok = skip_leading_spaces(tok);      /* tripping the assertion here */

(Digression:  Being a conscientious bug reporter, I checked these
lines in the current CVS, and found this:
    path = getenv("FREECIV_PATH");
    if (!path) {
      path = DEFAULT_DATA_PATH;
    }
    assert(path != NULL);
This assertion seems a bit strange, since it can only fail if the
compile-time constant DEFAULT_DATA_PATH is NULL.  But why not check
this at compile time?)

= = SUGGESTED CURE = =

Obviously having FREECIV_PATH set but empty is a misconfiguration;
nevertheless there is a bug here, to wit, the server's graceless
reaction to the situation.  I suggest the following patch.

--- common/shared.c.distribution        Sat Mar 23 11:12:02 2002
+++ common/shared.c     Sat Mar 23 12:38:22 2002
@@ -602,6 +602,10 @@
     char *path = getenv("FREECIV_PATH");
     if (!path) {
       path = DEFAULT_DATA_PATH;
+    } else if (*path == '\0') {
+      freelog( LOG_ERROR, _("FREECIV_PATH is set but empty; "
+                            "using default path instead.") );
+      path = DEFAULT_DATA_PATH;
     }
     path = mystrdup(path);     /* something we can strtok */

This code notices the misconfiguration and adapts in a sensible way,
producing an informative error message in the log.