[cfe-dev] libclang and plugins

[Manuel Klimek]

On Fri Oct 03 2014 at 6:15:34 PM Stefan Kemnitz <kemnitz.stefan at gmail.com>
wrote:

> Mr. Klimek asked me to send my patch to this mailing list.
> Please follow the conversation i had with him.
>

Patches for review should usually have a [PATCH] in the subject and contain
a patch. You can use http://llvm.org/docs/Phabricator.html if you like it,
or you can send a patch file to the mailing list with a short description
of the contents. See http://llvm.org/docs/DeveloperPolicy.html

Cheers,
/Manuel


> Thank you ;)
>
> ---------- Forwarded message ----------
> From: Manuel Klimek <klimek at google.com>
> Date: 2014-10-02 13:33 GMT+02:00
> Subject: Re: [cfe-dev] libclang and plugins
> To: Stefan Kemnitz <kemnitz.stefan at gmail.com>
> Cc: cfe-dev at cs.uiuc.edu
>
>
> Send the patch to cfe-commits and we can loop in all the right people to
> review it / chime in there, I think.
> Generally it sounds like what you did makes sense, but I'm not sure what
> the trade-offs are in various areas here...
>
> On Thu Oct 02 2014 at 12:54:16 PM Stefan Kemnitz <kemnitz.stefan at gmail.com>
> wrote:
>
>> ok i did something that makes it work, but i don't know whether its a
>> good way to do it.
>> It works when the plugin is called from clang and libclang.
>> I even see my errors appear in vim through YouCompleteMe.
>>
>> First i added a method loadPlugins() in CompilerInstance that simply does
>> what it was doing before in ExecuteCompilerInvocation.
>> In ExecuteCompilerIncovation i removed the loading and called the new
>> method.
>> I did the same thing in ASTUnit::Parse.
>> The problem is, that libclang does not export all the needed symbols that
>> are needed for plugins to link against it when loaded.
>> So i added the symbols to tools/libclang/libclang.exports.
>> Additionally i added a dependency to the plugin so that it links against
>> libclang.
>> I think this is not the way it should be done.
>> What would be a better way to do this ?
>>
>> https://gist.github.com/realincubus/6cba9934b0d49f539446
>>
>> Greetings Stefan Kemnitz
>>
>>
>> 2014-09-29 10:57 GMT+02:00 Manuel Klimek <klimek at google.com>:
>>
>>> On Fri Sep 26 2014 at 8:39:37 PM M.Sc. Stefan Kemnitz <
>>> kemnitz.stefan at gmail.com> wrote:
>>>
>>>> Hi,
>>>>
>>>> i am working on a plugin for clang that will show me some custom
>>>> diagnostics.
>>>>
>>>> I extended the "Hello World"-plugin PrintFunctionNames so that it emits
>>>> an errors if it finds a function declaration ( its just a toy plugin )
>>>> Everything works fine if i execute it from command line with clang.
>>>>
>>>>
>>>> -------------------------------------------------------------------------------------
>>>> $ clang -Xclang -load -Xclang <pluginpath>/PrintFunctionNames.so
>>>> -Xclang -add-plugin -Xclang print-fns main.cpp
>>>> top-level-decl: "foo"
>>>> /home/incubus/test/clang-plugins/main.cpp:3:1: error: use of undeclared
>>>> identifier 'foo'
>>>> void foo()
>>>> ^
>>>> /home/incubus/test/clang-plugins/main.cpp:12:5: error: use of
>>>> undeclared identifier 'bar'
>>>>     bar();
>>>>     ^
>>>> top-level-decl: "main"
>>>> /home/incubus/test/clang-plugins/main.cpp:8:1: error: use of undeclared
>>>> identifier 'main'
>>>> int main(int argc, char** argv){
>>>> ^
>>>> 3 errors generated.
>>>>
>>>> ---------------------------------------------------------------------------------------
>>>>
>>>> the first and third error are from my plugin and the second is from
>>>> clang itself.
>>>>
>>>> Now i want to do the same thing through libclang.
>>>> I am using the vim plugin YouCompleteMe to send all of the flags that
>>>> were passed to clang, to libclang.
>>>>
>>>> I followed the path of execution to
>>>> clang_parseTranslationUnit -> clang_parseTranslationUnit2 ->
>>>> clang_parseTranslationUnit_impl ->
>>>>  ASTUnit::LoadFromCommandLine -> ASTUnit::LoadFromCompilerInvocation ->
>>>> ASTUnit::Parse
>>>>
>>>> were the parsing process is started.
>>>>
>>>> in FrontendAction::BeginSourceFile  the method
>>>> FrontendAction::CreateWrappedASTConsumer is called which creates
>>>> ASTConsumers from the plugins.
>>>> I found out that the Consumer is not created because the
>>>> FrontendPluginRegistry does not contain any plugins.
>>>> This is due to the fact that the plugin was never loaded.
>>>>
>>>> I searched the codebase for the loading routines and found out that the
>>>> only loading is in clang::ExecuteCompilerInvocation.
>>>> I know that clang_parseTranslationUnit is supposed to Parse the
>>>> translation unit not to execute the whole compiler.
>>>>
>>>> My question is:
>>>>
>>>> Is there any way to load the plugin earlier so that it can be executed
>>>> while parsing?
>>>> Or if it is not possible. Is there some other way to add custom error
>>>> messages that will be emitted when running clang_parseTranslationUnit?
>>>>
>>>
>>> I think the right solution is to add a way to load plugins when running
>>> with libclang.
>>> I see 2 options:
>>> 1. add a call to libclang to allow loading of plugins
>>> + less complexity in the driver
>>> - libclang tools need to get explicit support for this
>>> 2. make the driver allow loading clang plugins
>>> + "just works" with any editor integration
>>> - more complexity in the driver
>>>
>>> I'm leaning towards (2). If you want to give implementing it a try, I'd
>>> be happy to review patches...
>>>
>>> Cheers,
>>> /Manuel
>>>
>>>
>>>>
>>>>
>>>> Greetings Stefan Kemnitz
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> cfe-dev mailing list
>>>> cfe-dev at cs.uiuc.edu
>>>> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
>>>>
>>>
>>
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