http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51047
Bug #: 51047 Summary: [C++0x] SFINAE does not handle errors of ambiguous base members Classification: Unclassified Product: gcc Version: 4.7.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ AssignedTo: unassig...@gcc.gnu.org ReportedBy: ai.az...@gmail.com I expect that the following code is compiled successfully. However, the second static_assert results in a hard error without SFINAE. ========== cryolite@blueplanet:~/work/test$ LANG=C ~/local/4.7.0/bin/g++-tlimit -v -save-temps -std=c++0x 5_2_5_5.cpp Using built-in specs. COLLECT_GCC=/home/cryolite/local/4.7.0/bin/g++ COLLECT_LTO_WRAPPER=/home/cryolite/local/4.7.0/libexec/gcc/x86_64-unknown-linux-gnu/4.7.0/lto-wrapper Target: x86_64-unknown-linux-gnu Configured with: /home/cryolite/work/intro/gcc-4.7-20111105/configure --build=x86_64-unknown-linux-gnu --host=x86_64-unknown-linux-gnu --target=x86_64-unknown-linux-gnu --prefix=/home/cryolite/local/4.7.0 --enable-static --enable-shared --enable-multilib --enable-threads=posix --enable-tls --with-arch-32=i686 --with-tune=generic --enable-bootstrap --enable-languages=c,c++ --enable-libssp --enable-libgomp --enable-targets=all --enable-nls --enable-lto --enable-libstdcxx-debug --disable-libstdcxx-pch Thread model: posix gcc version 4.7.0 20111105 (experimental) (GCC) COLLECT_GCC_OPTIONS='-v' '-save-temps' '-std=c++11' '-shared-libgcc' '-mtune=generic' '-march=x86-64' /home/cryolite/local/4.7.0/libexec/gcc/x86_64-unknown-linux-gnu/4.7.0/cc1plus -E -quiet -v -D_GNU_SOURCE 5_2_5_5.cpp -mtune=generic -march=x86-64 -std=c++11 -fpch-preprocess -o 5_2_5_5.ii ignoring nonexistent directory "/home/cryolite/local/4.7.0/lib/gcc/x86_64-unknown-linux-gnu/4.7.0/../../../../x86_64-unknown-linux-gnu/include" #include "..." search starts here: #include <...> search starts here: /home/cryolite/local/4.7.0/lib/gcc/x86_64-unknown-linux-gnu/4.7.0/../../../../include/c++/4.7.0 /home/cryolite/local/4.7.0/lib/gcc/x86_64-unknown-linux-gnu/4.7.0/../../../../include/c++/4.7.0/x86_64-unknown-linux-gnu /home/cryolite/local/4.7.0/lib/gcc/x86_64-unknown-linux-gnu/4.7.0/../../../../include/c++/4.7.0/backward /home/cryolite/local/4.7.0/lib/gcc/x86_64-unknown-linux-gnu/4.7.0/include /usr/local/include /home/cryolite/local/4.7.0/include /home/cryolite/local/4.7.0/lib/gcc/x86_64-unknown-linux-gnu/4.7.0/include-fixed /usr/include End of search list. COLLECT_GCC_OPTIONS='-v' '-save-temps' '-std=c++11' '-shared-libgcc' '-mtune=generic' '-march=x86-64' /home/cryolite/local/4.7.0/libexec/gcc/x86_64-unknown-linux-gnu/4.7.0/cc1plus -fpreprocessed 5_2_5_5.ii -quiet -dumpbase 5_2_5_5.cpp -mtune=generic -march=x86-64 -auxbase 5_2_5_5 -std=c++11 -version -o 5_2_5_5.s GNU C++ (GCC) version 4.7.0 20111105 (experimental) (x86_64-unknown-linux-gnu) compiled by GNU C version 4.7.0 20111105 (experimental), GMP version 5.0.2, MPFR version 3.0.0-p3, MPC version 0.9 GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096 GNU C++ (GCC) version 4.7.0 20111105 (experimental) (x86_64-unknown-linux-gnu) compiled by GNU C version 4.7.0 20111105 (experimental), GMP version 5.0.2, MPFR version 3.0.0-p3, MPC version 0.9 GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096 Compiler executable checksum: 1c96d36acbd98a4b9c0fb64069912a60 5_2_5_5.cpp: In substitution of 'template<class T> decltype (declval<T>().x) f(T*) [with T = D]': 5_2_5_5.cpp:13:27: required from here 5_2_5_5.cpp:2:44: error: request for member 'x' is ambiguous 5_2_5_5.cpp:5:16: error: candidates are: int B2::x 5_2_5_5.cpp:4:16: error: int B1::x cryolite@blueplanet:~/work/test$ cat 5_2_5_5.ii # 1 "5_2_5_5.cpp" # 1 "<command-line>" # 1 "5_2_5_5.cpp" template<typename T> T &&declval(); template<class T> decltype(declval<T>().x) f(T *); template<class T> char f(T); struct B1{ int x; }; struct B2{ int x; }; struct D : public B1, B2{}; struct S { int x; }; int main() { S *p = nullptr; static_assert(sizeof(f(p)) == sizeof(int), ""); D *q = nullptr; static_assert(sizeof(f(q)) == 1u, ""); } ========== Just for reference, the following code is compiled without any error as I expected. ========== template<class T> decltype(T::x) f(T *); template<class T> char f(T); struct B1{ int x; }; struct B2{ int x; }; struct D : public B1, B2{}; struct S { int x; }; int main() { S *p = nullptr; static_assert(sizeof(f(p)) == sizeof(int), ""); D *q = nullptr; static_assert(sizeof(f(q)) == 1u, ""); } ==========