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Re: rationale for eliding modifications to string constants
Andrew Pinski <pinskia@gmail.com> writes:
> On Tue, Sep 14, 2010 at 11:47 AM, Uday P. Khedker <uday@cse.iitb.ac.in> wrote:
>> Attached please find two dumps t.c.032t.mergephi1 and t.c.033t.cddce1.
>> The assignment is present in the former while it disappears in the
>> latter. The latter dump is the output of the dead code elimination
>> pass pass_cd_dce. So this is indeed an instance of dead code elimination.
>>
>> But may be you are right, what facilitate dead code elimination
>> be based on modification of read-only data. However, if that is
>> the case, I wonder what is the reason why change happens when s is
>> an array...
>
> What is being done is correct really. Since the string has the type
> of const char[]. Since you have an explicit cast to get rid of the
> const qualifer, we don't warn. I don't see a bug here at all really.
> You are invoking an undefined behavior, GCC keep the assignment around
> or get rid of it.
I agree that this is technically correct but I still think it is a bad
choice. Fortunately it does seem to work as I want in mainline.
Ian