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POSegmentation fault in C, can't seem to find the cause
 

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  1. POSegmentation fault in C, can't seem to find the cause
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    <p>I can't seem to find the cause of the segmentation fault in the code below. The code crashes in the line with the comment, after jumping back to main() from evaluate(). I looked at this code with gdb, and it seems everything is ok within the evaluate function - Output is filled in correctly, however after I return to main, nothing in the memory can be accessed. "p j" in gdb return an memory not accessible error, as does trying to print any other variable. I checked if the stack maybe had to many values, but increasing the stack size does not help.</p> <p>The crazy thing is that I can solve this error, but I have no idea why it changes anything. If I add, anywhere in evaluate(), an int declaration (eg. <code>int iAmNotUsedEver;</code>) then the code suddenly doesn't cause a segmentation error and works perfectly in gdb. Edit: Dynamically allocating node[116] in evaluate (<code>int *node = malloc(116*sizeof(int));</code>) also resolves the issue, but again I have no idea why?</p> <p>Evaluate function: (I removed part of the code, otherwise it would be way too long)</p> <pre><code>void evaluate(int *parameter, int output[][16]) { int node[116]; node[0] = 0; output[0][0] = !node[0]; node[1] = parameter[0]; output[0][1] = !node[1]; output[0][2] = !node[0]; ... node[34] = !node[114] &amp;&amp; !node[45]; node[45] = !node[34] &amp;&amp; !node[105]; output[11][15] = node[45]; } </code></pre> <p>Main function:</p> <pre><code>int main(int argc, char *argv[]) { int i; int j; int k; int ret; int parameter[8]; int output[12][16]; FILE *paramFile; FILE *outFile; paramFile = fopen(argv[1], "r"); if (paramFile == NULL) { printf("I couldn't open the parameter file.\n"); exit(0); } outFile = fopen(argv[2], "ab"); if (outFile == NULL) { printf("Something went wrong with the output file.\n"); exit(0); } while(1){ for(i=0;i&lt;8;i++){ ret=fscanf(paramFile, "%d", &amp;parameter[i]); printf("parameter: %d\n", parameter[i]); } if(ret!=1){ break; } for(j=0;j&lt;12;j++){ for(k=0;k&lt;16;k++){ output[j][k] = 2; } } evaluate(parameter,output); printf("Evaluation is done. \t %d\n",i); for(j=0;j&lt;12;j++){ //SEG FAULT HERE for(k=0;k&lt;16;k++){ fprintf(outFile, "%d", output[j][k]); } fprintf(outFile,"\n"); } fprintf(outFile,"\n\n\n"); } printf("Closing files\n"); fclose(paramFile); fclose(outFile); return 0; } </code></pre>
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    1. USCassiel
    1. USCassiel
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    1. CO116 nodes, 116+ outputs :D this is confusing.... I'd think about the naming (this doesn't fix the prob but would make this way easier to follow)
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      1. POSegmentation fault in C, can't seem to find the cause
      1. USDaij-Djan
    2. COYou should strongly consider using Valgrind to track buffer overflow problems.
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      1. POSegmentation fault in C, can't seem to find the cause
      1. USOliver Charlesworth
    3. COis output[12][16] of int type in your code or did you just use int for simplicity in your question? If output is of pointer-to-something type then the issue would be that in evaluate(), node[] is allocated in the stack and doing output[i][j] = node[x] will assign pointers to stuff that goes out of scope.
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      1. POSegmentation fault in C, can't seem to find the cause
      1. USnairdaen
 

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