https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80061
Bug ID: 80061
Summary: error on constexpr function with an unevaluated throw
Product: gcc
Version: 7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
Target Milestone: ---
The following valid test case was reduced from the invalid one submitted with
bug 70377. GCC rejects the constexpr function simple_find because it contains
a throw statement even though the statement is not evaluated in the (constexpr)
contexts the function is called. Clang 5.0 and EDG eccp 4.13 both accept the
program.
$ cat t.C && gcc -Wall -Wextra -Wpedantic t.C
struct array
{
int a [3];
constexpr const int& operator[](int i) const { return a[i]; }
};
constexpr int
simple_find (const array &a, int x)
{
for (int i = 0; i != 3; ++i)
if (a[i] == x)
return i;
throw;
}
static constexpr array some_ints { { 10, 11 } };
static_assert (simple_find (some_ints, 10) == 0, "#1");
static_assert (simple_find (some_ints, 11) == 1, "#2");
t.C: In function ‘constexpr int simple_find(const array&, int)’:
t.C:14:3: error: expression ‘<throw-expression>’ is not a constant expression
throw;
^~~~~
t.C: At global scope:
t.C:19:1: error: non-constant condition for static assertion
static_assert (simple_find (some_ints, 10) == 0, "#1");
^~~~~~~~~~~~~
t.C:19:28: error: ‘constexpr int simple_find(const array&, int)’ called in a
constant expression
static_assert (simple_find (some_ints, 10) == 0, "#1");
~~~~~~~~~~~~^~~~~~~~~~~~~~~
t.C:20:1: error: non-constant condition for static assertion
static_assert (simple_find (some_ints, 11) == 1, "#2");
^~~~~~~~~~~~~
t.C:20:28: error: ‘constexpr int simple_find(const array&, int)’ called in a
constant expression
static_assert (simple_find (some_ints, 11) == 1, "#2");
~~~~~~~~~~~~^~~~~~~~~~~~~~~
