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From: "Uecker, Martin" <Martin.Uecker@med.uni-goettingen.de>
To: "torvalds@linux-foundation.org" <torvalds@linux-foundation.org>
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Subject: detecting integer constant expressions in macros
Thread-Topic: detecting integer constant expressions in macros
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Date: Tue, 20 Mar 2018 22:13:35 +0000
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Hi Linus,

here is an idea:

a test for integer constant expressions which returns an
integer constant expression itself which should be suitable
for passing to __builtin_choose_expr might be:

#define ICE_P(x) (sizeof(int) == sizeof(*(1 ? ((void*)((x) * 0l)) :
(int*)1)))

This also does not evaluate x itself on gcc although this is
not guaranteed by the standard. (And I haven't tried any older
gcc.)

Best,
Martin