The following code reproduces the problem (g++ 4.2, Mac OS X 10.6):
// library.cpp: exports f(), compiled with -fno-rtti
#include <stdexcept>
#include <iostream>
extern "C" {
void f() {
try {
throw std::invalid_argument("std::exception handler");
} catch( std::exception& e) {
std::cout << e.what() << "\n";
} catch(...) {
std::cout << "... handler\n";
}
}
}
----------
// main.cpp: the main executable, dynamically loads the library
#include <dlfcn.h>
typedef void(*fPtr)();
int main() {
void* handle = dlopen( "./libexception_problem.dylib", RTLD_LAZY );
fPtr p_f = reinterpret_cast<fPtr>( dlsym( handle, "f" ) );
p_f();
}
----------
Output:
MacBook-Pro:teste pfranco$ # works fine with rtti
MacBook-Pro:teste pfranco$ g++ -c library.cpp && g++ -shared -o libexception_problem.dylib library.o && g++ main.cpp -o main && ./main
std::exception handler
MacBook-Pro:teste pfranco$ # breaks with -fno-rtti
MacBook-Pro:teste pfranco$ g++ -c -fno-rtti library.cpp && g++ -shared -o libexception_problem.dylib library.o && g++ -fno-rtti main.cpp -o main && ./main
... handler
MacBook-Pro:teste pfranco$ #-no_dead_strip_inits_and_terms doesn't change anything
MacBook-Pro:teste pfranco$ g++ -c -no_dead_strip_inits_and_terms -fno-rtti library.cpp && g++ -no_dead_strip_inits_and_terms -shared -o libexception_problem.dylib library.o && g++ -fno-rtti -no_dead_strip_inits_and_terms main.cpp -o main && ./main
... handler
MacBook-Pro:teste pfranco$ # linking against the shared library works, but this isn't always an option
MacBook-Pro:teste pfranco$ g++ -c -fno-rtti library.cpp && g++ -shared -o libexception_problem.dylib library.o && g++ -fno-rtti main.cpp -o main -L. -lexception_problem && ./main
std::exception handler
----------
This only happens if the code that throws is in a shared library, and only if the caught type is a base class of the actual exception - catch(std::invalid_argument&) works fine, std::logic_error& doesn't.
Interestingly, this doesn't happen on Linux (g++-4.4), even when running the exact same commands.
Questions:
1. Is this a bug, undefined behavior or by design?
2. How could I make it work, short of linking against the library?
Thanks a lot.
Pedro d'Aquino