Thread: HELP: Function returning char *

Hello,

I need a function in C that accepts some const arguments, and return a string (a char *). In my functions, I get memory fault error at execution time.

Could you please provide me with a small sample function, and its invokation?

Thanks

Post your code so we can take a look at it.

Ok here an example:

Code:

char *mystrcat(char *dest, const char *src1, const char *src2)
{
	char *tmp = dest;
	while(*tmp) tmp++;
	for(; *src1; tmp++, src1++) *tmp = *src1;
	for(; *src2; tmp++, src2++) *tmp = *src2;
	*tmp = *src2;
	return dest;
}

int main(void)
{
	char buf[1024];
	strcpy(buf, "Hello");
	printf(mystrcat(buf, " world", "!\n"));
	return 0;
}

The memory fault is probably because you didn't allocate space for your buffers. If you change char buf[1024] to char *buf, you will get an memory failure because there is no space allocated to copy the strings in.

>> In my functions, I get memory fault error at execution time.

That's because you are returning the address of a local variable. If you declared the char* on the stack (in the function), then you will get that error. So what you should do is what Magos suggested, allocate the memory dynamically and return the pointer. And like Magos said "Just remember to deallocate the allocated memory with delete".

Code:

char* function()
{
     char array[10];

     strcpy( array, "Hello" );

     return array;  // Dragons be here!!!! You cannot do this
}

Magos has already shown you how it should be done.

Hi,

Thanks for your good explanations. But seems that "new" function is a C++ one. I'm using C and I cannot use "new" function. But I'm sure that the problem is lack of memory.

Unfortunately, the program is somewhat complicated, and calls lots of functions. So, I think it is not usefull to attach it.

Thanks again.
FE

Originally posted by Magos
You never mention what the function should do

Code:

char* MyFunction(const char* Arg1, const char* Arg2)
{
   char* String = new char[32];
   if(String != NULL)
   {
      strcpy(String, "Well, what should I return?");
   }
   return String;
}

int main()
{
   char* MyPointer;
   MyPointer = MyFunction("Something", "Something else");
   printf("%s", MyPointer);
   if(MyPointer != NULL) delete[] MyPointer;
}

Just remember to deallocate the allocated memory with delete

Thanks everybody,

It is working now, using malloc function...

FE