const function parameters

[Tox|k]

I have a few questions about const function paramaters ie.

void constfunc(const int *i) {}
//as opposed to
void func(int *i) {}

Is there any benefit to using them, either than maybe keeping things well formed and informative? Is the code that's generated for the function any different than not using const parameters, or is this just a compile time check?

I just have doubts about them seeing as all one has to do to modify the variable is declare another pointer, copy over the address of the const, and then use the new pointer to modify the data (not that I'd ever do such a thing ).

Actually, is there much point to using const at all, either than having some useful compiler warnings when you try to do something you shouldn't?

[laserlight]

Const correctness happens to be more of a C++ concept than a C concept at this point of time, but you could still read this FAQ section: Const correctness.

C compilers are more lax about code that attempts to circumvent const.

[matsp]

A good compiler will most likely optimize external functions that use const better than non-const functions - in the sense that if you have something in a register, that is also pointed to by a parameter to a function, it can't continue to hold the value in a register.

Of course, if the function is in the same file (or in a header that is included by the source file), and it's inlined, then compiler should be able to figure out that the value is not being changed anyways.

--
Mats

[Sander]

C compilers are more lax about code that attempts to circumvent const.

Unfortunately, it is "implementation-defined" what happens when you modify a const pointer anyway. You may get a compiler warning, but it will compile.

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Computer Programming: An Introduction for the Scientifically Inclined

[Elysia]

That's why C is so incredibly unsafe.
It's far better to write C++/C (compiling C inside C++). No worries about modifying const then.