my strstr is broken

Allin Cottrell cottrell@wfu.edu
Tue Sep 11 12:58:00 GMT 2018


On Tue, 11 Sep 2018, Michael Brunnbauer wrote:

> hi all,
>
> I assume it cannot be reproduced and is limited to my build?
>
> Any ideas/hints for me? The fact that the needle is 513 bytes and occurs at
> an offset of 513 bytes in the haystack should provide some clue?
>
> cu,
> brunni
>
> On Mon, Sep 10, 2018 at 04:47:52PM +0200, Michael Brunnbauer wrote:
>>
>> can someone reproduce this with 2.28 (program exits with return code 255)?
>>
>> -----------------------------------------------------------
>> #include <string.h>
>>
>> int main (void)
>> {
>>  char* i = "                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx";
>>  char* n = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx";
>>  if (!strstr(i,n)) return 255;
>>  return 0;
>> }

Since it's difficult to verify your long strings in email I tried the 
following variant of your test:

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

int main (void)
{
     char h[513*2+1];
     char n[513+1];
     char *s;
     int i;

     for (i=0; i<513; i++) {
         n[i] = 'x';
         h[i] = ' ';
         h[i+513] = 'x';
     }
     n[513] = '\0';
     h[513*2] = '\0';

     printf("h=\"%s\"\n", h);
     printf("n=\"%s\"\n", n);
     s = strstr(h, n);
     printf("s = %p\n", (void *) s);
     printf("strcmp(n, s) = %d\n", strcmp(s, n));

     return 0;
}

Compiled with gcc 8.2.1 20180831 (Arch) the output is

s = 0x7ffe8771ae51
strcmp(n, s) = 0

--
Allin Cottrell
Department of Economics
Wake Forest University, NC


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