functions returning a string or other buffer: need to free it?

**Nyda** · 07-10-2004

I'm wondering if I generally have to free a string/buffer returned by a function if the documentation doesn't mention this.

In case of i.e g_strdup() the documentation mentions that I should free the returned buffer but then there are also functions like inet_ntoa() where the documentation doesn't say anything about this.

I'm also wondering what happens if I use such a function in the parameterlist of another function without ever storing a pointer in my code. Is that memory lost or is there a mechanism in place to handle this?

**Sebastiani** · 07-10-2004

no, you generally won't need to free the data in those cases - it's global data managed by the C-runtime environment. but you SHOULD copy the data immediately and not store pointers to it. there may also be some issues when using those functions in multithreaded applications - read the documentation to be certain.

**quzah** · 07-11-2004

Code:

char *freemymemory( void )
{
    char *s = malloc( sizeof( "Hello World!" ) );
    strcpy( s, "Hello World!" );
    return s;
}

char *donotfreeme( void )
{
    static char buf[BUFSIZ] = "Hello World!";
    return buf;
}

Quzah.

**Nyda** · 07-11-2004

Originally Posted by quzah

char *donotfreeme( void )
{
static char buf[BUFSIZ] = "Hello World!";
return buf;
}
[/code]

The problem is that I can't look into someone elses' function. Btw, the example would not work without use of static, right?

**Sebastiani** · 07-11-2004

>> Btw, the example would not work without use of static, right?

right.

**Emmanuel Delaha** · 07-11-2004

Originally Posted by Nyda

The problem is that I can't look into someone elses' function.

This is why it should be mentionned in the documentation. If you have no doc, the only hope is some smart comment in the header file where the prototype is defined... If not, all bets are off.

Btw, the example would not work without use of static, right?

Correct.

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