Re: [AD] Mac OS X: file_exists bus error

["Peter Hull" <peterhull90@xxxxxxxxxx>]

I think this is not Mac specific.
file_exists uses al_findfirst, and al_findfirst takes a shortcut if
there are no wildcards in the path specified (src/unix/ufile.c:336) In
this case, the 'dir' member of the find info is unused. (If there are
wildcards, it holds the opendir structure)
The problem is that al_findclose calls closedir regardless.
Patch attached.

Pete


On 5/31/06, Jay Bernardo <allegrolist@xxxxxxxxxx> wrote:
> In the latest revision of the 4.2 branch of Allegro code (5817 at time of
> writing) there is a problem with the file_exists function. Apparently, if
> the specific file you're looking for does not exist, nothing bad happens (it
> operates as intended). However, if it does exist, we get a bus error. I'm
> going to paste in the test program I wrote to ensure that it's broken in
> general (and not just in my project) as well as a backtrace after running it
> through GDB and making it produce the bus error as this information is
> probably useful.
>
> Some notes about the code: currently it just looks for the directory
> "hello." I also tried nesting directories in the form of "hello/foo." If foo
> did not exist, the program worked fine. If foo did exist, but was not a
> directory, the program ran fine. If foo existed and was a directory, we get
> the bus error. The same symptoms happen when searching for normal files
> using the attribute of "~FA_DIREC" (anything but a directory)
>
>
> Running PPC Mac OS X 10.4.6. I did a fresh update/depend/make/install/etc.
> If you need any more information, let me know
>
> -Jay
>
> CODE:
> ---
> #include <allegro.h>
>
> int main()
> {
>         allegro_init();
>         if(file_exists("hello", FA_DIREC, NULL) == 0)
>         {
>                 fprintf(stderr, "The directory doesn't exist!\n");
>         }
>         else
>         {
>                 printf("Directory found!\n");
>         }
>         return 0;
> }
> END_OF_MAIN()
> ---
>
> GDB Backtrace:
> ---
> (gdb) file a.out
> Reading symbols for shared libraries .... done
> Reading symbols from /Users/jay/Desktop/test/a.out...done.
> (gdb) run
> Starting program: /Users/jay/Desktop/test/a.out
> Reading symbols for shared libraries
> ................................................................................
> done
>
> Program received signal EXC_BAD_ACCESS, Could not access memory.
> Reason: KERN_PROTECTION_FAILURE at address: 0x00000020
> [Switching to process 3641 thread 0x3503]
> 0x900017dc in pthread_mutex_lock ()
> (gdb) backtrace
> #0  0x900017dc in pthread_mutex_lock ()
> #1  0x9001b258 in closedir ()
> #2  0x300cc0ac in al_findclose ()
> #3  0x30027fb4 in file_exists ()
> #4  0x00002a70 in _mangled_main ()
> #5  0x00002f8c in call_user_main ()
> #6  0x00002fcc in +[AllegroAppDelegate app_main:] ()
> #7  0x92976194 in forkThreadForFunction ()
> #8  0x9002ba68 in _pthread_body ()
>
>
> --
> https://lists.sourceforge.net/lists/listinfo/alleg-developers
Index: src/unix/ufile.c
===================================================================
--- src/unix/ufile.c	(revision 5817)
+++ src/unix/ufile.c	(working copy)
@@ -468,7 +468,9 @@
    struct FF_DATA *ff_data = (struct FF_DATA *) info->ff_data;
 
    if (ff_data) {
-      closedir(ff_data->dir);
+      if (ff_data->dir) {
+         closedir(ff_data->dir);
+      }
       _AL_FREE(ff_data);
       info->ff_data = NULL;