https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86607
Bug ID: 86607
Summary: constexpr function does not treat function pointers
with external linkage as constexpr
Product: gcc
Version: 8.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: tadeus.prastowo at unitn dot it
Target Milestone: ---
Using http://godbolt.org, I see that the following program compiles in
any clang version that supports `-std=c++14' switch (>= 3.5) but fails
in any GCC version >= 5.1 while compiles in any GCC version <= 4.9.4
that supports `-std=c++14' switch (>= 4.8.5):
template<typename T, T v>
struct carrier {
static constexpr T value = v;
};
template<typename T>
inline constexpr bool nontype_nontemplate_args_eq(T arg1, T arg2) {
return arg1 == arg2;
}
template<typename T1, typename T2>
inline constexpr bool nontype_nontemplate_args_eq(T1, T2) {
return false;
}
int fn1() {
return 2;
}
int fn2() {
return 17;
}
int main() {
return carrier<bool, nontype_nontemplate_args_eq(&fn1, &fn2)>::value;
}
Any GCC version >= 5.1 should compile the program because `&fn1' and `&fn2' as
the arguments of constexpr function `nontype_nontemplate_args_eq' are constexpr
according to the C++ standard http://eel.is/c++draft/expr.const#6.2.
