[Gcl-devel] Type-punning

[Camm Maguire]

Greetings!  OK, I've fixed the strict-aliasing/type-punning errors
gcc-3.3 reports with default optimization.  To refresh our memories,
strict-aliasing is an optimization which relies on the ability to
separate memory locations for objects of different type.  One quick
and dirty response for GCL would be to add -fno-strict-aliasing to the
flags, but I like to take advantage of all the optimization we can
get!

In any case, I want to make sure I just haven't fooled the warning
code in gcc.  The fixes fall into two categories.  In the o/
directory, I've defined explicit unions containing both the input and
output types, and used union element assignments to do the type
conversion.  I'm pretty confident about this.

In the lsp/ et. al. directories, we cast pointers in the middle of a
function call in two places, for example:

parse_key_rest_new(V203,narg,Vcs +3,(struct key *)&LI26key,first,ap);
static void LnkT35(){ call_or_link(VV[35],(void **)&Lnk35);} /* 
ARRAY-IN-BOUNDS-P */

My solution here was to have the compiler write instead

parse_key_rest_new(V203,narg,Vcs +3,(struct key *)(void *)&LI26key,first,ap);
static void LnkT35(){ call_or_link(VV[35],(void **)(void *)&Lnk35);} /* 
ARRAY-IN-BOUNDS-P */

with which there are no warnings.  Of course this could have been done
in several other ways.  Is this legit?

Take care,

-- 
Camm Maguire                                            address@hidden
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