On Thu, 24 Mar 2016, Jeffrey Walton wrote:
Please forgive my ignorance... What is the "coexistence" that is discussed? Naively, I thought it would have been something like this contrived example: $ cat test.cxx #include <string> std::string foo __attribute__ ((visibility ("default"))); std::string bar __attribute__ ((visibility ("default"))); $ g++ -g3 -O2 -shared test.cxx -o test.so $ nm test.so | grep _Z3 ... 0000201c B _Z3barB5cxx11 00002034 B _Z3fooB5cxx11 $ echo _Z3fooB5cxx11 _Z3barB5cxx11 | c++filt foo[abi:cxx11] bar[abi:cxx11] foo bar In the above contrived example, foo and bar are in both namespaces. That is, the symbol coexists and "things just work".Consider the following example: markus@x4 /tmp % cat test.cpp #include <string> struct Test { __attribute__((used)) std::string foo() { return "foo"; }; }; markus@x4 /tmp % g++ -c test.cpp && nm test.o | grep _ZN4Test 0000000000000000 W _ZN4Test3fooB5cxx11Ev markus@x4 /tmp % clang++ -c test.cpp && nm test.o | grep _ZN4Test 0000000000000000 W _ZN4Test3fooEvExactly! How do I get both _ZN4Test3fooB5cxx11Ev and _ZN4Test3fooEv into the shared object so both GCC and Clang "just work". I thought that's what "coexistence" meant, but it appears to mean something else (that I have not been able to nail down).
You compile one object file using one compiler/ABI and another one using the other ABI, then link them both...
(sorry, I did try to argue against this whole situation but failed) -- Marc Glisse
