Pointer arithmetic not detected by -Wall

[Pavel Roskin]

Hello!

gcc-2.95.2 doesn't detect some very suspicious uses of pointer arithmetic
by default. This progam causes no warnings:

void* func()
{
        void *prt = 0;
        return prt++;
}

even if compiled by:
gcc -c -W -Wall bad.c

I need to specify -Wpointer-arith to get the warning. Most people believe
that -Wall covers all the cases that can and should be avoided as long as
gcc can detect them.

Incrementing void pointers is really bad. HP-UX native CC doesn't even
compile it. I can imagine compilers that add other value than 1, also "for
convenience". This means that the risk of generating bad code is very
high.

I suggest adding -Wpointer-arith to the flags turned on by -Wall.

Regards,
Pavel Roskin