As with the C front end, G++ understands the C99 feature of restricted pointers, specified with the __restrict__
, or __restrict
type qualifier. Because you cannot compile C++ by specifying the -std=c99
language flag, restrict
is not a keyword in C++.
In addition to allowing restricted pointers, you can specify restricted references, which indicate that the reference is not aliased in the local context.
void fn (int *__restrict__ rptr, int &__restrict__ rref)
{
/* ... */
}
In the body of fn
, rptr points to an unaliased integer and rref refers to a (different) unaliased integer.
You may also specify whether a member function's this pointer is unaliased by using __restrict__
as a member function qualifier.
void T::fn () __restrict__
{
/* ... */
}
Within the body of T::fn
, this has the effective definition T *__restrict__ const this
. Notice that the interpretation of a __restrict__
member function qualifier is different to that of const
or volatile
qualifier, in that it is applied to the pointer rather than the object. This is consistent with other compilers that implement restricted pointers.
As with all outermost parameter qualifiers, __restrict__
is ignored in function definition matching. This means you only need to specify __restrict__
in a function definition, rather than in a function prototype as well.
© Free Software Foundation
Licensed under the GNU Free Documentation License, Version 1.3.
https://gcc.gnu.org/onlinedocs/gcc-6.3.0/gcc/Restricted-Pointers.html