[cfe-dev] Extracting the include tree from a source file

[Bertjan Broeksema]

Paul Davey wrote:

> On Fri, Nov 19, 2010 at 8:21 AM, Bertjan Broeksema
> <broeksema at kde.org> wrote:
>> Nico Weber wrote:
>>
>>> Hm, this _might_ be because clang comes with a few standard headers,
>>> see clang/lib/Headers. Maybe clang adds these to the search path
>>> somehow. Adding a gentoo-specific include path is the correct fix in
>>> this case.
>>
>> Yes it is because clang needs this standard headers installed in
>> /usr/lib/clang/2.8/include (on linux of course, don't know about other
>> platforms). From libs/Driver/Driver.cpp: (line 76 and further in 2.8)
>>
>> // Compute the path to the resource directory.
>> llvm::sys::Path P(Dir);
>> P.eraseComponent(); // Remove /bin from foo/bin
>> P.appendComponent("lib");
>> P.appendComponent("clang");
>> P.appendComponent(CLANG_VERSION_STRING);
>> ResourceDir = P.str();
>>
>>
>> I don't really understand why. Moreover, I don't understand why
>> AddGnuCPlusPlusIncludePaths in InitHeaderSearch.cpp is implemented as is.
>> For example take:
>>
>> AddGnuCPlusPlusIncludePaths(
>> "/usr/lib/gcc/x86_64-pc-linux-gnu/4.4.4/include/g++-v4",
>> "x86_64-pc-linux-gnu", "32", "", triple);
>>
>> The directory above (i.e.
>> /usr/lib/gcc/x86_64-pc-linux-gnu/4.4.3/include/) also contains the
>> headers which are in /usr/lib/clang/2.8/include. So I wondered why
>> AddGnuCPlusPlusIncludePaths, doesn't add this path too so that the clang
>> include directory is not required.
>>
>> This might be Gentoo specific, meaning that for other distros the current
>> code *does* find the standard headers and therefore doesn't need the
>> clang include path. If so, please tell me. In that case for the Gentoo
>> adding a line like:
>>
>> AddPath( "/usr/lib/gcc/x86_64-pc-linux-gnu/4.4.4/include/"
>> , System, true, false, false );
>>
>> would remove the need for custom apps to add the clang include dir.
>>
>> Cheers,
>>
>> Bertjan
>>
> The headers in lib/clang/2.8/include are clang header, the ones for
> gcc are gcc header, the ones for clang should be used with clang.
> That function only adds the C++ header path which is actually for
> libstdc++ not part of gcc the other headers are part of gcc and
> shouldn't be messed with AFAIK.

> As you said the driver computes the
> path to clangs headers relative to itself, perhaps this should be
> separated into a separate function.

Yes that would be more convenient, or as a define in the config.h file. 
Anything not relying on the clang executable and not requiring any path 
calculations by the client would be okay I guess.

Cheers,

Bertjan