I modified the 'jump.cpp' example and added the line marked CRASH in f1() #include <cstdlib> #include <cstring> #include <iostream> #include <vector> #include <boost/assert.hpp> #include <boost/context/all.hpp> namespace ctx = boost::ctx; ctx::fcontext_t fcm, fc1, fc2; void f1( intptr_t) { std::cout<<"hello "<<0; // WORKS printf( "hello %d", 0 ); // <<< CRASH std::cout << "f1: entered" << std::endl; std::cout << "f1: call jump_fcontext( & fc1, & fc2, 0)" << std::endl; ctx::jump_fcontext( & fc1, & fc2, 0); std::cout << "f1: return" << std::endl; ctx::jump_fcontext( & fc1, & fcm, 0); } void f2( intptr_t) { std::cout << "f2: entered" << std::endl; std::cout << "f2: call jump_fcontext( & fc2, & fc1, 0)" << std::endl; ctx::jump_fcontext( & fc2, & fc1, 0); BOOST_ASSERT( false && ! "f2: never returns"); } int main( int argc, char * argv[]) { ctx::stack_allocator alloc1, alloc2; fc1.fc_stack.base = alloc1.allocate(ctx::minimum_stacksize()); fc1.fc_stack.limit = static_cast< char * >( fc1.fc_stack.base) - ctx::minimum_stacksize(); ctx::make_fcontext( & fc1, f1); fc2.fc_stack.base = alloc2.allocate(ctx::minimum_stacksize()); fc2.fc_stack.limit = static_cast< char * >( fc2.fc_stack.base) - ctx::minimum_stacksize(); ctx::make_fcontext( & fc2, f2); std::cout << "main: call start_fcontext( & fcm, & fc1, 0)" << std::endl; ctx::jump_fcontext( & fcm, & fc1, 0); std::cout << "main: done" << std::endl; return EXIT_SUCCESS; }