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[Andreybokhanko <1488254@xxxxxxxxxxxxxxxxxx>]

Hi Stefan,

(In reply to comment #47)
> I think the attributes part of the patch is quite good compared with
> the mangling part... perhaps it should be split into a separate patch.
> 
> Regarding the mangling I'm not too happy with my patch. I don't understand 
> what most of the mangling code did before to actually know where 
> to insert the tagging code. This is C++ on a level I don't usually touch;
> I'm not familiar with all the terms (<unscoped-template-name>,
> <source-name>, ...) and just keep guessing what they do.
> 
> Also I don't like using recursion to determine the inherited abi tags;
> I think using temporary strings instead of directly writing to the stream
> would solve this.
> 
> All in all I hoped to get some feedbacks how things are done or should
> look like; I don't mind if someone else wants to take over and rewrite
> the mangling :)

Sure -- I will ask someone from Intel compiler team to handle mangling
part. We are co-located with Intel GCC team, so it's easy for us to ask
on intricacies of GCC implementation. :-)

I don't see attribute part of the patch to be reviewed, though -- we can
help with this as well. (Though the real authority to approve it belongs
to Aaron, so it's better to wait for his review (and ping if there is no
reply from his after a week)).

Yours,
Andrey

-- 
You received this bug notification because you are a member of Desktop
Packages, which is subscribed to llvm-toolchain-3.6 in Ubuntu.
https://bugs.launchpad.net/bugs/1488254

Title:
  clang++ no longer ABI-compatible with g++

Status in LLVM:
  Confirmed
Status in llvm-toolchain-3.6 package in Ubuntu:
  Confirmed

Bug description:
  $ cat foo.cc
  #include <string>
  std::string hello = "Hello, world!\n";
  $ cat bar.cc
  #include <string>
  #include <iostream>
  extern std::string hello;
  int main() {
      std::cout << hello;
      return 0;
  }
  $ g++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  Hello, world!
  $ clang++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  Hello, world!
  $ g++ -c foo.cc && clang++ foo.o bar.cc && ./a.out
  /tmp/bar-34fb23.o: In function `main':
  bar.cc:(.text+0x14): undefined reference to `hello'
  clang: error: linker command failed with exit code 1 (use -v to see invocation)
  $ clang++ -c foo.cc && g++ foo.o bar.cc && ./a.out
  /tmp/ccqU38Mh.o: In function `main':
  bar.cc:(.text+0x5): undefined reference to `hello[abi:cxx11]'
  collect2: error: ld returned 1 exit status

  In practice, this means that many programs using C++ libraries other
  than libstdc++ fail to compile with clang++. For example, mosh fails
  with undefined references to
  google::protobuf::internal::empty_string_,
  google::protobuf::MessageLite::InitializationErrorString() const, and
  google::protobuf::MessageLite::SerializeAsString() const.

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