https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103732
Bug ID: 103732
Summary: Incorrect constexpr evaluation of runtime expression
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: gonzalo.gadeschi at gmail dot com
Target Milestone: ---
GCC 11.2 accepts the following example:
struct S { static constexpr int C = 5; };
void f() {
S s0{}, s1{};
S* a[] = {&s0, &s1};
for (int i = 0; i < 2; ++i) {
constexpr int x = S::C;
constexpr int y = s0.C;
constexpr int z = a[i]->C;
}
}
According to http://eel.is/c++draft/class.static#general-1, the object
expression of s0.C and a[i]->C are evaluated, but for example, a[i] is not a
constant expression.
I think GCC is incorrectly accepting this code.
Clang produces the following error:
<source>:10:23: error: constexpr variable 'z' must be initialized by a constant
expression
constexpr int z = a[i]->C;
^ ~~~~~~~
<source>:10:29: note: read of non-const variable 'i' is not allowed in a
constant expression
constexpr int z = a[i]->C;
^
<source>:7:14: note: declared here
for (int i = 0; i < 2; ++i) {
^
