[RFC] GCC 8 Project proposal: Extensions supporting C Metaprogramming, pseudo-templates

Vincent Lefevre vincent+gcc@vinc17.org
Mon May 15 11:31:00 GMT 2017


On 2017-05-12 15:59:44 -0500, Daniel Santos wrote:
> [...] But from a conceptual standpoint, I believe the term
> "constant-expression" would be incorrect because the C standard
> defines this constraint: (6.6.3 of C11) "Constant expressions shall
> not contain assignment, increment, decrement, function-call, or
> comma operators, except when they are contained within a
> subexpression that is not evaluated." I definitely do need to study
> the C specs more carefully to make sure I fully understand how this
> is used and how it's changed over different revisions of the spec.

GCC already regards some function calls are acceptable in
constant expressions, when builtins are used, e.g. fabs (2.0),
contrary to Clang. The builtin is even used when <math.h> is
not included (note that Clang has the same behavior here). So,
there may be several issues. I've reported:

  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80756

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Vincent Lefèvre <vincent@vinc17.net> - Web: <https://www.vinc17.net/>
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