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    <p>I wouldn't. If your program crashes, because of some exotic, unforeseen things that happen in your program, it might even be pointless to try and free any allocated heap memory.<br/> I think it'd be best if you just call <code>exit (EXIT_FAILURE)</code>, if you can, and leave the OS to reclaim the memory you allocated as good as it possibly can.</p> <p>However, I would try to clean up any <em>other</em> resources that you've used/claimed/opened that may also cause leak. Close as many opened file pointers as you can, or flush any buffers lying around.<br/> Other than that, I'd say: leave it to the OS. Your program has crashed, or is crashing: trying to clean up after yourself in an unforeseen situation might be pointless, or -who knows- eventually do more harm than good.</p> <p>Of course, if by <em>"a library errors"</em> you mean something like:</p> <pre><code>MYSQL *connection = mysql_init(); if (connection == NULL) {//connection could not be initiated //what to do here? } </code></pre> <p>Or, no lib:</p> <pre><code>char **arr_of_strings = malloc(200*sizeof(char *)); //some code arr_of_strings[0] = calloc(150, sizeof(char)); //some more arr_of_strings[120] = calloc(350, sizeof(char)); if (arr_of_strings == NULL) {//ran out of heap memory //what do I do here? } </code></pre> <p>So, basically: it's a matter of: What does your program have to <em>do</em>, and can you easily find a way around the problems you're being faced with.<br/> If, for example, you're writing a mysql client, and the <code>mysql_init</code> call fails, I think it pretty evident you <em>cannot</em> continue. You could try to provide a fallback for every reason why this could happen, or you could just exit. I'd opt for the latter.<Br/> In the second case, it's pretty clear that you've depleted the heap memory. If you're going to write these strings to a file anyway, you could prevent this kind of error like so:</p> <pre><code>int main() { char **arr_str = malloc(20*sizeof(char *)); const char *fileName = "output.txt"; int i, j; int alloc_str(char ***str, int offset, int size); void write_to_file(const char *string, const char *fileName); for(i=0;i&lt;10;++i) { if (alloc_str(&amp;arr_str, i, 100+i) == -1) { if (i == 0) exit(EXIT_FAILURE);//this is a bigger problem for (j=0;i&lt;i;++j) {//write what we have to file, and free the memory if (arr_str[j] != NULL) { write_to_file(arr_str[j], fileName); free(arr_str[j]); arr_str[j] = NULL; } if (alloc_str(&amp;arr_str, i, 100+i) != -1) break;//enough memory freed! } } //assign value to arr_str[i] } for(i=0;i&lt;10;++i) free(arr_str[i]); free(arr_str); return 0; } void write_to_file(const char *string, const char *fileName) {//woefully inefficient, but you get the idea FILE* outFile = fopen(fileName, "a"); if (outFile == NULL) exit (EXIT_FAILURE); fprintf(outFile, "%s\n", string); fclose(outFile); } int alloc_str(char ***str, int offset, int size) { (*str)[offset] = calloc(size, sizeof(char)); if ((*str)[offset] == NULL) return -1; return 0; } </code></pre> <p>Here, I'm attempting to create an array of strings, but when I run out of memory, I'll just write some of the strings to a file, deallocate the memory they take up, and carry on. I could then refer back to the file to which I wrote the strings I had to clear from memory. In this case, I can ensure, though it does cause some additional overhead, my program will run just fine.<br/> In the second case, freeing memory is a must, though. I <em>have</em> to free up the memory required for my program to continue running, but all things considered, it's an easy fixed.</p>
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    1. CO+1 about "other resources".
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