https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68206
Bug ID: 68206
Summary: ICE: unimplemented: unexpected AST of kind loop_expr
in potential_constant_expression_1
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: preprocessor
Assignee: unassigned at gcc dot gnu.org
Reporter: chrisb2244 at gmail dot com
Target Milestone: ---
Code below hits ICE.
///////////////////////////////////////////////
#include <array>
#include <iostream>
template<typename T, uint N>
class A
{
using Arr = std::array<T,N>;
public:
constexpr A() = default;
constexpr void displayArr() {
for (uint n=0; n<N; n++) {
std::cout << arr_[n];
}
}
private:
static constexpr Arr makeArr() {
Arr temp{};
for (uint n=0; n<N; n++) {
temp[n] = T(n);
}
return temp;
}
static constexpr Arr arr_ = makeArr();
};
int main() {
A<double, 5> a;
a.displayArr(); // If this isn't called - no problems
return 0;
}
///////////////////////////////////////////////
Error:
loopFail.cpp: In instantiation of 'constexpr const Arr A<double, 5u>::arr_':
loopFail.cpp:13:30: required from 'constexpr void A<T, N>::displayArr() const
[with T = double; unsigned int N = 5u]'
loopFail.cpp:31:18: required from here
loopFail.cpp:26:40: error: 'static constexpr A<T, N>::Arr A<T, N>::makeArr()
[with T = double; unsigned int N = 5u; A<T, N>::Arr = std::array<double, 5ul>]'
called in a constant expression
static constexpr Arr arr_ = makeArr();
^
loopFail.cpp:18:26: note: 'static constexpr A<T, N>::Arr A<T, N>::makeArr()
[with T = double; unsigned int N = 5u; A<T, N>::Arr = std::array<double, 5ul>]'
is not usable as a constexpr function because:
static constexpr Arr makeArr() {
^
loopFail.cpp:18:26: sorry, unimplemented: unexpected AST of kind loop_expr
loopFail.cpp:18:26: internal compiler error: in
potential_constant_expression_1, at cp/constexpr.c:4639
0x8064db potential_constant_expression_1
../../gcc-svn-sources/gcc/cp/constexpr.c:4639
0x805d0d potential_constant_expression_1
../../gcc-svn-sources/gcc/cp/constexpr.c:4257
0x805d0d potential_constant_expression_1
../../gcc-svn-sources/gcc/cp/constexpr.c:4257
0x805d0d potential_constant_expression_1
../../gcc-svn-sources/gcc/cp/constexpr.c:4257
0x7fd453 require_potential_rvalue_constant_expression(tree_node*)
../../gcc-svn-sources/gcc/cp/constexpr.c:4680
0x7fd453 explain_invalid_constexpr_fn(tree_node*)
../../gcc-svn-sources/gcc/cp/constexpr.c:842
0x7fdbc1 cxx_eval_call_expression
../../gcc-svn-sources/gcc/cp/constexpr.c:1258
0x7ffa11 cxx_eval_constant_expression
../../gcc-svn-sources/gcc/cp/constexpr.c:3207
0x805211 cxx_eval_outermost_constant_expr
../../gcc-svn-sources/gcc/cp/constexpr.c:3746
0x686fbe store_init_value(tree_node*, tree_node*, vec<tree_node*, va_gc,
vl_embed>**, int)
../../gcc-svn-sources/gcc/cp/typeck2.c:823
0x5ed78f check_initializer
../../gcc-svn-sources/gcc/cp/decl.c:6111
0x60cdb4 cp_finish_decl(tree_node*, tree_node*, bool, tree_node*, int)
../../gcc-svn-sources/gcc/cp/decl.c:6739
0x642270 instantiate_decl(tree_node*, int, bool)
../../gcc-svn-sources/gcc/cp/pt.c:21459
0x6c0a22 mark_used(tree_node*, int)
../../gcc-svn-sources/gcc/cp/decl2.c:5152
0x64d7bb tsubst_copy
../../gcc-svn-sources/gcc/cp/pt.c:13889
0x659ce2 tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
../../gcc-svn-sources/gcc/cp/pt.c:16692
0x65b6e8 tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
../../gcc-svn-sources/gcc/cp/pt.c:15910
0x65a1b7 tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
../../gcc-svn-sources/gcc/cp/pt.c:15879
0x6462e0 tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
../../gcc-svn-sources/gcc/cp/pt.c:15498
0x644a26 tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
../../gcc-svn-sources/gcc/cp/pt.c:14875
I'm not certain the code is valid, but even in the case it isn't - shouldn't I
just be told what is wrong with it?
In particular, the error line:
makeArr() [ with T = ... ] is not usable as a constexpr function because:
static constexpr Arr makeArr() {
^
doesn't tell me much.
