https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80739
Bug ID: 80739
Summary: Accessing value of X through a Y glvalue in a constant
expression
Product: gcc
Version: 6.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: vince.rev at gmail dot com
Target Milestone: ---
Created attachment 41352
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=41352&action=edit
Example of the bug
Consider the following valid code in C++14 (compiles without problem under
clang):
// ==========================================================================
//
#include <iostream>
template <class T> struct element {
constexpr element() noexcept: x0(0), x1(0), x2(0), x3(0) {}
T x0; int x1, x2, x3;
};
template <class T> struct container {
constexpr container() noexcept: data() {data = element<T>();}
element<T> data;
};
template <class T> constexpr bool test() {
return (container<T>(), true);
}
int main() {
constexpr bool tmp0 = test<int>(); // works
constexpr bool tmp1 = test<std::size_t>(); // fails
return tmp0 && tmp1;
}
// ==========================================================================
//
Compilation fails under g++-5 (g++-5 (Ubuntu 5.4.1-2ubuntu1~16.04) 5.4.1
20160904) with the following message:
## --------------------------------------------------------------------------
##
gcc_compiler_error.cpp: In function ‘int main()’:
gcc_compiler_error.cpp:16:44: in constexpr expansion of ‘test<long unsigned
int>()’
gcc_compiler_error.cpp:16:45: in constexpr expansion of ‘container<long
unsigned int>()’
gcc_compiler_error.cpp:16:45: internal compiler error: unexpected expression
‘*(container<long unsigned int>*)this’ of kind mem_ref
constexpr bool tmp1 = test<std::size_t>(); // fails
^
Please submit a full bug report,
with preprocessed source if appropriate.
See <file:///usr/share/doc/gcc-5/README.Bugs> for instructions.
## --------------------------------------------------------------------------
##
Compilation fails under g++-6 (g++-6 (Ubuntu 6.2.0-3ubuntu11~16.04) 6.2.0
20160901) with the following message:
## --------------------------------------------------------------------------
##
gcc_compiler_error.cpp: In function ‘int main()’:
gcc_compiler_error.cpp:16:44: in constexpr expansion of ‘test<long unsigned
int>()’
gcc_compiler_error.cpp:16:45: in constexpr expansion of ‘container<long
unsigned int>()’
gcc_compiler_error.cpp:16:45: error: accessing value of ‘<anonymous>’ through a
‘char [20]’ glvalue in a constant expression
constexpr bool tmp1 = test<std::size_t>(); // fails
^
## --------------------------------------------------------------------------
##
Other versions may be affected (not tested).
