The following code causes an internal compiler error when compiled with g++ without options:
namespace N{template<class T> void foo();} using namespace N; template<class T> void foo(){} template void foo<int>(); Compiler info: Using built-in specs. Target: x86_64-unknown-linux-gnu Configured with: ../gcc-4.0.1/configure --prefix=/usr/local/compilers/gcc-4.0.1-x86_64-x86_64 --enable-languages=c,c++ --enable-bootstrap Thread model: posix gcc version 4.0.1 The code compiles with a useful diagnostic (and no internal error) when compiled with this newer version of gcc: Using built-in specs. Target: x86_64-redhat-linux Configured with: ../configure --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --enable-shared --enable-threads=posix --enable-checking=release --with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions --enable-libgcj-multifile --enable-languages=c,c++,objc,obj-c++,java,fortran,ada --enable-java-awt=gtk --disable-dssi --enable-plugin --with-java-home=/usr/lib/jvm/java-1.4.2-gcj-1.4.2.0/jre --with-cpu=generic --host=x86_64-redhat-linux Thread model: posix gcc version 4.1.2 20070626 (Red Hat 4.1.2-14) -- Summary: Internal compiler error on (invalid) explicit template instantiation of template function Product: gcc Version: 4.1.2 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: cas43 at cs dot stanford dot edu http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39155