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Date: Mon, 09 Sep 2002 18:45:00 -0000
From: Andrew Cagney <ac131313@ges.redhat.com>
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To: David Carlton <carlton@math.stanford.edu>
Cc: gdb <gdb@sources.redhat.com>
Subject: Re: naive GDB programming style questions
References: <ro1u1kyah7d.fsf@jackfruit.Stanford.EDU>
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> 1) It seems to me that some parts of GDB's source use NULL while other
>    parts use 0.  Is one or the other of these generally preferred?
> 
> 2) Am I correct in observing that GDB frowns on code like the
>    following:
> 
>      char *p = calculate_p ();
> 
>      if (!p)
>        p_is_zero ();

I'll assume that you ment ``p_is_null()''.

>    preferring this instead?
> 
>      char *p = calculate_p ();
> 
>      if (p == NULL)
>        p_is_zero ();
> 
>    Does it matter that p in a pointer rather than an integer, or that
>    the code is testing for zeroness rather than nonzeroness?

If you've a copy of the ISO C and C++ manuals, have a look at what they 
have to say about ``NULL'' pointers.  It's weird.

Anyway, for GDB, ``p == NULL'' is recommended to make it clear that the 
pointer is being tested and not the underlying value.

> 3) Is it possible to get CC Mode to indent in the way that GDB seems
>    to prefer?  I'm having a hard time getting structs to be indented
>    as follows:
> 
>      struct foo
>        {
>          int mem;
>        };

Just use:

struct foo
{
   int mem;
};

which is what is output by gdb_indent.sh and emacs.  The strange 
indentation that you've encountered dates back to an earlier version of 
indent.

Must get around to sending the FSF coding standards group a patch that 
documents this (it was agreed to in principle some time ago).

>    without screwing up my preferred indentation when doing non-GDB
>    programming, namely
> 
>      struct foo {
>        int mem;
>      };
> 
>    Of course, I can write functions to toggle between the two; but
>    given that both styles seem to be able to coexist for enums, maybe
>    it's possible to get them to coexist for enums.  (I'm certainly no
>    CC Mode expert...)

Andrew