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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/55425] constexpr does not work in many situations (both built-in and user supplied literals) Date: Wed, 21 Nov 2012 12:13:00 -0000 [thread overview] Message-ID: <bug-55425-4-oeZQOPPNEf@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-55425-4@http.gcc.gnu.org/bugzilla/> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55425 --- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-11-21 12:12:19 UTC --- (In reply to comment #0) > > A return statement is not a return statement if the returned value is __func__ > (also true for non-standard identifiers like __PRETTY_FUNCTION__). > > // good > //static const char func[] = "function-name"; > //constexpr const char* x() { return func; } > > // bad > constexpr const char* x() { return __func__;} > > int main() { __builtin_puts(x()); return 0; } The standard says __func__ is a function-local variable, defined as if by constexpr const char* x() { static const char __func__[] = "function-name "; return __func__; } Clearly this is not a valid constexpr function. Changing this would be an extension. > Situation 2: user literals > -------------------------- > > The (obviously constant) string that the compiler builds from the literal is > not constant according to the compiler: > > #include <stdio.h> > > constexpr int valid_bin_number(const char* c) { return *c ? ((*c == '1' || *c > == '0') ? valid_bin_number(c+1) : false ) : true; } > > unsigned int operator"" _bin(const char* str) > { > static_assert(valid_bin_number(str), "not a binary number"); 'str' is not a constant expression, so 'valid_bin_number(str)' is not a constant expression either. This is not a bug. > Situation 3: __m128i type > -------------------------- > > Assigning a literal value to a constexpr __m128 fails because the literal is > not a literal. No, the error says __m128 is not a literal type, which I assume is true. Changing that would be an enhancement request.
next prev parent reply other threads:[~2012-11-21 12:13 UTC|newest] Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-11-21 11:31 [Bug c++/55425] New: constexpr does not work in many situations (both built-in and user supplied) M8R-ug85cr at mailinator dot com 2012-11-21 12:13 ` redi at gcc dot gnu.org [this message] 2012-11-21 12:19 ` [Bug c++/55425] constexpr does not work in many situations (both built-in and user supplied literals) redi at gcc dot gnu.org 2012-11-21 12:41 ` jakub at gcc dot gnu.org 2012-11-21 13:51 ` jakub at gcc dot gnu.org 2012-11-21 20:52 ` glisse at gcc dot gnu.org 2013-07-01 6:14 ` richard-gccbugzilla at metafoo dot co.uk 2014-11-19 10:27 ` paolo.carlini at oracle dot com 2014-11-19 10:37 ` paolo.carlini at oracle dot com 2014-11-19 17:41 ` paolo at gcc dot gnu.org 2014-11-19 17:43 ` paolo.carlini at oracle dot com
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