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POC - Unexpected Segmentation Fault on strtok(...)
 

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  1. POC - Unexpected Segmentation Fault on strtok(...)
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    <p>I am using strtok(...) of the library and it appears to be working fine until the end condition, where it results in a segmentation fault and program crash. The API claims that strtok(...) will output a NULL when there are no more tokens to be found, which meant, I thought, that you had to catch this NULL in order to terminate any loops that you were running using strtok(...). What do I need to do to catch this NULL to prevent my program from crashing? I imagined the NULL was allowed for use as a terminating condition.</p> <p>I have prepared a SSCCE for you to observe this behavior. I need strtok(...) to work for a much larger piece of software I am writing, and I am getting the exact same segmentation behavior. The output at the command line is shown below this code vignette (yes I know you use &lt;...> to enclose libraries, but I was having difficulty getting this post to display the code libraries). I am using gcc version 4.5.3, on a Windows 8 OS, and below shows two different flavors of how I imagine one could try to catch the NULL in a loop.</p> <pre><code>#include &lt;stdlib.h&gt; #include &lt;stdio.h&gt; #include &lt;unistd.h&gt; #include &lt;sys/types.h&gt; #include &lt;sys/stat.h&gt; #include &lt;fcntl.h&gt; #include &lt;string.h&gt; main(){ char* from = "12.34.56.78"; char * ch = "."; char * token = strtok(from, ch); printf("%s\n",token); while(token != NULL){ token = strtok(NULL, ch); printf("%s\n", token); } printf("Broke out of loop!"); while(strcmp(token, 0) != 0){ printf("%s\n",token); token = strtok(NULL, ch); } } </code></pre> <pre> ############ OUTPUT: ############ $ ./test 12 34 56 78 Segmentation fault (core dumped) </pre>
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    1. US9codeMan9
    1. US9codeMan9
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      1. POC - Unexpected Segmentation Fault on strtok(...)
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      1. VTUpMod
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      1. USBarath Ravikumar
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    1. COIt's never really unexpected when `strtok` segfaults. It should only be used in conjunction with `gets` (which is to say, never!)
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      1. USWilliam Pursell
    2. CO`strcmp(NULL,0)` <- boom!
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      1. POC - Unexpected Segmentation Fault on strtok(...)
      1. USAniket Inge
    3. COAniket may be right but I never make it to the second loop (I edited the above vignette to reflect this--the output is still the same). @WilliamPursell would you standardly use it with gets(...)? Are you saying that we can never use strtok b/c it's a broken method? What is it even good for? I really like its tokenizing ability, otherwise, my code that was written around it will ballloon ten-fold
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