Re: clang++ and a modern C++ library

[Juan Francisco Cantero Hurtado]

On Sun, Nov 30, 2014 at 03:40:58PM -0800, Dave Huseby wrote:
> 
> Status update...
> 
> I've been working on porting Rust over to OpenBSD by building a Rust
> cross-compiler for Linux that can target i386-unknown-openbsd and
> x86_64-unknown-openbsd.  The largest roadblock on OpenBSD is the lack
> of a more recent GNU linker (ld).  I have tried the 2.17 linker in the
> source tree and it doesn't work.  To catch everybody up, the rust
> compiler is built on LLVM and uses C++1x which requires a newer
> compiler.  I started by using 4.8.3 on OpenBSD but the old linker
> isn't working.
> 
> Somebody suggested using clang on OpenBSD, but it appears that the
> port for clang++ doesn't include libc++.  Is that correct?  So clang++
> doesn't have a new enough standard C++ library to do the job.  I've
> tried using clang++ with the libstdc++ that is part of the gcc 4.8.3
> port but I can't seem to figure out the magic set of parameters to
> clang++ to make it select the newer libstdc++ that is part of the gcc
> 4.8.3 port.
> 
> I'm starting to think that this may not be possible without some
> catching up on toolchains for OpenBSD.  And given the conservative
> nature of OpenBSD, it may be some time before the toolchains are
> "modern" enough to compile and link the Rust compiler.

Disclaimer: I know nothing about c++ :)

I used this program to test clang and c++11 (extracted from
https://solarianprogrammer.com/2013/01/17/building-clang-libcpp-ubuntu-linux/ ):

//Program to test the new C++11 regular expressions syntax
#include <iostream>
#include <regex>
#include <string>

using namespace std;

int main()
{
    string input;
    regex 
rr("((\\+|-)?[[:digit:]]+)(\\.(([[:digit:]]+)?))?((e|E)((\\+|-)?)[[:digit:]]+)?");
    //As long as the input is correct ask for another number
    while(true)
    {
        cout<<"Give me a real number!"<<endl;
        cin>>input;
        if(!cin) break;
        //Exit when the user inputs q
        if(input=="q")
            break;
        if(regex_match(input,rr))
            cout<<"float"<<endl;
        else
        {
            cout<<"Invalid input"<<endl;
        }
    }
}

I tried with llvm-3.5.20140228p18 (the clang package), g++-4.9.2 and
libstdc++-4.8.3, the next command:

clang++ -std=c++11 -I/usr/local/include -I/usr/local/include/c++/4.9.2
-I/usr/local/include/c++/4.9.2/x86_64-unknown-openbsd5.6 -I/usr/include
-L/usr/local/lib/gcc-lib/amd64-unknown-openbsd5.6/3.3.6 -L/usr/local/lib
-nostdinc++ -lestdc++ test.cc

Apparently everything works fine.



-- 
Juan Francisco Cantero Hurtado http://juanfra.info