Critical behavioral change between g++-4.4/g++-4.5 and g++-4.6 ?

[Marc Glisse]

Wrong mailing list, you are looking for gcc-help.

On Sun, 21 Aug 2011, Emmanuel Fleury wrote:

> I was trying to compile a project called kyua with g++-4.6 and I did hit a 
> linking error. It seems that a method was missing.
>
> After some discussions with the main developer of the project, it appeared 
> that depending on the version of g++ we were using the build was going nicely 
> (g++-4.4/g++-4.5) or was hitting a linking error (g++-4.6).
>
> Here is the error:
>
> cli/cmd_about_test.cpp:106: error: undefined reference to 
> 'utils::cmdline::base_command<engine::user_files::config>::main(utils::cmdline::ui*, 
> std::vector<std::basic_string<char, std::char_traits<char>, 
> std::allocator<char> >, std::allocator<std::basic_string<char, 
> std::char_traits<char>, std::allocator<char> > > > const&, 
> engine::user_files::config const&)'
> cli/cmd_about_test.cpp:106: error: undefined reference to 
> 'utils::cmdline::base_command<engine::user_files::config>::main(utils::cmdline::ui*, 
> std::vector<std::basic_string<char, std::char_traits<char>, 
> std::allocator<char> >, std::allocator<std::basic_string<char, 
> std::char_traits<char>, std::allocator<char> > > > const&, 
> engine::user_files::config const&)'
> cli/cmd_about_test.cpp:87: error: undefined reference to 
> 'utils::cmdline::base_command<engine::user_files::config>::main(utils::cmdline::ui*, 
> std::vector<std::basic_string<char, std::char_traits<char>, 
> std::allocator<char> >, std::allocator<std::basic_string<char, 
> std::char_traits<char>, std::allocator<char> > > > const&, 
> engine::user_files::config const&)'
> cli/cmd_about_test.cpp:87: error: undefined reference to 
> 'utils::cmdline::base_command<engine::user_files::config>::main(utils::cmdline::ui*, 
> std::vector<std::basic_string<char, std::char_traits<char>, 
> std::allocator<char> >, std::allocator<std::basic_string<char, 
> std::char_traits<char>, std::allocator<char> > > > const&, 
> engine::user_files::config const&)'
> collect2: ld returned 1 exit status
>
> And, indeed, when getting the symbols from the static libraries built with 
> g++-4.4 (I had it on my system, but I can install g++-4.5 if needed) and 
> g++-4.6, I got the following output (you will see that the method requested 
> by the linker is missing in libcli.a):
[...]
> So, now, I am looking for help to know if the problem is coming from the code 
> or from g++-4.6.

>From the code. The definition (not just declaration) of templates should 
be available everywhere they are used (or you can manually force 
instantiation in one translation unit and inhibit it in the others).

> (sorry I didn't manage to circumvent the problem to a small piece of 
> code),

Er, what did you try?

-- 
Marc Glisse