Hello,

I think you solved the mystery.

You're right, the basic problem is not a const problem, but a * [] problem

As a test.c:
int main (void)
{
int data[3];
*(data++);
return 1;
}

gcc test.c  gives:
-- wrong type argument to increment

But:
int main (void)
{
int *data;
*(data++);
return 1;
}

Compiles just fine with gcc.


I didn't take a look at the latest CVS snapshot, but this might be a good thing to fix it so that the gcc build doesn't break in the future and others spend time asking themselves what's so funny about this */[] things :)


I'll post a patch later if anyone is interested, this kind of problem arises in a few lines.


Denis



Christian Hudon wrote:



The compilers yells at me on line 233 of libFLAC/lpc.c

*(residual++) = *(data++) - (sum >> lp_quantization);
--> data is const and cannot be modified

Funny thing is, if data is declared:
  const FLAC__int32 *data
instead of
  const FLAC__int32 data[]

everything is ok.

Is this a bug in my compiler, or a personnal lack of understanding of
the difference in C between *data and data[] ?


I'm not a great language lawyer, but I don't think you can modify the pointer when something is declared int foo[]. You can modify the data pointed to, with foo[0] = 42, etc. but you can't do stuff like foo++ or foo = (int*)something. The same error would show up with FLAC__int32 * const data. If you want to change the pointer, you need to declare it as a pointer with int *foo (or const int *foo, which means you can modify the pointer, but not the data it points to).


My 2 cents. I'll go back to lurking now. :-)

Christian



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