Question

I have a function prototype which provides me with the result I’m after:

#include <stdio.h>
#include <string.h>

int main ()
{
  char * pch;
  char str[] = " 81.243.230.174, 10.1.0.102";
  pch = (char*) memchr (str, ',', strlen(str));
  char * tch;
  memcpy (tch, str, pch-str);
  if (pch!=NULL){
    printf ("',' found at position %ld.\n", pch-str);
    printf ("XFF: %s\n", tch);
  } else {
    printf ("',' not found.\n");
  }
  return 0;
}

Returns the following:
$>’,’ found at position 15.
$>XFF: 81.243.230.174

I want to process the output of VRT_GetHdr from libvcl as str above, as follows:

char * pch;
char str[] = VRT_GetHdr(sp, HDR_REQ, "\023X-FF:");
pch = (char*) memchr (str, ',', strlen(str));
char * xff;
memcpy (xff, str, pch-str);

    if (get_country_code)
            VRT_SetHdr(sp, HDR_REQ, "\017X-Country-Code:", (*get_country_code)(xff), vrt_magic_string_end);

VRT_GetHdr returns a char pointer and the compiler complains about an “invalid initializer.”

If I change the assignment of
char str[]
to
char *str
, varnish dies at runtime (probably with a segfault).
How can I get the expected result from my inline C, without using the above pointer to array mess?

Answer 1

You can’t.

The initializer expression must be literal to provide a compile-time size, and your function call isn’t.

You might be able to get around this using C99’s automatic arrays, but it’s maybe easier and cleaner to just use a dynamically allocated array (using malloc(), or strdup() if you have it).

Or even a static limit that is “large enough”, if you have reason to believe there is some limit to the length of the return value.

Your code reads a bit like a re-implementation of strtok(), perhaps you can use it directly?