[SOLVED] Not able to return pointer from C function

retroCheck · 02-13-2015, 05:47 PM

I have allocated the memory for given variable and still not able to return a pointer. Not sure what I am doing wrong here. Any help would be great, thanks.

Code:

char * getRdir(char* arg) {
		char *dirptr = (char *) malloc(sizeof(2));
		char *cmpl = "<";
		char *cmpll = "<<";
		char *cmpr = ">";
		char *cmprr = ">>";
	if (strcmp(arg, cmpl) == 0) {
		dirptr = "<";
		printf("%s%c\n", "This is a dir - ", *dirptr);
	}else if(strcmp(arg,cmpll)){

	}
	return dirptr;
}

retroCheck · 02-13-2015, 05:55 PM

Durp, after struggling for this for awhile I come to find out that I had a void return from where I was declaring the function. It works fine now.

Keith Hedger · 02-13-2015, 05:59 PM

You are correctly creating your ptr with maloc but then you assign the pointer to a constant string 'dirptr="<" you would be best dropping the malloc and use strdup to assign the ppointer and set the data, or one of the other string assignment functions.
also drop the sizeof out of the malloc, sizeof returns the storage size of a variable etc, so you should just use 'malloc(2)'
You would be best setting the variable dirptr to NULL before doing any assignments that way on return from the function you can test for a NULL ptr anf if true the assignment faiked and yiu can take appropriate steps

ntubski · 02-13-2015, 06:04 PM

Quote:

Originally Posted by retroCheck

I have allocated the memory for given variable and still not able to return a pointer.

You don't really explain what "not able" means, are you getting a compile error, a segfault, or...?

Code:

		char *dirptr = (char *) malloc(sizeof(2));

I think you meant 2, not sizeof(2). Though you might need to 3 for the nul terminator if you intend to store "<<" there.

Code:

		dirptr = "<";

You're overwriting the pointer you got from malloc() here, so this is a memory leak. You probably want something like strcpy(dirptr, "<"); Or use strdup() like Keith Hedger suggests.

mina86 · 02-13-2015, 06:22 PM

What's wrong with casting malloc's return value?

Also, strdup is non-standard so keep that in mind if you want your program to be super-portable.

retroCheck · 02-13-2015, 06:33 PM

I see now that little bit of code although able to compile still has issues. Thanks for the advice. I did end up using strdup(not concerned with portability).

What I mean by "not able" was that I was getting a "no new declaration..." error. This was because of not having the right return value at the function declaration. Oh did not see that memory leak, thanks.