Freeing an array of character pointers (string literals)?

Question

I'm trying to figure out how to free the memory for an array of character pointers (string literals), but I can't quite get the syntax. This is how I'm declaring and initializing the arrays.

char * words[] = { "THESE", "ARE", "SOME", "WORDS" };

I've tried doing this...

free(words);

And this...

for(i = 0; i < 4; i++) {
    free(words[i]);
}

But the first one causes some sort of invalid pointer error with glibc, and the second one causes a segmentation fault.

So what's the right way to free this memory?

This is a statically initialized array. You shouldn't be freeing it anyway. — Mike Holt
– Mike Holt, Commented May 2, 2014 at 0:07
"what's the right way"? Do nothing. It's freed automatically. — lethal-guitar
– lethal-guitar, Commented May 6, 2014 at 21:07

Casper Beyer · Accepted Answer · 2014-05-04 19:47:09Z

3

If you did not allocate it (e.g malloc, calloc) then you shouldn't be deallocating it either (e.g free).

Documentation will in general be very clear and explicit if you need to free a pointer returned from a function, for example strdup would be such a case.

edited May 4, 2014 at 19:47

answered May 2, 2014 at 0:10

Casper Beyer

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4 Comments

Darin Beaudreau Over a year ago

Ah, alright. I ask because I have some memory leaks in my program and it looked like those arrays had the right number of elements to be the culprit. Guess I get to have more fun with my vector and string libraries...

Casper Beyer Over a year ago

Try debugging with valgrind.

Kerrek SB Over a year ago

@DarinBeaudreau: Don't program by random guessing. Learn the rules of the language and follow them.

M.M Over a year ago

This is true in Standard C. In POSIX and compiler extensions, sometimes you find functions that return memory you must free() despite the fact that you didn't malloc it. For example, strdup and getline.

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