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[EH] Make std::terminate() work with EH #16921

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[EH] Make std::terminate() work with EH #16921

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[EH] Make std::terminate() work with EH
aheejin May 9, 2022
fae8337
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aheejin May 10, 2022
290f072
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aheejin May 10, 2022
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aheejin May 10, 2022
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12 changes: 12 additions & 0 deletions system/lib/libcxx/include/exception
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Original file line number Diff line number Diff line change
Expand Up @@ -45,7 +45,13 @@ unexpected_handler get_unexpected() noexcept;
typedef void (*terminate_handler)();
terminate_handler set_terminate(terminate_handler f ) noexcept;
terminate_handler get_terminate() noexcept;
#ifdef __USING_WASM_EXCEPTIONS__
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Might want to add a comment here, or just point people to libcxxabi for an explanation. Unless that's obvious enough?

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I was not sure if it would be OK to copy-paste the same comment four times. Did that anyway.

// In Wasm EH, a JS exception thrown by abort() is caught by 'noexcept' cleanup
// // from which std::__terminate is called again, causing an infinite loop
[[noreturn]] void terminate();
#else
[[noreturn]] void terminate() noexcept;
#endif

bool uncaught_exception() noexcept;
int uncaught_exceptions() noexcept; // C++17
Expand Down Expand Up @@ -128,7 +134,13 @@ _LIBCPP_NORETURN _LIBCPP_FUNC_VIS void unexpected();
typedef void (*terminate_handler)();
_LIBCPP_FUNC_VIS terminate_handler set_terminate(terminate_handler) _NOEXCEPT;
_LIBCPP_FUNC_VIS terminate_handler get_terminate() _NOEXCEPT;
#ifdef __USING_WASM_EXCEPTIONS__
// In Wasm EH, a JS exception thrown by abort() is caught by 'noexcept' cleanup
// // from which std::__terminate is called again, causing an infinite loop
_LIBCPP_NORETURN _LIBCPP_FUNC_VIS void terminate();
#else
_LIBCPP_NORETURN _LIBCPP_FUNC_VIS void terminate() _NOEXCEPT;
#endif

_LIBCPP_FUNC_VIS bool uncaught_exception() _NOEXCEPT;
_LIBCPP_FUNC_VIS _LIBCPP_AVAILABILITY_UNCAUGHT_EXCEPTIONS int uncaught_exceptions() _NOEXCEPT;
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12 changes: 12 additions & 0 deletions system/lib/libcxxabi/src/cxa_handlers.cpp
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Expand Up @@ -50,7 +50,13 @@ get_terminate() noexcept
}

void
#ifdef __USING_WASM_EXCEPTIONS__
// In Wasm EH, a JS exception thrown by abort() is caught by 'noexcept' cleanup
// from which std::__terminate is called again, causing an infinite loop
__terminate(terminate_handler func)
#else
__terminate(terminate_handler func) noexcept
#endif
{
#ifndef _LIBCXXABI_NO_EXCEPTIONS
try
Expand All @@ -71,7 +77,13 @@ __terminate(terminate_handler func) noexcept

__attribute__((noreturn))
void
#ifdef __USING_WASM_EXCEPTIONS__
// In Wasm EH, a JS exception thrown by abort() is caught by 'noexcept' cleanup
// from which std::terminate is called again, causing an infinite loop
terminate()
#else
terminate() noexcept
#endif
{
#if !defined(_LIBCXXABI_NO_EXCEPTIONS) && !defined(__USING_EMSCRIPTEN_EXCEPTIONS__)
// If there might be an uncaught exception
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6 changes: 6 additions & 0 deletions system/lib/libcxxabi/src/cxa_handlers.h
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Expand Up @@ -25,7 +25,13 @@ __unexpected(unexpected_handler func);

_LIBCXXABI_HIDDEN _LIBCXXABI_NORETURN
void
#ifdef __USING_WASM_EXCEPTIONS__
// In Wasm EH, a JS exception thrown by abort() is caught by 'noexcept' cleanup
// // from which std::__terminate is called again, causing an infinite loop
__terminate(terminate_handler func);
#else
__terminate(terminate_handler func) noexcept;
#endif

} // std

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18 changes: 18 additions & 0 deletions tests/test_core.py
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Expand Up @@ -1639,6 +1639,24 @@ class Polymorphic {virtual void member(){}};
}
''', 'exception caught: std::bad_typeid')

@with_both_eh_sjlj
def test_std_terminate(self):
# std::terminate eventually calls abort(), which is implemented with
# throwing a JS exception, which used to cause an infinite loop that
# exhausted the call stack. The reason is std::terminate is marked
# 'noexcept' in the upstream LLVM, which generates cleanuppads that call
# std::terminate in case of an unexpected second exception happens while
# aborting, and our abort() was considered as that second exception. We
# removed 'noexcept' from std::terminate signature when Wasm EH is enabled
# to avoid this issue.
err = self.do_run(r'''
#include <exception>
int main() {
std::terminate();
}
''', assert_returncode=NON_ZERO)
self.assertNotContained('Maximum call stack size exceeded', err)

def test_iostream_ctors(self):
# iostream stuff must be globally constructed before user global
# constructors, so iostream works in global constructors
Expand Down