Same STL files with different compilers [closed] - c++

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There are two binary files obtained from the same source file: one compiled with clang++-3.6 and the other one with g++-4.8. In a call to a function from the stl (std::unique, in particular) gdb brings me to the same file: /usr/include/c++/4.8/bits/stl_algo.h.
I expected that the implementations would be different for each compiler though. Do clang and gcc share parts of their C++ implementations?

Answer 1

I expected that the implementations would be different for each compiler though. Do clang and gcc share parts of their C++ implementations?
It's not that they share the same C++ implementations, it is rather that both compilers link with the same standard c++ library by default on your system.
I presume you are on linux, almost all programs installed from package manager link against libstdc++ (provided by g++).
By default, even when compiling with clang++, libstdc++ is used, so when you include iostream for example, it uses the one from /usr/include/c++/4.8.
If you want to link against llvm c++ library, you need to install the "libc++-dev" package (name may vary depending on your distro) and compile using: -stdlib=libc++ (instead of the default: -stdlib=libstdc++).
example:
test.cpp:
#include <iostream>
int main(int argc, char *argv[])
{
std::cout << "Hello World!!!\n";
return 0;
}
compiling using:
$ clang++ -stdlib=libc++ -o test test.cpp
will use the header from /usr/include/c++/v1 (from llvm)
but compiling using:
$ clang++ -stdlib=libstdc++ -o test test.cpp
# or (assuming the default on your system is libstdc++)
$ clang++ -o test test.cpp
will use header from /usr/include/c++/4.8 (from g++)