pass a pointer-to-pointer, or return a pointer? Post: 302273896

Sponsored Content

Top Forums Programming pass a pointer-to-pointer, or return a pointer? Post 302273896 by spirtle on Tuesday 6th of January 2009 05:43:33 AM

01-06-2009

Registered User

I prefer the second form because:

The interface is simpler: one parameter in, the answer returned. You just check whether the pointer is null to verify success. The first form has some kind of other return value to check, which could be boolean, but I cannot tell, so I would have to look up the definitions of OK and NOK. And it is unclear from the interface whether I also need to check the pointer value, or indeed whether the pointer is NULL on failure. Looking into you implementation I can see that OK is returned if and only if the pointer is valid and the pointer is NULL on failure, but then I can write
Code:
```
char *my_pmem;
my_malloc(64, &my_pmem);
if(my_pmem){
  ...
}
```
so the return value is redundant -- it gives me no extra information.
However, if you want the function to indicate more than just a simple fail/succeed (e.g. different failure modes) then the first way is the only way to do it.
It mimics the standard malloc(3) function -- or it would do if the parameter was of type size_t rather than int -- and therefore has the benefit of familiarity, and makes it easier to port code written with malloc to use my_malloc.

spirtle

View Public Profile for spirtle

Find all posts by spirtle

10 More Discussions You Might Find Interesting

1. Programming

pointer

void main() { int a={1,2,3,4,5,6,7,8,9,10}; int *p=a; int *q=&a; cout<<q-p+1<<endl; } The output is 10, how? if we give cout<<q it will print the address, value won't print.... if we give cout<<p it will print the address, value won't print.... p has the base addr; q...

2. Programming

Regarding char Pointer

Hi, char *s="yamaha"; cout<<s<<endl; int *p; int i=10; p=&i; cout<<p<<endl; 1) For the 1st "cout" we will get "yamaha" as output. That is we are getting "content of the address" for cout<<s. 2) But for integer "cout<<p" we are getting the "address only". Please clarify how we are...

3. Programming

pointer problem

could any one tell why the following is showing segmentation fault while using **ptr but working fine using **a #include<stdio.h> ...

4. Programming

far pointer

what is far pointer in C

5. Programming

How to return void function pointer

Hello all im trying to build function that will return void function pointer what is mean is ( not working ) the main function void * myClass::getFunction(int type){ if(type==1) return &myClass::Test1; if(type==2) return &myClass::Test2; } void myClass::Test1(){...

6. Programming

matrix pointer

Can anyone tell me what the following statements do? float (*tab); tab=(float (*)) calloc(MAXCLASS, (MAXCLASS+1)*sizeof(float));

7. Programming

Pointer Arithmetic In C

I have a fundamental question on C pointer arithmetry.. Suppose i have a c string pointer already pointing to a valid location, Can I just do a charptr = charptr +1; to get to the next location, irregardless if my program is 32 or 64 bits? or should i do it this way: charptr =...

8. Programming

Pointer to pointers

Hi guys, I'm trying to understand pointers in C and made a simple example and I've problems with It. Can someone help? #include <stdio.h> #include <stdlib.h> #include <assert.h> int f1(char **str_); int main(int argc, char **argv) { char *str = NULL; f1(&str); ...

9. Programming

Pointer for 2D array seems to be 3D in C

I am struggling with the pointer to 2D-array (cf: 2D array of pointers). Can anybody help me elaborate how the pointer x moves in the memory to access the individual of y, especially the high lighted lines? I have talked to one of the curators of the forum, but I am still not quite clear. Here...

10. Programming

Segmentation fault when I pass a char pointer to a function in C.

I am passing a char* to the function "reverse" and when I execute it with gdb I get: Program received signal SIGSEGV, Segmentation fault. 0x000000000040083b in reverse (s=0x400b2b "hello") at pointersExample.c:72 72 *q = *p; Attached is the source code. I do not understand why...

LEARN ABOUT HPUX

memalign

memalign(3C)															      memalign(3C)

NAME

       memalign() - allocate aligned memory

SYNOPSIS

DESCRIPTION

       allocates  space  for a block of size bytes, whose address is a multiple of boundary.  The space is not initialized. The boundary must be a
       power of 2.

EXTERNAL INFLUENCES

       employs the allocator.  For tuning information, see the malloc(3C) man page.

RETURN VALUE

       Upon successful completion, returns a pointer to space aligned to a multiple of boundary.  Otherwise, it returns a NULL pointer.

DIAGNOSTICS

       returns a NULL pointer if there is no available memory, or if the value of boundary is not a power of 2.

ERRORS

	      sets     to and returns a NULL pointer when an out-of-memory condition arises.

	      sets     to and returns a NULL pointer when the value of boundary is not a power of 2.

	      sets     to and returns a NULL pointer when the memory being managed by has been detectably corrupted.

WARNINGS

       For warnings, see the malloc(3C) man page.

SEE ALSO

       thread_safety(5).

STANDARDS CONFORMANCE

       There appear to be no standards applicable to Some implementations do not check that boundary is a power of 2.  The HP-UX implementation is
       not derived from any predecessor.

																      memalign(3C)