https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68612
Bug ID: 68612
Summary: Const-compatibility in C
Product: gcc
Version: 5.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: alexreg at gmail dot com
Target Milestone: ---
There is a widely-known deficiency in C involving the passing of arguments to
'more' const-qualified parameters. e.g.
```
void func (int const * const * foo)
{
if (foo)
;
}
int main ()
{
int * * foo = 0;
func (foo);
}
```
fails with
warning: passing argument 1 of 'func' from incompatible pointer type
[-Wincompatible-pointer-types]
note: expected 'const int **' but argument is of type 'int **'
as per the C99 specification. C++ is more liberal in this respect, but no less
safe, since the above will compile without warnings. (Note that if the
parameter type for `func` in the above example is instead `int const * *`,
there exist slightly obscure ways for code to modify `**foo` without warnings
or errors being generated, thus violating const-correctness. This is not the
case as long as the parameter type is `int const * const *`.)
Would it possible to enable a feature on the C compiler and GCC driver for
const-compatibility to work as it does for C++, in the more liberal manner? As
a point of annoyance for many C programmers (in my experience), this would at
least allow those of us who don't care about standards compliance so much to
circumvent this design deficiency.
