[cfe-dev] using the original file name for compiling preprocessed files ("-main-file-name"?)

[Robert Lytton]

Hi Richard,

The data route to set the ModuleID is below.
At some stage the code should have used  getCompilerInstance().getCodeGenOpts().MainFileName I believe.
However, I am not familiar enough to know who needs the real file name and who needs the original file name.

I tried a patch at  FrontendAction::BeginSourceFile(), but not all unit tests passed - not looked into why yet.
A patch later when we create the BackendConsumer()  "seems to work" - see below-below.

Robert


lib/Frontend/CompilerInstance.cpp
    CompilerInstance::ExecuteAction()
        (Input = getFrontendOpts())

lib/Frontend/FrontendAction.cpp
        BeginSourceFile(Input)
            InFile = Input.getFile();
            FrontendAction::CreateWrappedASTConsumer(InFile)

lib/CodeGen/CodeGenAction.cpp
                CodeGenAction::CreateASTConsumer(InFile)
                    OS(Infile)
                    BackendConsumer(infile) : ASTConsumer

 lib/CodeGen/ModuleBuilder.cpp
                         clang::CreateLLVMCodeGen(ModuleName)
                            CodeGeneratorImpl(ModuleName)
llvm
                                llvm::Module(ModuleName)




diff --git a/lib/CodeGen/CodeGenAction.cpp b/lib/CodeGen/CodeGenAction.cpp
index 795b127..d952fbf 100644
--- a/lib/CodeGen/CodeGenAction.cpp
+++ b/lib/CodeGen/CodeGenAction.cpp
@@ -543,10 +543,12 @@ ASTConsumer *CodeGenAction::CreateASTConsumer(CompilerInstance &CI,
     LinkModuleToUse = ModuleOrErr.get();
   }

+  StringRef mainFileName = getCompilerInstance().getCodeGenOpts().MainFileName;
+  if (mainFileName.empty())
+    mainFileName = InFile;
   BEConsumer = new BackendConsumer(BA, CI.getDiagnostics(), CI.getCodeGenOpts(),
                                    CI.getTargetOpts(), CI.getLangOpts(),
-                                   CI.getFrontendOpts().ShowTimers, InFile,
+                                   CI.getFrontendOpts().ShowTimers, mainFileName,
                                    LinkModuleToUse, OS.release(), *VMContext);
   return BEConsumer;
 }


________________________________
From: metafoo at gmail.com [metafoo at gmail.com] on behalf of Richard Smith [richard at metafoo.co.uk]
Sent: 02 May 2014 00:35
To: Robert Lytton
Cc: cfe-dev at cs.uiuc.edu
Subject: Re: [cfe-dev] using the original file name for compiling preprocessed files ("-main-file-name"?)

On Thu, May 1, 2014 at 2:22 AM, Robert Lytton <robert at xmos.com<mailto:robert at xmos.com>> wrote:
Hi,

I would like to call clang twice, once to preprocess and second time to compile.
The second time clang is called, I would like to pass in the original file name for it to use as the ModuleID.
I tried to use:
   clang -E test.c -o tmp.i
   clang -S -x c tmp.i -o test.s    -Xclang -main-file-name -Xclang test.c   -emit-llvm

However, the ModuleID is 'tmp.i' rather than that passed in by '-main-file-name'.

This seems like a bug to me; -main-file-name should be used as the name of the input in all respects other than where we find it on disk. Care to put together a patch to fix this? (I doubt you'll be able to get anyone else to care much about what ends up in ModuleID, so I think you'll need to do the work yourself here...)

Same with:
    clang -cc1 -triple x86_64-unknown-linux-gnu -x c tmp.i -o test.s  -main-file-name test.c -emit-llvm


I am trying to achieve the same affect as using "-fpreprocessed -dumpbase <file>" with llvm-gcc.
Here it seems the gcc front end fetches the file name from the first line of the preprocessed file.

Thank you.

Robert






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