Re: [Dev-C++] Allocation problem

[Per W. <pw...@ia...>]

prj_info.input is a pointer to a pointer to char.

If you want to store 10 lines in it:

info.input = (char**)malloc(10*sizeof(char*));
info.input[0] = (char*)malloc(sizeof(char)*(strlen("mystr1")+1));
...
info.input[9] = (char*)malloc(sizeof(char)*(strlen("mystr10")+1));

strcpy(info.input[0],"mystr1");
...
strcpy(info.input[9],"mystr10");

Question: Don't you ever try to get the compiler to generate as many
warnings as possible, and then check up on the warnings?

The compiler would definitely become a bit worried when you do:
  info.input = (char*)malloc(...);
since you are typecasting to the wrong type.

Take two steps back and think a bit about your code and what you want to
do. Check up on all data types, and exactly what you allocate.

That little realloc() line you have is very, very interesting. You are
reallocating the wrong thing - did you intend to reallocate the array
of pointers to text strings, or a specific string buffer in the array?
- and you are forgetting that the new pointer is the RETURN VALUE of the
realloc() call.

/Per W

On Sat, 20 Sep 2003, Matthews wrote:

> Still giving me the same crash :\
>
> At 11:32 AM 20/09/2003 +0200, Per Westermark wrote:
> >When you allocate buffers for strings, you must allocate room for
> >strlen(str)+1
> >characters, or the termination character '\0' will not fit.
> >
> >/Per W
> >
> >On Fri, 19 Sep 2003, Matthews wrote:
> >
> >> I'm working on a program to generate makefiles for me, and I currently have
> >> it set up to read different sections of a file to generate the options.
> >> One section is %input, which has a list of filenames to include, eg.
> >>
> >> prj.txt
> >>
> >> %input
> >> main.c
> >> vid.c
> >> gui.c
> >>
> >> I read these into a struct organized like so:
> >>
> >> struct prj_info
> >> {
> >>   ...
> >>   char **input;
> >>   ...
> >> }
> >>
> >> And I allocate space based on how many files there are (an array of
> >> strings, basically)
> >>
> >> My problem is that I get errors when running the following C code:
> >>
> >> if(!strncmp("%include",t,strlen(t)-1))
> >> {
> >>   count = 0;
> >>   skip_line(buf);
> >>   getword(buf,t);
> >>   longest_length = strlen(t);
> >>   info.input = (char *)malloc((sizeof(char)*longest_len)*1);
> >>   if(!info.input)
> >>   {
> >>     printf("OH NOS\n");
> >>     return 0;
> >>   }
> >>   //CRASH HERE
> >>   strcpy(info.input[count],t);
> >>   while(*buf!='%')
> >>   {
> >>     while(*buf=='#'||isspace(*buf)) skip_line(buf);
> >>     getword(buf,t);
> >>     if(strlen(t)>longest_length) longest_length = strlen(t);
> >>     count++;
> >>     realloc(info.input,(sizeof(char)*longest_length)*count);
> >>     if(!info.input)
> >>     {
> >> 	printf("ERR0RZ\n");
> >> 	return 0;
> >>     }
> >>     strcpy(info.input[count],t);
> >>     skip_line(buf);
> >>   }
> >> }
> >>
> >> Buf is the dumped contents of a file (like prj.txt), getword() places a
> >> word from buf into t and skip_line() skips to the next line in buf.
> >>
> >> The code compiles fine, but crashes at the first strcpy().  Any help would
> >> be appreciated.
> >>
> >>
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