[Bug-gnulib] GNUlib realloc POSIX comformance

[Yoann Vandoorselaere]

Hi,

I'm in the process of using GNUlib realloc(), but have some question
relating to it's code:

The GNUlib realloc implementation will:

1) use malloc if the provided pointer is NULL.
2) set size to 1 if provided len is zero.

#1 is perfectly okay with me since some implementation of realloc() will
crash if the provided pointer is NULL, not comforming to the POSIX
standard.

#2, however doesn't sound okay:

- Quoting POSIX malloc definition:
   "If the size of the space requested is 0, the behavior is 
    implementation-defined: the value returned shall be either a null  
    pointer or a unique pointer."

- Quoting POSIX realloc definition:
  1. "If size is 0 and ptr is not a null pointer, the object pointed to 
      is freed."

  2. "If size is 0, either a null pointer or a unique pointer that can  
      be successfully passed  to  free() shall be returned." Which mean
      this is implementation defined.

First, the way GNUlib realloc() is implemented contradict with POSIX
definition #1. 

GNUlib realloc() will set size to 1 if the provided size is 0,
regardless of whether the provided pointer is NULL, which mean we will
allocate a 1 byte block instead of freeing the block when the pointer is
NULL as per #1 POSIX recommendation.

Second, and IMHO GNUlib should not make a choise regarding the
'implementation defined' part of the #2 POSIX definition (setting size
to 1 if the provided size is zero). I personnally would assume a call to
malloc/realloc with size being 0 to be a bug in my code.


So my proposed realloc implementation would look like:

void *realloc(void *ptr, size_t size)
{
        if ( ! ptr )
                return malloc(size);

        if ( size == 0 ) {
                free(ptr);
                return NULL;
        }
        
        return realloc(ptr, size);
}

Note that I'm handling the case where ptr is set and size is not zero
directly because I am not confident that every realloc implementation
comform to this POSIX definition.

Regards,


Ps: also, would it be possible to move the GNUlib realloc license from
GPL to LGPL ?

-- 
Yoann Vandoorselaere <address@hidden>