Return value from fail handler crash the program.

[yaoyuan1216]

@Naios

When I debug issue #46, I found another bug. It can be reproduced by the following code. I'd like to fix the bug, but have not caught the whole picture yet.

---

Expected Behavior

Finish normally.

Actual Behavior

Crashed at CTI_DETAIL_TRAP(); in macro CONTINUABLE_HAS_EXCEPTIONS.

Steps to Reproduce

make_exceptional_continuable<int>(supply_test_exception())
               .fail([](){ return 1; });

Your Environment

• OS: macOS Big Sur
• Compiler and version: Clang 11.0.3
• Standard library (if non default): {Please write here}

[Naios]

CTI_DETAIL_TRAP is platform implemented and will lead to this behaviour dependent on your platform:

/// Causes the application to exit abnormally
#if defined(_MSC_VER)
// NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
#define CTI_DETAIL_TRAP() __debugbreak()
#elif defined(__GNUC__)
// NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
#define CTI_DETAIL_TRAP() __builtin_trap()
#elif defined(__has_builtin) && __has_builtin(__builtin_trap)
// NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
#define CTI_DETAIL_TRAP() __builtin_trap()
#else
// NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
#define CTI_DETAIL_TRAP() *(volatile int*)0x11 = 0
#endif

The implementation of this macro aligns with the way how LLVM is handling traps.

The greater issue here is that the unhandled exception handler is called although you provided a handler in fail, however I was not reproduce this since your code runs fine for me:

TEST(regression_tests, fail_handler_called) {
  make_exceptional_continuable<int>(supply_test_exception()).fail([]() {
    return 1;
  });
}

Additionally this usage scenario has a test case already:

TYPED_TEST(single_dimension_tests, are_exceptions_partial_applyable) {

in continuable/test/unit-test/multi/test-continuable-base-errors.cpp

Maybe you left code from debugging that leads to this behaviour?

[yaoyuan1216]

@Naios yeah, you are right. I neglected one line code. auto continuable = make_exceptional_continuable<void>(supply_test_exception()); So sorry!