Another simple C string question

MicahCarrick · 01-14-2007, 04:17 PM

Not really sure how the compiler handles this. Let's say a function returns a newly allocated string. If you use the function as a parameter to another function, how would you free the returned string? You couldn't... right?

ie:

Code:

char* str1 = "Some string";
/* ... */
printf ("string: %s", strdup(str));
/* what happens to the string returned by strdup? */

Dan04 · 01-14-2007, 04:42 PM

Not easily. Try using a temporary variable:

Code:

strTemp = strdup(str);
printf("string: %s", strTemp);
free(strTemp);

(Of course, because printf doesn't modify its arguments (unless "%n" is used), there's no point in calling strdup there.)

PTrenholme · 01-14-2007, 05:06 PM

Dan04, did you perhaps mean:

Code:

strTemp = strdup(str);
printf("string: %s", strtTemp);
free(strTemp);

Unless I misunderstand something (which is, of course, quite possible) your suggestion doesn't actually free the memory used in the call.

MicahCarrick · 01-14-2007, 05:33 PM

That's what I was thinking... but I see this done from time to time. My original posting would be a memory leak then, correct?

Dan04 · 01-14-2007, 09:03 PM

Quote:

Originally Posted by PTrenholme

Dan04, did you perhaps mean:

Code:

strTemp = strdup(str);
printf("string: %s", strtTemp);
free(strTemp);

Yes. Thanks for noticing.

KenJennings · 01-16-2007, 01:35 PM

Quote:

Originally Posted by MicahCarrick

That's what I was thinking... but I see this done from time to time. My original posting would be a memory leak then, correct?

Yes, it is a memory leak. Wherever you see it done spank (politely correct

) the developer responsible.