https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69700
Bug ID: 69700
Summary: [C++14] constexpr incorrectly implies const
Product: gcc
Version: 5.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: michael.price at synopsys dot com
Target Milestone: ---
Created attachment 37602
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=37602&action=edit
preprocessed source
The following code (derived from the subject of CWG DR 1683) should be
ill-formed in C++14:
struct A {
constexpr A() {}
constexpr operator int() { return 1; }
};
template <int> struct X {};
constexpr A a;
X<a> x;
GCC compiles it as if it were C++11, under which it is well-formed. The output
below is from 5.2.0, but the behavior 4.9.0 through 5.3.0 seemed consistent.
$ g++ -v -save-temps -c -std=c++14 constexpr-vs-const.cpp
Using built-in specs.
COLLECT_GCC=/opt/pkg/gcc-5.2.0/bin/g++
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-5.2.0/configure --prefix=/opt/pkg/gcc-5.2.0
--program-suffix=-5.2.0 --enable-languages=c,c++
Thread model: posix
gcc version 5.2.0 (GCC)
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-c' '-std=c++14' '-shared-libgcc'
'-mtune=generic' '-march=x86-64'
/opt/pkg/gcc-5.2.0/libexec/gcc/x86_64-unknown-linux-gnu/5.2.0/cc1plus -E
-quiet -v -imultiarch x86_64-linux-gnu -D_GNU_SOURCE constexpr-vs-const.cpp
-mtune=generic -march=x86-64 -std=c++14 -fpch-preprocess -o
constexpr-vs-const.ii
ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"
ignoring nonexistent directory
"/opt/pkg/gcc-5.2.0/lib/gcc/x86_64-unknown-linux-gnu/5.2.0/../../../../x86_64-unknown-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
/opt/pkg/gcc-5.2.0/lib/gcc/x86_64-unknown-linux-gnu/5.2.0/../../../../include/c++/5.2.0
/opt/pkg/gcc-5.2.0/lib/gcc/x86_64-unknown-linux-gnu/5.2.0/../../../../include/c++/5.2.0/x86_64-unknown-linux-gnu
/opt/pkg/gcc-5.2.0/lib/gcc/x86_64-unknown-linux-gnu/5.2.0/../../../../include/c++/5.2.0/backward
/opt/pkg/gcc-5.2.0/lib/gcc/x86_64-unknown-linux-gnu/5.2.0/include
/usr/local/include
/opt/pkg/gcc-5.2.0/include
/opt/pkg/gcc-5.2.0/lib/gcc/x86_64-unknown-linux-gnu/5.2.0/include-fixed
/usr/include/x86_64-linux-gnu
/usr/include
End of search list.
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-c' '-std=c++14' '-shared-libgcc'
'-mtune=generic' '-march=x86-64'
/opt/pkg/gcc-5.2.0/libexec/gcc/x86_64-unknown-linux-gnu/5.2.0/cc1plus
-fpreprocessed constexpr-vs-const.ii -quiet -dumpbase constexpr-vs-const.cpp
-mtune=generic -march=x86-64 -auxbase constexpr-vs-const -std=c++14 -version -o
constexpr-vs-const.s
GNU C++14 (GCC) version 5.2.0 (x86_64-unknown-linux-gnu)
compiled by GNU C version 5.2.0, GMP version 4.3.2, MPFR version
2.4.2, MPC version 0.8.1
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
GNU C++14 (GCC) version 5.2.0 (x86_64-unknown-linux-gnu)
compiled by GNU C version 5.2.0, GMP version 4.3.2, MPFR version
2.4.2, MPC version 0.8.1
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: d48b14d3a677b3306bfa594605d7fb25
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-c' '-std=c++14' '-shared-libgcc'
'-mtune=generic' '-march=x86-64'
as -v --64 -o constexpr-vs-const.o constexpr-vs-const.s
GNU assembler version 2.22 (x86_64-linux-gnu) using BFD version (GNU Binutils
for Ubuntu) 2.22
COMPILER_PATH=/opt/pkg/gcc-5.2.0/libexec/gcc/x86_64-unknown-linux-gnu/5.2.0/:/opt/pkg/gcc-5.2.0/libexec/gcc/x86_64-unknown-linux-gnu/5.2.0/:/opt/pkg/gcc-5.2.0/libexec/gcc/x86_64-unknown-linux-gnu/:/opt/pkg/gcc-5.2.0/lib/gcc/x86_64-unknown-linux-gnu/5.2.0/:/opt/pkg/gcc-5.2.0/lib/gcc/x86_64-unknown-linux-gnu/
LIBRARY_PATH=/opt/pkg/gcc-5.2.0/lib/gcc/x86_64-unknown-linux-gnu/5.2.0/:/opt/pkg/gcc-5.2.0/lib/gcc/x86_64-unknown-linux-gnu/5.2.0/../../../../lib64/:/lib/x86_64-linux-gnu/:/lib/../lib64/:/usr/lib/x86_64-linux-gnu/:/opt/pkg/gcc-5.2.0/lib/gcc/x86_64-unknown-linux-gnu/5.2.0/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-c' '-std=c++14' '-shared-libgcc'
'-mtune=generic' '-march=x86-64'
$
