Re: Thoughts on "const tree" and "const rtx"?

[Theodore Papadopoulo <Theodore dot Papadopoulo at sophia dot inria dot fr>]

You know gcc better than me, but let's try a guess.
const has not been used because gcc has been converted to C90 only 
very recently. And IIRC, const was introduced with C90.
IMHO adding const is good, if not for anaything else, at least for
documentation purposes.

I have played a little with the idea of adding a switch (eg 
warn-possible-constant-parm) that allow the compiler to warn when
some parameter could be made const (yes I know, the warning cannot
be made totally 100% safe at least for C++). I have 
a partial patch for C++, but I'm somewhat stuck at the moment.

The basic idea would be to remember the constness of a variable (or 
method) but do nothing at first and considering it as const (for C++, 
do it in such a way not to alter mangling!).

- If an error message related to constness is trigerred 
  then look at the declaration and only emit the warning/error if the
  relevant variable (method) is declared const. Otherwise, mark the 
  parameter as being non constant.

- If the switch is given and if the function have been compiled without
  error, emit a warning for all the parameters for which const is not specified
  and that have not triggered any error. 

I'm playing with this basically as an exercise to learn some 
internals of gcc, but with the idea of using this as an helper 
to constify codes (like gcc!).

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Theodore Papadopoulo
Email: Theodore.Papadopoulo@sophia.inria.fr Tel: (33) 04 92 38 76 01
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