[cfe-dev] Compile to ast and llvm bytecode using Clang API

[João Paulo Labegalini de Carvalho via cfe-dev]

>
> I just got back around to trying the example program. I had to make a few
> changes to get the code to compile.
>
You are right, after I have sent you the code I realized it was not
correct. The CommandLine you pass to Driver::BuildCompilation must be a
ArrayRef not a string. Sorry for the confusion.


> When I try the program it says it is unable to find clang++ which is
> definitely on my system. Do I need to hard code the path to clang++?
>
Yes, the path for clang/llvm tools must be absolute paths. Thats why I find
it easier to re-use the command line from the compilation database. In
order to generate the compile_commands.json (a.k.a. compilation database),
you just need to pass -DCMAKE_EXPORT_COMPILE_COMMANDS to cmake while
configuring the build of your project. After that, you can retrieve the
compile command for a specific file using the
tooling::CompilationDatabase::getCompileCommmands()
<https://clang.llvm.org/doxygen/classclang_1_1tooling_1_1CompilationDatabase.html>
method.



> On 11/11/18 2:33 PM, João Paulo Labegalini de Carvalho wrote:
>
> Michael,
>
> The easiest way to use Clang API to perform "standard" compiler tasks is
> through the Driver class
> <https://clang.llvm.org/doxygen/classclang_1_1driver_1_1Driver.html>.
> Basically what you need to do is setup a command line invocation, using
> the flags from a compilation database or adding your own, build a
> Compilation object and execute it through the driver.
>
> For instance:
>
> std::string CommandLine = "clang++ -Wall -O3 -emit-llvm -o test.bc
> test.cpp";
> clang::DiagnosticOptions* DiagOptions = new DiagnosticOptions();
> clang::DiagnosticConsumer *DiagClient = new
> TextDiagnosticPrinter(llvm::errs(), DiagOptions);
> llvm::IntrusiveRefCntPtr<clang::DiagnosticIDs> DiagID(new
> clang::DiagnosticIDs());
> clang::DiagnosticsEngine Diags(DiagID, DiagOptions, DiagClient);
> clang::driver::Driver TheDriver("clang++",
> llvm::sys::getDefaultTargetTriple(), Diags);
> const std::unique_ptr<driver::Compilation>
> compilation(TheDriver.BuildCompilation(CommandLine));
> if (!compilation) { llvm::errs() << "failed to build compilation
> object!\n"; }
> llvm::SmallVector<std::pair<int, const driver::Command*>,10>
> failingCommands;
> int res = TheDriver.ExecuteCompilation(*compilation, failingCommands);
> if (res < 0) {
>   ProcessingFailed = true;
>   for (const std::pair<int, const driver::Command*>& p : failingCommands) {
>     if (p.first) {
>       TheDriver.generateCompilationDiagnostics(*compilation, *p.second);
>     }
>   }
> }
>
>
> On Sun, Nov 11, 2018 at 6:53 PM Michael Collison via cfe-dev <
> cfe-dev at lists.llvm.org> wrote:
>
>> I have a requirement to parse a .cpp file to a .ast file and a .bc file.
>> I have the parsing, with filtering of the AST working using the the
>> tooling tempalte on this page:
>> https://clang.llvm.org/docs/RAVFrontendAction.html. I also need to
>> generate LLVM code to write out to a .bc file. I tried using :
>>
>> tool.run (newFrontEndActionFactory<EmitBCAction>().get())
>>
>> where tool is an instance of ClangTool but received an error saying "not
>> enough position command line arguments specified". Any ideas? Are there
>> any examples I can look at?
>>
>> Regards,
>>
>> Michael Collison
>>
>>
>> _______________________________________________
>> cfe-dev mailing list
>> cfe-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>
>
>
> --
> João Paulo L. de Carvalho
> Computer Science |  IC-UNICAMP | Campinas , SP - Brazil
> jaopaulolc at gmail.com
> joao.carvalho at ic.unicamp.br
> j160924 at dac.unicamp.br
>
>

-- 
João Paulo L. de Carvalho
Computer Science |  IC-UNICAMP | Campinas , SP - Brazil
jaopaulolc at gmail.com
joao.carvalho at ic.unicamp.br
j160924 at dac.unicamp.br
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