Thread: free(something) after RETURN

Let's say I have the following:

Code:

char *sendBack(char *someText)
{
     char *newText = malloc( sizeof(*newText));
     ...
     ...
     ...
     return(newText);
     free(newText);     // will never get reached here
     newText = NULL;     // will never get reached here
}

As you can see, I need to "return" something and then free it once I'm done with it. My question is: Since I can't free it here in the sendBack function, can I free it in the calling function? For example, is this legal?:

Code:

void printMe()
{
     char buf[100];
     buf = sendBack("blah blah blah");
     printf("%s\r\n", buf);

     free(buf);     // is this freeing *newText?
     buf = 0;
}

Something just doesn't look right.

Any suggestions?

Originally Posted by matsp

Yes, freeing in the calling function is exactly what you SHOULD do in this case.

Obviusly, putting code after an unconditional return is only ever going to possibly give you a warning for "unreachable code" if the compiler supports that - but it will never be RUN, so you can delete those two lines straight away.

--
Mats

Excellent, thank you. I wasn't sure if freeing buf in the calling function would free what I needed freed.

Thank you for clarifying.

Originally Posted by QuantumPete

I guess you meant:

Code:

char *newText = malloc (strlen (*someText));

With a "+ 1" probably?

Originally Posted by QuantumPete

Code:

char *sendBack(char *someText)
{
     char *newText = malloc( sizeof(*newText));

I guess you meant:

Code:

char *newText = malloc (strlen (*someText));

Or else you'll get the sizeof the thing being pointed to by newText and that's just a char.

As well as being able to free the memory in the calling function, you could also allocate the memory in the calling function and then pass the pointer. This may not always be suitable, but as a rule of thumb the function/object that allocates memory should free it too.

QuantumPete

Again, thanks for the insight. And thank you for the correction on the malloc, you're correct.

Originally Posted by QuantumPete

Code:

char *sendBack(char *someText)
{
     char *newText = malloc( sizeof(*newText));

I guess you meant:

Code:

char *newText = malloc (strlen (*someText));

Or else you'll get the sizeof the thing being pointed to by newText and that's just a char.

As well as being able to free the memory in the calling function, you could also allocate the memory in the calling function and then pass the pointer. This may not always be suitable, but as a rule of thumb the function/object that allocates memory should free it too.

QuantumPete

Since we're all correcting each other - he'll most likely get 4 bytes, eg the size of a pointer.

Do you really need to dynamically allocate the newtext?