Wrapping a C library

[Graham J Lee]

Hi,

I'm creating a wrapper class for libdict (yes, I realise this has 
possibly been done before), and running into a segfault problem.  I 
realise this has possibly more to do with bad C than with Foundation 
per se, but I'd appreciate some help :-)

libdict has a function ld_define, declared thus in libdict.h:
struct ld_defanswer **ld_define(struct ld_conn *conn, char *word);

and I have an object GLDictionaryAccessor which contains the following 
method:
-(struct ld_defanswer **)define:(NSString *)w
{
        return ld_define(connection,[w cString]);
}

I wrote an ObjC CLI interface for the class [this is, apart from for 
testing purposes a bit pointless, as I fgets c strings, 
stringWithCString them, then use cString in the wrapper object...] 
which does this:

                if(!strcasecmp(input,"define"))
                {
                        struct ld_defanswer **d;
                        printf("Define word: ");
                        fgets(arg1,BUFSIZ,stdin);
                        arg1[strlen(arg1)-1]='\0';
                        a1=[NSString stringWithCString:arg1];
                        d=[da define:a1];
                        if(d==NULL)
                        {
                                printf("No results for '%s'\n",arg1);
                        }
                        else
                        {
                                while(d[i]!=NULL)
                                {
                                        printf("Got HERE too, d[i]=%d\n",d[i]);
                                        printf("Found 
definition:\n%s\n",d[i]->ld_ansdef);
                                        i++;
                                }
                        }
                        continue;
                }

which looks, to me at least, the same as the code in a C CLI interface 
for the library, which does this:
        struct ld_defanswer **ans;
        int i = 0;

        if(!(ans = ld_define(conn, arg))) {
                printf("No results for '%s'.\n", arg);
        } else {
                while(ans[i]) {
                        printf("Found in dictionary '%s':\n", 
ans[i]->ld_ansdict);
                        printf("%s\n", ans[i]->ld_ansdef);
                        i++;
                }
        }

except that mine segfaults and theirs doesn't :-(.  gdb doesn't offer 
much information:
dictstep> define
Define word: foo
Got HERE too, d[i]=1851596885

Program received signal EXC_BAD_ACCESS, Could not access memory.
0x000032bc in main (argc=1, argv=0xbffffb58) at dictstep.m:169
169                                             printf("Found 
definition %s:\n",d[i]->ld_ansdef);
(gdb) bt
#0  0x000032bc in main (argc=1, argv=0xbffffb58) at dictstep.m:169
(gdb) quit

I am lost.

Cheers,

Graham.
--
Graham Lee                       GPG Key ID: 01D5B9D8
UNIX Systems Manager,
Oxford Physics Practical Course
http://nextstep.sdf-eu.org               01865 273450