Could not find C++ standard library

[wbhart]

We are getting the following error when trying to use Cxx on a Gentoo system (with a Julia source tree built at a commit that is known to work elsewhere with Cxx).

I am not at all able to guess what is going on. Do you have any idea what might be causing this issue?

while loading /home2/hannes/.julia/v0.6/Cxx/src/utils.jl, in expression starting on line 51
ERROR: LoadError: LoadError: InitError: Could not find C++ standard library
 in AddLinuxHeaderPaths(::Cxx.ClangCompiler) at /home2/hannes/.julia/v0.6/Cxx/src/initialization.jl:298
 in addStdHeaders at /home2/hannes/.julia/v0.6/Cxx/src/initialization.jl:322 [inlined]
 in #initialize_instance!#33(::Bool, ::Function, ::Cxx.ClangCompiler) at /home2/hannes/.julia/v0.6/Cxx/src/initialization.jl:354
 in __init__() at /home2/hannes/.julia/v0.6/Cxx/src/initialization.jl:370
 in include_from_node1(::String) at ./loading.jl:532
 in eval(::Module, ::Any) at ./boot.jl:236
 in require(::Symbol) at ./loading.jl:446
 in include_from_node1(::String) at ./loading.jl:532
 in eval(::Module, ::Any) at ./boot.jl:236
 in require(::Symbol) at ./loading.jl:446
during initialization of module Cxx
while loading /home2/hannes/.julia/v0.6/Cxx/src/Cxx.jl, in expression starting on line 166
while loading /home2/hannes/.julia/v0.6/Singular/src/Singular.jl, in expression starting on line 4

[wbhart]

It looks like the C++ includes it is looking for on Gentoo are in:

/usr/lib64/gcc/x86_64-pc-linux-gnu/4.9.4/include/g++-v4

[wbhart]

In fact we got Cxx working on our particular Gentoo machines (which have gcc 4.9.4) by overriding where the header files are set in initialization.jl, with:

addHeaderDir(C, "/usr/lib64/gcc/x86_64-pc-linux-gnu/4.9.4/include/g++-v4", kind = C_System)
addHeaderDir(C, "/usr/lib64/gcc/x86_64-pc-linux-gnu/4.9.4/include/g++-v4/x86_64-pc-linux-gnu", kind = C_System)

That probably gives enough information to come up with a solution for this issue, I think.

[JonathanAnderson]

I'm having an issue too with finding the C++ library on a centos system.

julia_release-0.6 git:release-0.6 ❯ ./julia
               _
   _       _ _(_)_     |  A fresh approach to technical computing
  (_)     | (_) (_)    |  Documentation: https://docs.julialang.org
   _ _   _| |_  __ _   |  Type "?help" for help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 0.6.0-rc3.0 (2017-06-07 11:53 UTC)
 _/ |\__'_|_|_|\__'_|  |
|__/                   |  x86_64-redhat-linux

julia> using OhMyREPL

julia> using Cxx
String["/opt/rh/devtoolset-3/root"]
ERROR: LoadError: InitError: Could not find C++ standard library
Stacktrace:
 [1] AddLinuxHeaderPaths(::Cxx.ClangCompiler) at /home/janders/.julia/v0.6/Cxx/src/initialization.jl:299
 [2] addStdHeaders at /home/janders/.julia/v0.6/Cxx/src/initialization.jl:323 [inlined]
 [3] #initialize_instance!#33(::Bool, ::Function, ::Cxx.ClangCompiler) at /home/janders/.julia/v0.6/Cxx/src/initialization.jl:355
 [4] __init__() at /home/janders/.julia/v0.6/Cxx/src/initialization.jl:371
 [5] include_from_node1(::String) at ./loading.jl:569
 [6] eval(::Module, ::Any) at ./boot.jl:235
 [7] _require(::Symbol) at ./loading.jl:483
 [8] require(::Symbol) at ./loading.jl:398
during initialization of module Cxx
while loading /home/janders/.julia/v0.6/Cxx/src/Cxx.jl, in expression starting on line 169

I added a println to show me the Prefixes in initialization.jl and Its finding devtoolset-3 instead of devtoolset-6. I tried adding the correct directory to ./deps/src/clang-3.9.1/lib/Driver/ToolChains.cpp and rebuilding and this doesn't work.

If I patch the following diff then everything works just fine.

--- a/src/initialization.jl
+++ b/src/initialization.jl
@@ -271,7 +271,8 @@ function AddLinuxHeaderPaths(C)


     CXXJL_ROOTDIR = get(ENV, "CXXJL_ROOTDIR", "/usr")
-    const Prefixes = [ CXXJL_ROOTDIR ]
+    const Prefixes = [ CXXJL_ROOTDIR, "/opt/rh/devtoolset-6/root/usr" ]

     LibDirs = (Int === Int64 ? X86_64LibDirs : X86LibDirs)
     Triples = (Int === Int64 ? X86_64Triples : X86Triples) 

I'm leaving this here to help others and since I'm not sure how to fix this issue in a robust way.

[lyon-fnal]

Hi - I have the same problem too. My gcc comes from an unusual place, but I have an environment variable. Like @JonathanAnderson 's solution, I had to change

const Prefixes = [ CXXJL_ROOTDIR ] 
# To
const Prefixes = [ CXXJL_ROOTDIR, ENV["GCC_FQ_DIR"] ]

Any way somehow make this part of the build?

[VPetukhov]

@wbhart Thank you for your suggestion! It doesn't work for me, but it helped to fix the problem (dirty ugly fix). ~/.julia/v0.6/Cxx/src/initialization.jl has function ScanLibDirForGCCTriple(base,triple), which tries to find gcc headers and throws the error. So, I replaced its whole content to hardcoded paths:

function ScanLibDirForGCCTriple(base,triple)
    VersionString = "6.4.0"
    Version = VersionNumber(VersionString)
    GccPath = "/usr/lib64/gcc/x86_64-pc-linux-gnu/6.4.0/"
    return (Version, VersionString, GccPath)
end

After that, I specified include paths, relative to GccPath by changing incpath value and replacing all push!(headers, ...) in CollectLinuxHeaderPaths function with my include paths. Particularly, for me it was:

incpath = Path * "/include"

push!(headers, (incpath, C_System))
push!(headers, (incpath * "/g++-v6/", C_System))
push!(headers, (incpath * "/g++-v6/x86_64-pc-linux-gnu/", C_System))

[Gnimuc]

Fixed in #448