Messages in this thread | | | From | David Howells <> | Subject | Re: [PATCH] asm-generic: fix -Wtype-limits compiler warnings | Date | Wed, 24 Jul 2019 08:49:31 +0100 |
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Qian Cai <cai@lca.pw> wrote:
> Fix it by moving almost all of this multi-line macro into a proper > function __get_order(), and leave get_order() as a single-line macro in > order to avoid compilation errors.
The idea was that you could compile-time initialise a global variable with get_order():
int a = get_order(SOME_MACRO);
This is the same reason that ilog2() is a macro:
int a = ilog2(SOME_MACRO);
See the banner comment on get_order():
* This function may be used to initialise variables with compile time * evaluations of constants.
If you're moving the constant branch into __get_order(), an inline function, then we'll no longer be able to do this and you need to modify the comment too. In fact, would there still be a point in having the get_order() macro?
Also, IIRC, older versions of gcc see __builtin_constant_p(n) == 0 inside an function, inline or otherwise, even if the passed-in argument *is* constant.
David
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