Description of problem:

Compilation of scripts within root is broken

Version-Release number of selected component (if applicable):

root-5.34.32-8.fc24.x86_64

How reproducible:

Always

Steps to Reproduce:
1. Create a simple root script, e.g. the following as hello.C

#include <iostream>
void hello() {
   std::cout << "hello, world!" << endl;
}

2. .L hello.C++

Actual results:
Error: class,struct,union or type decltype(nullptr) not defined  /usr/include/c++/6.0.0/x86_64-redhat-linux/bits/c++config.h:2092:
Error: unrecognized language construct /usr/include/c++/6.0.0/bits/atomic_base.h:162:
Error: Symbol default is not defined in current scope  /usr/include/c++/6.0.0/bits/atomic_base.h:162:
Error: unrecognized language construct /usr/include/c++/6.0.0/bits/atomic_base.h:163:
Error: Symbol default is not defined in current scope  /usr/include/c++/6.0.0/bits/atomic_base.h:163:
Error: Symbol delete is not defined in current scope  /usr/include/c++/6.0.0/bits/atomic_base.h:164:
Error: Symbol delete is not defined in current scope  /usr/include/c++/6.0.0/bits/atomic_base.h:165:
Error: unrecognized language construct /usr/include/c++/6.0.0/bits/atomic_base.h:166:
Error: Symbol delete is not defined in current scope  /usr/include/c++/6.0.0/bits/atomic_base.h:166:
Error: Redefinition of default argument /usr/include/c++/6.0.0/bits/atomic_base.h:181:
Error: Redefinition of default argument /usr/include/c++/6.0.0/bits/atomic_base.h:198:
Error: Symbol bool is not defined in current scope  /usr/include/c++/6.0.0/bits/atomic_base.h:244:
Error: Function alignof(bool) is not defined in current scope  /usr/include/c++/6.0.0/bits/atomic_base.h:244:
Error: Invalid type 'constexpr' in declaration of 'int _S_alignment' /usr/include/c++/6.0.0/bits/atomic_base.h:244:
Syntax error /usr/include/c++/6.0.0/bits/atomic_base.h:246:
Error: unrecognized language construct /usr/include/c++/6.0.0/bits/atomic_base.h:246:
Error: unrecognized language construct /usr/include/c++/6.0.0/bits/atomic_base.h:249:
Error: Symbol default is not defined in current scope  /usr/include/c++/6.0.0/bits/atomic_base.h:249:
Error: unrecognized language construct /usr/include/c++/6.0.0/bits/atomic_base.h:250:
Error: Symbol default is not defined in current scope  /usr/include/c++/6.0.0/bits/atomic_base.h:250:
Error: Symbol delete is not defined in current scope  /usr/include/c++/6.0.0/bits/atomic_base.h:251:
Error: Symbol delete is not defined in current scope  /usr/include/c++/6.0.0/bits/atomic_base.h:252:
Error: unrecognized language construct /usr/include/c++/6.0.0/bits/atomic_base.h:253:
Error: Symbol delete is not defined in current scope  /usr/include/c++/6.0.0/bits/atomic_base.h:253:
Error: Redefinition of default argument /usr/include/c++/6.0.0/bits/atomic_base.h:380:
Error: Redefinition of default argument /usr/include/c++/6.0.0/bits/atomic_base.h:401:
Error: Redefinition of default argument /usr/include/c++/6.0.0/bits/atomic_base.h:420:
Error: Redefinition of default argument /usr/include/c++/6.0.0/bits/atomic_base.h:462:
Error: Redefinition of default argument /usr/include/c++/6.0.0/bits/atomic_base.h:506:
Error: Redefinition of default argument /usr/include/c++/6.0.0/bits/atomic_base.h:519:
Error: Redefinition of default argument /usr/include/c++/6.0.0/bits/atomic_base.h:529:
Error: Redefinition of default argument /usr/include/c++/6.0.0/bits/atomic_base.h:539:
Error: Redefinition of default argument /usr/include/c++/6.0.0/bits/atomic_base.h:549:
Error: Redefinition of default argument /usr/include/c++/6.0.0/bits/atomic_base.h:559:
Error: abstract class object '__atomic_base<bool> _M_base' declared /usr/include/c++/6.0.0/atomic:61:
Error: unrecognized language construct /usr/include/c++/6.0.0/atomic:64:
Error: Symbol default is not defined in current scope  /usr/include/c++/6.0.0/atomic:64:
Error: unrecognized language construct /usr/include/c++/6.0.0/atomic:65:
Error: Symbol default is not defined in current scope  /usr/include/c++/6.0.0/atomic:65:
Error: Symbol delete is not defined in current scope  /usr/include/c++/6.0.0/atomic:66:
Error: Symbol delete is not defined in current scope  /usr/include/c++/6.0.0/atomic:67:
Error: unrecognized language construct /usr/include/c++/6.0.0/atomic:68:
Error: Symbol delete is not defined in current scope  /usr/include/c++/6.0.0/atomic:68:
etc. etc. etc.

Expected results:

Should create a shared library with a function hello, which can be called from the command line. Works fine on Fedora 23 with 
libstdc++-devel-5.3.1-2.fc23.x86_64.

Additional info:

Alternatively, with rootcint and an empty LinkDef.h
> LinkDef.h
rootcint -f test.C -c -p LinkDef.h

gives the same messages. Note that removing the -p seems to work (i.e. using root's own preprocessor rather than the compiler's).