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Support nested exceptions except std::exception_ptr
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std::current_exception() makes a copy of current exception object
into returned std::exception_ptr. So the tracking of the original
exception object and its stacktrace are lost.
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@huangqinjin
huangqinjin committed Mar 19, 2024
1 parent 33529e5 commit 036c9de
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Showing 2 changed files with 104 additions and 19 deletions.
92 changes: 78 additions & 14 deletions src/from_exception.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -9,15 +9,30 @@
#include <boost/stacktrace/safe_dump_to.hpp>
#include <windows.h>

extern "C" void** __cdecl __current_exception(); // exported from vcruntime.dll
#define _pCurrentException static_cast<PEXCEPTION_RECORD>(*__current_exception())

namespace {

constexpr std::size_t kStacktraceDumpSize = 4096;

struct thrown_info {
ULONG_PTR object;
char* dump;
};

struct exception_data {
char dump_buffer[kStacktraceDumpSize];
ULONG_PTR thrown_object = 0;
bool rethrow = false;
bool capture_stacktraces_at_throw = true;
unsigned count = 0;
thrown_info* info = nullptr;

~exception_data() {
HANDLE hHeap = GetProcessHeap();
for (unsigned i = 0; i < count; ++i) {
HeapFree(hHeap, 0, info[i].dump);
}
HeapFree(hHeap, 0, info);
}
};

thread_local exception_data data;
Expand All @@ -35,18 +50,66 @@ inline ULONG_PTR PER_PEXCEPTOBJ(PEXCEPTION_RECORD p) {
return p->ExceptionInformation[1];
}

unsigned current_cxx_exception_index() {
if (PEXCEPTION_RECORD current_cxx_exception = _pCurrentException) {
for (unsigned i = data.count; i > 0;) {
--i;
if (data.info[i].object == PER_PEXCEPTOBJ(current_cxx_exception)) {
return i;
}
}
}
return data.count;
}

bool is_processing_rethrow(PEXCEPTION_RECORD p) {
// Processing flow:
// 0. throw;
// 1. _CxxThrowException(pExceptionObject = nullptr)
// 2. VEH & SEH (may throw new c++ exceptions!)
// 3. __RethrowException(_pCurrentException)
// 4. VEH
if (PER_PEXCEPTOBJ(p) == 0) return true;
PEXCEPTION_RECORD current_cxx_exception = _pCurrentException;
if (current_cxx_exception == nullptr) return false;
return PER_PEXCEPTOBJ(p) == PER_PEXCEPTOBJ(current_cxx_exception);
}

LONG NTAPI veh(PEXCEPTION_POINTERS p) {
if (data.capture_stacktraces_at_throw && PER_IS_MSVC_EH(p->ExceptionRecord)) {
if (PER_PEXCEPTOBJ(p->ExceptionRecord) == 0) {
data.rethrow = true;
} else if (data.rethrow && PER_PEXCEPTOBJ(p->ExceptionRecord) == data.thrown_object) {
data.rethrow = false;
} else {
data.rethrow = false;
data.thrown_object = PER_PEXCEPTOBJ(p->ExceptionRecord);
if (data.capture_stacktraces_at_throw &&
PER_IS_MSVC_EH(p->ExceptionRecord) &&
!is_processing_rethrow(p->ExceptionRecord)) {
HANDLE hHeap = GetProcessHeap();
unsigned index = current_cxx_exception_index();
unsigned new_count = 1 + (index < data.count ? index + 1 : 0);

for (unsigned i = new_count; i < data.count; ++i) {
HeapFree(hHeap, 0, data.info[i].dump);
data.info[i].dump = nullptr;
}

