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POrealloc fails after multiple calls only when not debugging
 

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  1. POrealloc fails after multiple calls only when not debugging
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    <p>The below code occasionally fails on the <code>buffer = (char*) realloc(buffer, allocated * sizeof(char));</code> call (marked down below) that I use to dynamically allocate space for a <code>char*</code>,by allocating 1 char initially, and doubling the allocated amount every time the memory I already have is insufficient to store the string. </p> <p>I have very similar code in many other parts of my project, with the same memory allocation policy and calls (changing only the type of the <code>void*</code> I pass to <code>realloc</code>). </p> <p>I am using VS2010 to debug the problem, and when I start the program on debug mode, the function always completes successfully. </p> <p>However, when calling the program from the command line, there is a good chance that one of the calls to realloc will fail after some time with an "Access violation reading location" error - though it doesn't happen all the time, and only happens after the function below has been called multiple times, with many reallocations having already taken place. </p> <p>What's weirder, I put some prints before and after the realloc call to assert if the pointer location was changed, and, when I did so and ran the program, the calls to realloc stopped failing randomly.</p> <p>What am I doing wrong?</p> <pre><code>TOKEN next_token_file(FILE* file, STATE_MACHINE* sm, STATE_MACHINE* wsssm) { char* buffer = (char*) malloc(sizeof(char)); size_t allocated = 1; size_t i = 0; while(1) { /* ... code that increments i by one and messes with sm a bit. Does nothing to the buffer. */ // XXX: This fails when using realloc. Why? if(i + 1 &gt;= allocated) { allocated = allocated &lt;&lt; 1; buffer = (char*) realloc(buffer, allocated * sizeof(char)); } buffer[i] = sm-&gt;current_state-&gt;state; /* ... more code that doesn't concern the buffer */ } // Null-terminate string. buffer[++i] = 0; TOKEN t = {ret, buffer}; return t; } </code></pre>
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    1. USRenan Gemignani
    1. USRenan Gemignani
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      1. VTUpMod
    1. COShouldn't this `size_t allocated = 1;` be `size_t allocated = 16;`?
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      1. USalk
    2. COThat'd be my guess, either that or he really does want to go from 16 chars down to 2 on the first round (which would be ... strange).
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      1. USWhozCraig
 

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