Questions about const.

Questions about const.

[Ryan Lortie]

[please excuse if this is re-post.  i don't think the first message made
it]

GCC generates some warnings when doing type conversions in places that I
don't believe the warnings are required.  It'd be be cool if someone
could explain it to me.  I have an example program here:

http://manic.desrt.ca/const.c

I'm guessing that, by the C standard, arrays that contain items of
different types are always considered incompatible and since 'char *'
and 'const char *' are different types then 'const char **' and 'char
**' are incompatible pointers.  This just doesn't seem very useful when
one of the base types is always safe to automatically promote to the
other (in this case, char * -> const char *) and there is no chance that
an unnoticed conversion could ever occur in the other direction without
generating another warning/error.


Any feedback at all is appreciated -- many thanks.


Cheers.

Re: Questions about const.

[Ian Lance Taylor]

Ryan Lortie <desrt@desrt.ca> writes:

> GCC generates some warnings when doing type conversions in places that I
> don't believe the warnings are required.  It'd be be cool if someone
> could explain it to me.  I have an example program here:
> 
> http://manic.desrt.ca/const.c
> 
> I'm guessing that, by the C standard, arrays that contain items of
> different types are always considered incompatible and since 'char *'
> and 'const char *' are different types then 'const char **' and 'char
> **' are incompatible pointers.  This just doesn't seem very useful when
> one of the base types is always safe to automatically promote to the
> other (in this case, char * -> const char *) and there is no chance that
> an unnoticed conversion could ever occur in the other direction without
> generating another warning/error.

As you say, this is from the C standard.  gcc tries to follow the
standard.

Ian