const std::size_t kSkip = 4;
boost::stacktrace::safe_dump_to(kSkip, data.dump_buffer, kStacktraceDumpSize);
void* new_info;
if (data.info) {
new_info = HeapReAlloc(hHeap, HEAP_ZERO_MEMORY, data.info, sizeof(thrown_info) * new_count);
} else {
new_info = HeapAlloc(hHeap, HEAP_ZERO_MEMORY, sizeof(thrown_info) * new_count);
}
if (new_info) {
data.count = new_count;
data.info = (thrown_info*)new_info;
data.info[data.count - 1].object = PER_PEXCEPTOBJ(p->ExceptionRecord);
char*& dump_ptr = data.info[data.count - 1].dump;
if (dump_ptr == nullptr) {
dump_ptr = (char*)HeapAlloc(hHeap, 0, kStacktraceDumpSize);
}
if (dump_ptr != nullptr) {
const std::size_t kSkip = 4;
boost::stacktrace::safe_dump_to(kSkip, dump_ptr, kStacktraceDumpSize);
}
} else if (new_count <= data.count) {
data.count = new_count - 1;
HeapFree(hHeap, 0, data.info[data.count - 1].dump);
data.info[data.count - 1].dump = nullptr;
}
}
return EXCEPTION_CONTINUE_SEARCH;
Expand All @@ -63,7 +126,8 @@ struct veh_installer {
extern "C" {

BOOST_SYMBOL_EXPORT const char* boost_stacktrace_impl_current_exception_stacktrace() {
return data.capture_stacktraces_at_throw ? data.dump_buffer : nullptr;
unsigned index = current_cxx_exception_index();
return index < data.count ? data.info[index].dump : nullptr;
}

BOOST_SYMBOL_EXPORT bool* boost_stacktrace_impl_ref_capture_stacktraces_at_throw() {
Expand Down
31 changes: 26 additions & 5 deletions test/test_from_exception.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -42,6 +42,18 @@ BOOST_NOINLINE BOOST_SYMBOL_VISIBLE void in_test_rethrow_1(const char* msg) {
}
}

BOOST_NOINLINE BOOST_SYMBOL_VISIBLE void in_test_rethrow_2(const char* msg) {
try {
in_test_throw_2(msg);
} catch (const std::exception&) {
try {
in_test_throw_1(msg);
} catch (const std::exception&) {}

throw;
}
}

BOOST_NOINLINE BOOST_SYMBOL_VISIBLE void test_no_exception() {
auto trace = stacktrace::from_current_exception();
BOOST_TEST(!trace);
Expand Down Expand Up @@ -70,13 +82,8 @@ BOOST_NOINLINE BOOST_SYMBOL_VISIBLE void test_after_other_exception() {
auto trace = stacktrace::from_current_exception();
BOOST_TEST(trace);
std::cout << "Tarce in test_after_other_exception(): " << trace;
#if defined(BOOST_MSVC)
BOOST_TEST(to_string(trace).find("in_test_throw_1") == std::string::npos);
BOOST_TEST(to_string(trace).find("in_test_throw_2") != std::string::npos);
#else
BOOST_TEST(to_string(trace).find("in_test_throw_1") != std::string::npos);
BOOST_TEST(to_string(trace).find("in_test_throw_2") == std::string::npos);
#endif
}
}

Expand All @@ -92,6 +99,19 @@ BOOST_NOINLINE BOOST_SYMBOL_VISIBLE void test_rethrow() {
}
}

BOOST_NOINLINE BOOST_SYMBOL_VISIBLE void test_rethrow_after_other_exception() {
try {
in_test_rethrow_2("test_rethrow_after_other_exception");
} catch (const std::exception&) {
auto trace = stacktrace::from_current_exception();
BOOST_TEST(trace);
std::cout << "Tarce in test_rethrow_after_other_exception(): " << trace << '\n';
BOOST_TEST(to_string(trace).find("in_test_throw_1") == std::string::npos);
BOOST_TEST(to_string(trace).find("in_test_throw_2") != std::string::npos);
BOOST_TEST(to_string(trace).find("in_test_rethrow_2") != std::string::npos);
}
}

BOOST_NOINLINE BOOST_SYMBOL_VISIBLE void test_nested() {
try {
in_test_throw_1("test_other_exception_active");
Expand Down Expand Up @@ -180,6 +200,7 @@ int main() {
test_trace_from_exception();
test_after_other_exception();
test_rethrow();
test_rethrow_after_other_exception();
test_nested();
test_rethrow_nested();
test_from_other_thread();
Expand Down

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