[Crossfire-wiki] [Crossfire DokuWiki] page changed: user:mhoram:code:bwp

[no-reply_wiki at metalforge.org]

A page in your DokuWiki was added or changed. Here are the details:

Date        : 2007/01/17 11:54
User        : mhoram
Edit Summary: thanks for the help

@@ -1,15 +1,34 @@
  ====== Build Wiki Pages ======
  
  This is a program I'm working on to automate the building of pages for the wiki from the monster archetypes (and eventually other categories, perhaps).  I'm still working on it, but I thought I'd put it here in case anyone wanted to help me fix a problem I'm having, or critique my code.  (I'm still very much an amateur at writing C.)
  
- The main problem I'm having right now is that a couple variables are getting clobbered; I assume by bad memory allocation.  It happens at line 502: the variables *key[] and *val[] are fine before that call to join_with_comma(), but after it they are messed up.  (Search for BEFORE and AFTER.)  Since they aren't involved in that function at all, I assume that something in that function is causing an overflow.  There's probably a way with gdb or some other tool to see what variable is using a particular memory address, but I don't know what it is. 
+ The main problem I'm having right now is that a couple variables are getting clobbered; I assume by bad memory allocation.  It happens at line 502: the variables ''*key[]'' and ''*val[]'' are fine before that call to ''join_with_comma(),'' but after it they are messed up.  (Search for ''BEFORE'' and ''AFTER''.)  Since they aren't involved in that function at all, I assume that something in that function is causing an overflow.  There's probably a way with gdb or some other tool to see what variable is using a particular memory address, but I don't know what it is. 
  
  Also, if anyone knows of a good C primer/tutorial online, please let me know.
  
    * In the sortbyname, a and b will be const char* *, not char*, thus you need to dereference them => ''strcpy(aa,(*(const char* *)a));'' or something like that :)
      * I've stared at this for a while, and found some examples that do it, and I think I'm starting to understand it.  I still don't quite see how the arguments can be char* *, when the function defines them as const void *, but I'll get there.
-       * I changed it to the example you gave, and now it segfaults on that strcpy. ;-)  I think I'm on the right track now, though.  It makes sense that the problem was in that comparison routine, since I checked the addresses of the variables within join_with_comma, and none of them were even close to the ones that were getting mangled.
+       * I changed it to the example you gave, and now it segfaults on that ''strcpy''. ;-)  I think I'm on the right track now, though.  It makes sense that the problem was in that comparison routine, since I checked the addresses of the variables within ''join_with_comma'', and none of them were even close to the ones that were getting mangled.
+     * Ok, I've updated the code below to reflect those changes, but I'm still having trouble in ''sortbyname''.  All the examples I can find online do it like you suggested, or something similar, but when I do that, I get strange results.  Here's what gdb says about the first argument:
+ 
+ <code>
+ Breakpoint 1, sortbyname (a=0xbfbbffd0, b=0xbfbc09d0) at bwp.c:259
+ 259         return strcasecmp( *(char **)a, *(char **)b );
+ (gdb) p a
+ $1 = (const void *) 0xbfbbffd0
+ (gdb) p (char **)a
+ $2 = (char **) 0xbfbbffd0
+ (gdb) p (char *)a
+ $3 = 0xbfbbffd0 "Gnarg"
+ (gdb) p *(char *)a
+ $4 = 71 'G'
+ (gdb) p *(char **)a
+ $5 = 0x72616e47 <Error reading address 0x72616e47: Bad address>
+ </code>
+ 
+ The way I read that, it looks like what I really want to pass to ''strcasecmp'' is a pointer to ''(char *)a'', but that doesn't work either.  (You can see that attempt commented out.)  I think for today I'm just going to comment out the ''qsort'' call so I can finish the rest of the program; in the meantime, any further hints on what I'm doing wrong would be much appreciated.
+ 
  
    * Also, to compare, try ''strcasecmp'' which does case-insensitive comparison.
      * That would be much easier, wouldn't it? :-)
  


IP-Address  : 206.71.197.56
Old Revision: http://wiki.metalforge.net/doku.php/user:mhoram:code:bwp?rev=1169055870
New Revision: http://wiki.metalforge.net/doku.php/user:mhoram:code:bwp

-- 
This mail was generated by DokuWiki at
http://wiki.metalforge.net/