[PATCH] D28832: Improve redefinition errors pointing to the same header.

[Vassil Vassilev via Phabricator via cfe-commits]

v.g.vassilev added a comment.

Here is an example that we recently had where we would be very happy to see better diagnostics:

  MessageTypes.h:
  
  #ifndef ROOT_MessageTypes
  #define ROOT_MessageTypes
  
  enum EMessageTypes {
     kROOTD_OPEN           = 2004,         //filename follows + mode
  };
  
  #endif
  
  module.modulemap:
  
  module "libNet.so" {
    requires cplusplus
    module "TMessage.h" { header "TMessage.h" export * }
    module "TNetFile.h" { header "TNetFile.h" export * }
    export *
  }
  
  Output:
  
  TNetFile.cxx:1:10: remark: building module 'libNet.so' as '/home/teemperor/Downloads/merge_enum/pcms/3MNDY7KURXTXS/libNet.so-141H35WZHCMDE.pcm' [-Rmodule-build]
  #include "TNetFile.h"
           ^
  TNetFile.cxx:1:10: remark: finished building module 'libNet.so' [-Rmodule-build]
  TNetFile.cxx:2:10: error: declaration of 'kROOTD_OPEN' must be imported from module 'libNet.so.TMessage.h' before it is required
  auto v = kROOTD_OPEN;
           ^
  In module 'libNet.so' imported from TNetFile.cxx:1:
  ./MessageTypes.h:5:4: note: previous declaration is here
     kROOTD_OPEN           = 2004,         //filename follows + mode
     ^
  1 error generated.
  
  test.sh:
  
  #!/bin/bash
  
  CLANG="/opt/clang/inst/bin/clang"
  
  rm -rf ./pcms/
  # Normal clang invocation
  #"$CLANG" -cc1 -triple x86_64-apple-macosx10.11.0 -fsyntax-only -I . -std=c++11 -x c++ TNetFile.cxx -nostdsysteminc
  # Modules clang invocation
  "$CLANG" -cc1 -triple x86_64-apple-macosx10.11.0 -fsyntax-only -I . -std=c++11  -fmodules  -fimplicit-module-maps -fmodules-cache-path=./pcms/ -fcolor-diagnostics -fdiagnostics-show-option -fdiagnostics-show-note-include-stack -x c++ TNetFile.cxx -nostdsysteminc -Rmodule-build
  
  TMessage.h:
  
  #ifndef ROOT_TMessage
  #define ROOT_TMessage
  #include "MessageTypes.h"
  #endif
  
  TNetFile.cxx:
  
  #include "TNetFile.h"
  auto v = kROOTD_OPEN;
  
  TNetFile.h:
  
  #ifndef ROOT_TNetFile
  #define ROOT_TNetFile
  #include "MessageTypes.h"
  #endif


https://reviews.llvm.org/D28832