https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66649
Bug ID: 66649
Summary: variable template specializations not being found
Product: gcc
Version: 5.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: public at alisdairm dot net
Target Milestone: ---
Created attachment 35841
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35841&action=edit
C++ code that should compile in C++14 mode, but fails
The attached file shows a simple test case for variable templates that I
believe is correct, and passes with Clang:
template <typename T, typename U>
constexpr bool is_same_v = false;
template <typename T>
constexpr bool is_same_v<T, T> = true;
template <typename T>
auto make() -> T;
template <typename T>
void AssertMakeSame() {
static_assert( is_same_v<T, T>, "Type should be the same as itself");
static_assert( is_same_v<decltype(make<T>()), T>, "make should produce the
same type");
};
int main() {
AssertMakeSame<int>();
// AssertMakeSame<int const>(); // Should be an error
AssertMakeSame<int *>();
}
In gcc 5, I get an error that the partial specialization must be at namespace
scope, but this appears to be fixed in trunk. However, all 4 static asserts
fire in both trunk and 5.
Tested with:
g++ -v
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/opt/local/libexec/gcc/x86_64-apple-darwin14/6.0.0/lto-wrapper
Target: x86_64-apple-darwin14
Configured with:
/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_lang_gcc6/gcc6/work/gcc-6-20150614/configure
--prefix=/opt/local --build=x86_64-apple-darwin14
--enable-languages=c,c++,objc,obj-c++,lto,fortran,java
--libdir=/opt/local/lib/gcc6 --includedir=/opt/local/include/gcc6
--infodir=/opt/local/share/info --mandir=/opt/local/share/man
--datarootdir=/opt/local/share/gcc-6 --with-local-prefix=/opt/local
--with-system-zlib --disable-nls --program-suffix=-mp-6
--with-gxx-include-dir=/opt/local/include/gcc6/c++/ --with-gmp=/opt/local
--with-mpfr=/opt/local --with-mpc=/opt/local --with-isl=/opt/local
--enable-stage1-checking --disable-multilib --enable-lto
--enable-libstdcxx-time --with-as=/opt/local/bin/as --with-ld=/opt/local/bin/ld
--with-ar=/opt/local/bin/ar --with-bugurl=https://trac.macports.org/newticket
--with-pkgversion='MacPorts gcc6 6-20150614_0'
Thread model: posix
gcc version 6.0.0 20150614 (experimental) (MacPorts gcc6 6-20150614_0)
and with:
g++ -v
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/opt/local/libexec/gcc/x86_64-apple-darwin14/5.1.0/lto-wrapper
Target: x86_64-apple-darwin14
Configured with:
/opt/local/var/macports/build/_opt_mports_dports_lang_gcc5/gcc5/work/gcc-5.1.0/configure
--prefix=/opt/local --build=x86_64-apple-darwin14
--enable-languages=c,c++,objc,obj-c++,lto,fortran,java
--libdir=/opt/local/lib/gcc5 --includedir=/opt/local/include/gcc5
--infodir=/opt/local/share/info --mandir=/opt/local/share/man
--datarootdir=/opt/local/share/gcc-5 --with-local-prefix=/opt/local
--with-system-zlib --disable-nls --program-suffix=-mp-5
--with-gxx-include-dir=/opt/local/include/gcc5/c++/ --with-gmp=/opt/local
--with-mpfr=/opt/local --with-mpc=/opt/local --with-isl=/opt/local
--enable-stage1-checking --disable-multilib --enable-lto
--enable-libstdcxx-time --with-as=/opt/local/bin/as --with-ld=/opt/local/bin/ld
--with-ar=/opt/local/bin/ar --with-bugurl=https://trac.macports.org/newticket
--with-pkgversion='MacPorts gcc5 5.1.0_1'
Thread model: posix
gcc version 5.1.0 (MacPorts gcc5 5.1.0_1)
