Re: XMALLOC() et al

[Bruno Haible]

Paul Eggert wrote:
> > GNU gettext uses the XMALLOC macro in more than 100 places. It's
> > just so convenient to do a memory allocation in 1 line of code:
> 
> I find it more convenient to write this:
> 
>    context = xmalloc (sizeof *context);
> 
> than this (taken from GNU gettext):
> 
>    context = XMALLOC (markup_parse_context_ty);

This is where our opionions differ. The first style has three drawbacks:

  * In order to understand what the statement really does, the reader
    has to look up the definition of 'context', to see its type.

  * Typically, right after allocating an object, comes the initialization
    of its members. To make it easy for the reader to verify that this
    initialization is complete, he needs to look up the definition of the
    type quickly. Again, this is harder if the type is not stated explicitly.

  * When there is a copy-and-paste mistake, the first style does not warn,
    but the second style does. For example, suppose we have types
    fun_context, var_context, tag_context and associated local variables, then

      fcontext = xmalloc (sizeof *fcontext);
      vcontext = xmalloc (sizeof *vcontext);
      tcontext = xmalloc (sizeof *vcontext);

    will not warn, whereas

      fcontext = XMALLOC (fun_context);
      vcontext = XMALLOC (var_context);
      tcontext = XMALLOC (var_context);

    will warn.

Which is why I encourage the use of XMALLOC.

Bruno