const int *p vs. int const *p - Is const after the type acceptable?

Question

My co-worker is 0 for 2 on questions he has inspired (1, 2), so I thought I\'d give him a chance to catch up.

Our latest disagreement is over the style issue of wher

Answer 1

I like to to use the following form for declaring "manifest constants". In this case, the value itself is a constant so I put the "const" first (same as Bjarne) to emphasize that the constness should be manifest at compile-time, and usable as such for specific optimizations by the compiler.

const int i = 123;

For declaring references which will not be used to modify the value, I use the following form which emphasizes the fact that the identifier is a "constant reference". The referenced value may or may not be a constant. [Related discussion: Would you even be using "const" for function parameters if they were not pointers or references? Use of 'const' for function parameters]

void fn( int const & i );

For pointers, I use the same form that I use for references, for essentially the same reason (although the term "constant pointer" seems a little more ambiguous than "constant reference").

void fn( int const * i );

Also, as another poster noted, this form remains consistent when you have multiple levels of indirection.

void fn( int const * const * i );

The final scenario, where you are declaring a pointer which is constant is pretty rare in my experience with C++. In any case, you don't really have any choices here. [This case demonstrates that the most consistent approach would be to put the word "const" after the type -- since that is, in fact, required for this particular declaration.]

void fn( int * const i );

...unless you use a typedef.

typedef int * IntPtr;

void fn1( const IntPtr i );
void fn2( IntPtr const i );

One final note: Unless you are working in a low-level domain, most C++ code should never declare a pointer. Therefore, that aspect of this discussion is probably more relevant to C.