The following program compiles correctly. I believe it should not because bind should not be in the global namespace. (If you take A out of std this program fails as one would expect.) ------------------------------------- // Compile with: g++ test.cpp -std=c++0x -c #include <functional> namespace std { class A {}; } void f(std::A a) { bind(&f, a); } ------------------------------------- Output of g++ -v: Using built-in specs. Target: x86_64-linux-gnu Configured with: ../src/configure -v --with-pkgversion='Ubuntu 4.4.3-4ubuntu5' --with-bugurl=file:///usr/share/doc/gcc-4.4/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --enable-shared --enable-multiarch --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.4 --program-suffix=-4.4 --enable-nls --enable-clocale=gnu --enable-libstdcxx-debug --enable-plugin --enable-objc-gc --disable-werror --with-arch-32=i486 --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 4.4.3 (Ubuntu 4.4.3-4ubuntu5)
No this is not in the global namespace but rather namelookup looks at std::bind when one of the arguments are in std namespace. namespace std { class A {}; } namespace std { template<typename A> void g(void (*a)(A), A); } void h(std::A a) { g(&h, a); }
right, this is Argument Dependent Lookup and is a feature of C++