https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93901
Bug ID: 93901
Summary: noexcept specifier on ctor does not work with
constexpr variable or expression
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: paul.groke at dynatrace dot com
Target Milestone: ---
Seems like with GCC 10, only the literal `true` works as expected in noexcept
specifiers for ctors. Other expressions that evaluate to "true" result in ctors
that test as "noexcept(false)". Noexcept specifiers on functions seem to work
just fine though.
Example:
#include <type_traits>
#include <new>
extern void *mem;
constexpr bool YES = true;
struct NoexceptTrueCtor {
NoexceptTrueCtor() noexcept(true);
};
void NoexceptTrueFun() noexcept(true);
struct NoexceptYesCtor {
NoexceptYesCtor() noexcept(YES);
};
void NoexceptYesFun() noexcept(YES);
struct NoexceptOneEqOneCtor {
NoexceptOneEqOneCtor() noexcept(1 == 1);
};
void NoexceptOneEqOneFun() noexcept(1 == 1);
struct NoNoexceptCtor {
NoNoexceptCtor();
};
void NoNoexceptFun();
static_assert(std::is_nothrow_default_constructible<NoexceptTrueCtor>::value,
"1"); // OK
static_assert(noexcept(new(mem) NoexceptTrueCtor), "2"); // OK
static_assert(noexcept(NoexceptTrueFun()), "3"); // OK
static_assert(std::is_nothrow_default_constructible<NoexceptYesCtor>::value,
"4"); // fail
static_assert(noexcept(new(mem) NoexceptYesCtor), "5"); // fail
static_assert(noexcept(NoexceptYesFun()), "6"); // OK
static_assert(std::is_nothrow_default_constructible<NoexceptOneEqOneCtor>::value,
"7"); // fail
static_assert(noexcept(new(mem) NoexceptOneEqOneCtor), "8"); // fail
static_assert(noexcept(NoexceptOneEqOneFun()), "9"); // OK
static_assert(!std::is_nothrow_default_constructible<NoNoexceptCtor>::value,
"10"); // OK
static_assert(!noexcept(new(mem) NoNoexceptCtor), "11"); // OK
static_assert(!noexcept(NoNoexceptFun()), "12"); // OK
This fails with
<source>:32:71: error: static assertion failed: 4
32 |
static_assert(std::is_nothrow_default_constructible<NoexceptYesCtor>::value,
"4"); // fail
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~
<source>:33:15: error: static assertion failed: 5
33 | static_assert(noexcept(new(mem) NoexceptYesCtor), "5"); // fail
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<source>:36:76: error: static assertion failed: 7
36 |
static_assert(std::is_nothrow_default_constructible<NoexceptOneEqOneCtor>::value,
"7"); // fail
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~
<source>:37:15: error: static assertion failed: 8
37 | static_assert(noexcept(new(mem) NoexceptOneEqOneCtor), "8"); // fail
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Compiler returned: 1
Tested with godbolt.org: https://godbolt.org/z/BvXe4K
x86-64, g++ (Compiler-Explorer-Build) 10.0.1 20200223 (experimental)
GCC versions 9.2 and older compile the above code just fine as do Clang, MSVC
and ICC.
