error: "BOOST_CLANG" is not defined

[Ivo Raisr <ivosh@…>]

boost/detail/container_fwd.hpp:72:9: error: "BOOST_CLANG" is not defined

This header file at line 72 contains the following:

#if BOOST_CLANG

But BOOST_CLANG is not even defined in my environment (gcc 4.1.2 on RHEL 5.x). I've checked all other occurrences of BOOST_CLANG in boost header files and all contain construct such as

defined(BOOST_CLANG)

The problem is present in boost 1.48.0 as well. I changed line 72 to:

#if defined(BOOST_CLANG) && (BOOST_CLANG)

and it seems to work now.

Perhaps it could be changed just to:

#if defined(BOOST_CLANG)

Should you need more information, just ping me.

Ivo Raisr

[Daniel James]

(In [75544]) Detail: Revert [67484] in container_fwd. Refs #6139

[Daniel James]

Sorry I'd meant to revert that change before, but forgot to.

[Jürgen Hunold]

Revision ​https://svn.boost.org/trac/boost/changeset/75544 just broke my clang builds. The correct solution would be to either

• use #if defined(BOOST_CLANG) see container_fwd_guarded.diff
• change "class" to struct see containner_fwd_simple.diff

The interesting thing is that container_fwd.hpp contains a msvc-suppression for struct/class mismatch: line 104ff:

#if defined(BOOST_MSVC)
#pragma warning(push)
#pragma warning(disable:4099) // struct/class mismatch in fwd declarations
#endif

So the "correct" solution depends on how the corresponding standard library declares struct or class "complex". At least the guarded approach prevents clang from emitting a warning.

[anonymous]

Detecting clang is not the right thing to do, it should be based on the standard library not the compiler. How did it break your build?

[Jürgen Hunold]

clang issues a "-Wmismatched-tags" warning for struct/class mismatches. This is C4099 in msvc as mentioned before.

To be compatible with the msvc-settings, we have -Werror=mismatched-tags to reduce the noise in our sources.

The proper way seems to be do "struct complex;" for all and be happy.

If all standard libraries do it that way, of course.

[Daniel James]

I tried to fix this in [75561], although I'm not sure if it will work as I don't have clang on windows. If it doesn't, can you build and run config_info (from libs/config/test/config_info.cpp) and attach the output.

I might just change it to always disable forwarding for clang, clang parses the standard headers pretty quickly so it shouldn't make any real difference.

[Jürgen Hunold]

Does not work. You should #define BOOST_CONTAINER_FWD_COMPLEX_STRUCT for #if defined(BOOST_CLANG). And this is on Linux, my settings are just for reducing cross-plattform compiler/stdlib inconsistencies. I think I'll #define BOOST_DETAIL_NO_CONTAINER_FWD in the meantime.

[anonymous]

Sorry, I'm not going to do anything until I have a better idea of what your setup is. If you attach the output of config_info.cpp that would help. Or if that's too difficult, you could just tell me.

It'd also help if you explained why you think that the definition of complex is determined by the compiler and not the standard library. I'm not making a change just because it happens to work on one particular setup without understanding the reason behind wanting that change.

On my linux box clang uses gcc's standard library by default, and in that complex is defined as class complex. There must be some reason why it isn't on yours, but without more information I can only guess. At the moment, I don't know which standard library you're using or which version of clang you're using.

[Jürgen Hunold]

Output of config_info_threadedfor clang 3.1

[Jürgen Hunold]

clang error backtrace

[Jürgen Hunold]

Yes, makes sense. I've attached the output of config_info (threaded) and my full clang backtrace of the error. If you need more information or more tests, please ping me again.

[Daniel James]

(In [75600]) Detail: Fix BOOST_CONTAINER_FWD_COMPLEX_STRUCT. Refs #6139.

My last change was wrong, it isn't struct for Dinkumware. In GCC's standard library it's declared as a class, but later defined as a struct. This is so far untested as I'm building the latest trunk version of clang (the warning doesn't show for the current clang release).

[Daniel James]

(In [75909]) Unordered: Fix complex type for gcc's standard library. Fixes #6139.

I haven't had any confirmation, but I assume this fixes the problem.

[anonymous]

Oops, the subject of that changeset should have started with 'Detail' not 'Unordered'.