problems catching std::runtime_error in a .so built with -fPIC

[Hasan Mahmood]

Hi,

I am having a problem trying to catch std::runtime_error (thrown from
libstdc++) in a .so I built with -fPIC. If I build without -fPIC, I
can catch the exception. Here is the code in the .so:

#include <locale>
#include <iostream>
#include <stdexcept>

#pragma GCC visibility push(default)

extern "C" void foo();

#pragma GCC visibility pop

void foo()
{
	try {
		std::locale loc("foo");
	} catch ( std::runtime_error const & e ) {
		std::cout << e.what() << "\n";
	}
}

Code in the program that loads the .so:

#include <dlfcn.h>
#include <iostream>

int main() {
	void * h = dlopen("./test.so", RTLD_NOW);
	if ( h ) {
		typedef void (*foo_func_type)();
		foo_func_type fn = (foo_func_type)dlsym(h, "foo");
		if ( !fn )
			std::cout << dlerror() << "\n";
		else
			fn();
	} else
		std::cout << dlerror() << "\n";
}

Here is the g++ command line for the .so:

g++ -shared -fPIC -fexceptions -frtti main.cpp

I thought at first that this was an issue with visibility of the
typeinfo for std::runtime_error, but then I found out that
std::runtime_error is marked "default" visibility in the stdexcept
header. An objdump of the .so has these symbols when built with -fPIC:

00002044 l     O .data  00000004              .hidden
DW.ref._ZTISt13runtime_error
00000000       O *UND*  0000000c              _ZTISt13runtime_error@@GLIBCXX_3.4

Without -fPIC, I get:

00000000       O *UND*  0000000c              _ZTISt13runtime_error@@GLIBCXX_3.4

Can anyone explain to me what is going on? How can I fix this or work
around it? Thanks.

Hasan.