Re: [AD] constness in ugetx()

[Laurence Withers <lwithers@xxxxxxxxxx>]

Having trawled through the comp.lang.c FAQ, I found:

  http://www.eskimo.com/~scs/C-faq/q11.10.html

Why can't I pass a char ** to a function which expects a const char **? 
----------------------------------------------------------------------

You can use a pointer-to-T (for any type T) where a pointer-to-const-T
is expected. However, the rule (an explicit exception) which permits
slight mismatches in qualified pointer types is not applied recursively,
but only at the top level.

You must use explicit casts (e.g. (const char **) in this case) when
assigning (or passing) pointers which have qualifier mismatches at other
than the first level of indirection.

Hrm... great. So it seems that there are only two `good' solutions to
this problem:

 - remove `const'-correctness from Allegro, which would break all 
   programs using `const'-correctness.
 - provide two versions of the function (problem in C; not in C++).
   Logically, `ugetx' would take `char**' (since it was like this before
   `const'-correctness came along), and `ugetx_const' would take
   `const char**'.

Bye for now,
-- 
Laurence Withers, lwithers@xxxxxxxxxx
                http://www.lwithers.demon.co.uk/

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