https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69712
Bug ID: 69712 Summary: Storing and reusing a method pointer as compile time value Product: gcc Version: 5.2.1 Status: UNCONFIRMED Keywords: rejects-valid Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: realloc at outlook dot de Target Milestone: --- Created attachment 37617 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=37617&action=edit preprocessed file Storing a method pointer as compile-time value and reusing it as non-type parameter fails. version: g++ (Ubuntu 5.2.1-22ubuntu2) 5.2.1 20151010 os: Ubuntu 15.10 system: Kernel 4.3.0-040300rc6-generic x86_64 GNU/Linux result of compilation attempt: g++ --std=c++14 testcase.cpp -o test ----------------------------------------- testcase.cpp: In function ‘int main()’: testcase.cpp:52:48: error: no matching function for call to ‘callMethod(A&)’ callMethod<decltype(ptr::value), ptr::value>(a); ^ testcase.cpp:33:16: note: candidate: template<class T, typename method_ptr< <template-parameter-1-1> >::type fun, class Class, class ... Args> decltype(auto) callMethod(Class&, Args&& ...) decltype(auto) callMethod(Class & obj, Args && ... args) ^ testcase.cpp:33:16: note: template argument deduction/substitution failed: testcase.cpp:52:48: error: ‘Value<void (A::*)(), &A::sayHi>::value’ is not a valid template argument for type ‘method_ptr<void (A::* const)()>::type {aka void (A::* const)()}’ callMethod<decltype(ptr::value), ptr::value>(a); ^ testcase.cpp:52:48: error: it must be a pointer-to-member of the form ‘&X::Y’ testcase.cpp:52:48: error: could not convert template argument ‘Value<void (A::*)(), &A::sayHi>::value’ to ‘method_ptr<void (A::* const)()>::type {aka void (A::* const)()}’ More detailed: g++ --std=c++14 -v -save-temps testcase.cpp | head --------------------------------------------------- Using built-in specs. COLLECT_GCC=g++ COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/5/lto-wrapper Target: x86_64-linux-gnu Configured with: ../src/configure -v --with-pkgversion='Ubuntu 5.2.1-22ubuntu2' --with-bugurl=file:///usr/share/doc/gcc-5/README.Bugs --enable-languages=c,ada,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-5 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-vtable-verify --enable-libmpx --enable-plugin --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-5-amd64/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-5-amd64 --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-5-amd64 --with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --enable-objc-gc --enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu Thread model: posix gcc version 5.2.1 20151010 (Ubuntu 5.2.1-22ubuntu2) COLLECT_GCC_OPTIONS='-std=c++14' '-v' '-save-temps' '-shared-libgcc' '-mtune=generic' '-march=x86-64' /usr/lib/gcc/x86_64-linux-gnu/5/cc1plus -E -quiet -v -imultiarch x86_64-linux-gnu -D_GNU_SOURCE testcase.cpp -mtune=generic -march=x86-64 -std=c++14 -fpch-preprocess -fstack-protector-strong -Wformat -Wformat-security -o testcase.ii ignoring duplicate directory "/usr/include/x86_64-linux-gnu/c++/5" ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu" ignoring nonexistent directory "/usr/lib/gcc/x86_64-linux-gnu/5/../../../../x86_64-linux-gnu/include" #include "..." search starts here: #include <...> search starts here: /usr/include/c++/5 /usr/include/x86_64-linux-gnu/c++/5 /usr/include/c++/5/backward /usr/lib/gcc/x86_64-linux-gnu/5/include /usr/local/include /usr/lib/gcc/x86_64-linux-gnu/5/include-fixed /usr/include/x86_64-linux-gnu /usr/include End of search list. COLLECT_GCC_OPTIONS='-std=c++14' '-v' '-save-temps' '-shared-libgcc' '-mtune=generic' '-march=x86-64' /usr/lib/gcc/x86_64-linux-gnu/5/cc1plus -fpreprocessed testcase.ii -quiet -dumpbase testcase.cpp -mtune=generic -march=x86-64 -auxbase testcase -std=c++14 -version -fstack-protector-strong -Wformat -Wformat-security -o testcase.s GNU C++14 (Ubuntu 5.2.1-22ubuntu2) version 5.2.1 20151010 (x86_64-linux-gnu) compiled by GNU C version 5.2.1 20151010, GMP version 6.0.0, MPFR version 3.1.3, MPC version 1.0.3 GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072 GNU C++14 (Ubuntu 5.2.1-22ubuntu2) version 5.2.1 20151010 (x86_64-linux-gnu) compiled by GNU C version 5.2.1 20151010, GMP version 6.0.0, MPFR version 3.1.3, MPC version 1.0.3 GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072 Compiler executable checksum: 5ed623d6fe11f4bcc1afee70f77e33b0 testcase.cpp: In function ‘int main()’: testcase.cpp:52:48: error: no matching function for call to ‘callMethod(A&)’ callMethod<decltype(ptr::value), ptr::value>(a); ^ testcase.cpp:33:16: note: candidate: template<class T, typename method_ptr< <template-parameter-1-1> >::type fun, class Class, class ... Args> decltype(auto) callMethod(Class&, Args&& ...) decltype(auto) callMethod(Class & obj, Args && ... args) ^ testcase.cpp:33:16: note: template argument deduction/substitution failed: testcase.cpp:52:48: error: ‘Value<void (A::*)(), &A::sayHi>::value’ is not a valid template argument for type ‘method_ptr<void (A::* const)()>::type {aka void (A::* const)()}’ callMethod<decltype(ptr::value), ptr::value>(a); ^ testcase.cpp:52:48: error: it must be a pointer-to-member of the form ‘&X::Y’ testcase.cpp:52:48: error: could not convert template argument ‘Value<void (A::*)(), &A::sayHi>::value’ to ‘method_ptr<void (A::* const)()>::type {aka void (A::* const)()}’