> "Oliver Kowalke" <oliver.kowalke@xxxxxx> writes:
>
> > What marks the end of stack or how does uw_frame_state_for() detect the
> end of stack?
> > I've a coroutine library and I'm using _Unwind_ForcedUnwind() for stack
> cleanup. Function _Unwind_ForcedUnwind_Phase2() never sets
> _URC_END_OF_STACK!
>
> What happens when it goes past the top of the stack?
I get an segmentation fault from _Uwind_resume().
> Normally the unwinder returns _URC_END_OF_STACK when it finds a stack
> frame with a PC value with no associated FDE. A specific such PC value
> is zero.
In the example _URC_END_OF_STACK is not returned. A simple memory chunk is used as stack. Maybe I've to append a special page at the end of the stack - or something else?
I hopefuly the issue can be fixed.
best regards,
Oliver
test code with segfault:
#include <ucontext.h>
#include <unwind.h>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <vector>
static int counter = 0;
static ucontext_t ucf, ucm;
struct X
{
X()
{ std::cout << "X()" << std::endl; }
~X()
{ std::cout << "~X()" << std::endl; }
};
_Unwind_Reason_Code stop(
int version,
_Unwind_Action actions,
_Unwind_Exception_Class exc_class,
_Unwind_Exception *exc,
_Unwind_Context *context,
void * param) {
// std::cout << "counter == " << ++counter << std::endl;
if ( actions & _UA_END_OF_STACK) {
std::cout << "end of stack, jump back" << std::endl;
_Unwind_DeleteException( exc);
if ( ::swapcontext( & ucf, & ucm) == -1)
::abort();
}
return _URC_NO_REASON;
}
void force_unwind()
{
_Unwind_Exception * exc = new _Unwind_Exception;
std::memset( exc, 0, sizeof( * exc) );
_Unwind_ForcedUnwind( exc, stop, 0);
}
void f( int i) {
if ( i > 0) {
X x;
f( --i);
} else {
force_unwind();
std::cout << "fini" << std::endl;
}
}
int main( int argc, char * argv[]) {
std::vector< char > fn_stack(16384, '\0');
if ( ::getcontext( & ucf) == -1)
::abort();
ucf.uc_stack.ss_sp = & fn_stack[0];
ucf.uc_stack.ss_size = fn_stack.size();
::makecontext( & ucf, (void(*)())( f), 1, 5);
if ( ::swapcontext( & ucm, & ucf) == -1)
::abort();
std::cout << "done" << std::endl;
return 0;
}
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