kashyap garimella wrote at 2009-09-12: > Greetings! > > I have added the following new features: > > 1) when grub-setup runs, it automatically stores the areas of (mbr + embed) > region, which are overwritten, into the file (in the following specified > format) in root directory. > > 2) grub-setup can restore the stored mbr in the following format back to > destination drive: > [...] > > PROBLEMS: > A warning: > util/i386/pc/grub-setup.c:93: warning: ‘backup_img’ may be used > uninitialized in this function > When I remove the line (496 in the patched one): free(backup_img); > the warning goes off. > I could not understand how to resolve it. I need some help
I looked at the patch and it seems that the problem could be caused by
following code:
> + if (!backup_fp)
> + {
> + strcpy(grub_errmsg,"Unable to create the backup file");
> + goto unable_to_save;
> + }
> +
> + /* 8 bytes for embed_region.start, another 8 for core_size */
> + int backup_img_size = core_size + GRUB_DISK_SECTOR_SIZE + 8 + 8 + 1 /*
> seperation byte 0xff */ ;
> + backup_img = (char *) xmalloc (backup_img_size);
...
> +save_finish:
> + fclose (backup_fp);
> + free(backup_path);
> + free(backup_img);
Notice that you're using "goto" to skip initialization of backup_img and
you blindly free()ing it in "save_finish".
I think a nice way to fix this (if you want to use "goto") is to use
multiple clean up labels. Like this:
+save_cleanup_backup_img:
+ free(backup_img);
+save_cleanup_backup_fp:
+ fclose (backup_fp);
+save_cleanup_backup_path:
+ free(backup_path);
Note that you should release the resources in reverse order compared to
the order of acquiring the resources. If you need to bail out after you
have acquired the backup_fp but have not yet acquired the backup_img,
use "goto save_cleanup_backup_fp".
--
Mikko
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