Functions const argument

Question

I wander why c++ allows to declare this?

void f(int x);

int main()
{
     int x;
     const int y=0;
     f(x);
     f(y);
}

void f(const int x)
{
}

Why compiler allows you declare function with one signature, but define with another (cv qualifier added)?

It started off from C allowing to declare functions with no signatures at all. — user7860670, Jun 07 '18 at 08:08
Almost dupe, just wrong way around: [Why does a function declaration with a const argument allow calling of a function with a non-const argument?](//stackoverflow.com/q/3681188) — Baum mit Augen, Jun 07 '18 at 08:09
Parameter cv qualifier is not a part of function signature. Also see this question: ["Functions with const arguments and Overloading"](https://stackoverflow.com/questions/3682049/functions-with-const-arguments-and-overloading) — AMA, Jun 07 '18 at 08:15
@EduardRistimyan Sorry got confused by you saying both had different signatures — Killzone Kid, Jun 07 '18 at 08:18
I think the reasoning here might be that whether or not something like an `int` parameter is declared `const` does not impact the _caller_ of the function in any way. It just means that it can't be changed within the function body. Something like that, anyway. — Paul Sanders, Jun 07 '18 at 08:39
the parameter being declared as const is an implementation detail and actually not part of the function interface — 463035818_is_not_a_number, Jun 07 '18 at 08:52
@user463035818 Yes, I guess we're saying the same thing. For an `int` parameter (as opposed to a pointer or a reference). — Paul Sanders, Jun 07 '18 at 08:55
@PaulSanders uh yes I knew i missed some details, however, also for a pointer it doenst matter for the caller if the pointer itself is declared as const, or does it? — 463035818_is_not_a_number, Jun 07 '18 at 08:57
@user463035818 [Sure does](http://www.cplusplus.com/reference/cstring/strchr/). — Paul Sanders, Jun 07 '18 at 08:59
@PaulSanders [for the pointer itself it think it doesnt matter](https://ideone.com/yV2lO0) — 463035818_is_not_a_number, Jun 07 '18 at 09:01
@user463035818 I don't understand that, sorry. The point I was trying to make is that, in a function signature, there's a difference between declaring a parameter `char *` and `const char *`, as the link shows. — Paul Sanders, Jun 07 '18 at 09:01
@PaulSanders i completely agree on that, but afaik its irrelevant whether the parameter is `int * const` or `int *` — 463035818_is_not_a_number, Jun 07 '18 at 09:02
@user463035818 Oh, I see. If you put the `const` _there_, then yes. — Paul Sanders, Jun 07 '18 at 09:03
Portability warning: This fails to compile under some compilers (e.g. Solaris C++ compiler). It is indeed kind of compiler bug, however if you need to deploy to Solaris and need to live with that compiler, you are out of luck and have to avoid this. — EmDroid, Jun 07 '18 at 09:18

Functions const argument

0 Answers0