Clang ASan fails when handling exceptions in try/catch block on Windows (AddressSanitizer: access-violation on unknown address)

Setup: Windows 10, Clang 16.0.3, ASan (-fsanitize=address), -O0

Any code related to handling exceptions e.g., try/catch, will result in a report about access-violation (additionally undefined sanitazation also would not be happy about it) or will change the behaviour of the program.

#include <stdexcept>
#include <iostream>

int main() {
    try {
        throw std::runtime_error("test");
    } catch (const std::runtime_error &ex) {
        std::cout << ex.what() << std::endl;
    }
    return 0;
}

Any variation from this list const std::runtime_error &ex, const std::runtime_error ex, std::runtime_error &ex, std::runtime_error ex result is some sort of bad behavior.

const std::runtime_error &ex, const std::runtime_error ex result directly in ASan error report like this:

==4384==ERROR: AddressSanitizer: access-violation on unknown address 0x00000000000e (pc 0x7ff74e3d12ca bp 0x008e4edcfaf0 sp 0x008e4edcd7f0 T0)
==4384==The signal is caused by a READ memory access.
==4384==Hint: address points to the zero page.
    #0 0x7ff74e3d12c9 in main C:\projects\test\asan.cpp:8
    #1 0x7ff74e478ccf in _CallSettingFrame d:\a01\_work\s\src\vctools\crt\vcruntime\src\eh\amd64\handlers.asm:49
    #2 0x7ff74e46e6bb in __FrameHandler3::CxxCallCatchBlock(struct _EXCEPTION_RECORD *) d:\a01\_work\s\src\vctools\crt\vcruntime\src\eh\frame.cpp:1521
    #3 0x7fffdfbb1715  (C:\WINDOWS\SYSTEM32\ntdll.dll+0x1800a1715)
    #4 0x7ff74e3d113b in main C:\projects\test\asan.cpp:6
    #5 0x7ff74e435d6b in invoke_main d:\a01\_work\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:78
    #6 0x7ff74e435d6b in __scrt_common_main_seh d:\a01\_work\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288
    #7 0x7fffdf757613  (C:\WINDOWS\System32\KERNEL32.DLL+0x180017613)
    #8 0x7fffdfb626b0  (C:\WINDOWS\SYSTEM32\ntdll.dll+0x1800526b0)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: access-violation C:\projects\test\asan.cpp:8 in main
==4384==ABORTING

While std::runtime_error &ex, std::runtime_error ex have altered behaviour and will contain some gibberish with a potential error report:

HГ─@]├HН♣▌f
=================================================================
==23388==ERROR: AddressSanitizer: attempting free on address which was not malloc()-ed: 0x7ff72ef69186 in thread T0
    #0 0x7ff72eed1e1d in free C:\src\llvm_package_16.0.3\llvm-project\compiler-rt\lib\asan\asan_malloc_win.cpp:82

Address 0x7ff72ef69186 is a wild pointer inside of access range of size 0x000000000001.
SUMMARY: AddressSanitizer: bad-free C:\src\llvm_package_16.0.3\llvm-project\compiler-rt\lib\asan\asan_malloc_win.cpp:82 in free
==23388==ABORTING

I've spent a lot of time thying to find the source of the error, but could not find anything. The only clue is that compiling without address sanitazation fixes everything.

There is a correspoding issue #749 in google/sanitizers, which is the home for LLVM Sanitizers.

The suggested workaround is

> to apply __attribute__((no_sanitize_address)) to every function that uses EH, and if your application doesn't use EH in normal operation, things will work.

But this defeats the point of the sanitization IMHO, so the slightly better workaround would be to wrap the try/catch in a lambda expression and call it immideately. The benefit is that we can apply __attribute__((no_sanitize_address)) specifically to that portion of the code thus limit the impact:

#include <stdexcept>
#include <iostream>

int main() {
    []() __attribute__((no_sanitize_address)) {
        try {
            throw std::runtime_error("test");
        } catch (const std::runtime_error &ex) {
            std::cout << ex.what() << std::endl;
        }
    }();
    return 0;
}

Now, let's make it more aesthetically pleasing by defining a macro that achieves the same functionality

#define TRY_CATCH_WRAPPER(code) []() __attribute__((no_sanitize_address)){code}();

But also let's not forget that this fails only windows when compiled with ASan

#ifdef __has_feature
#  if __has_feature(address_sanitizer)
#    define ASAN_ENABLED 1
#  endif
#endif


#if ASAN_ENABLED && (defined(_WIN64) || defined(_WIN32))
#  define TRY_CATCH_WRAPPER(code) []() __attribute__((no_sanitize_address)){code}();
#else
#  define TRY_CATCH_WRAPPER(code) code
#endif

Aaaand let's also make it more seamless to use by allowing lambda to capture variables by reference implicitly + it seems like a good practice to reference the issue

#ifdef __has_feature
#  if __has_feature(address_sanitizer)
#    define ASAN_ENABLED 1
#  endif
#endif


#if ASAN_ENABLED && (defined(_WIN64) || defined(_WIN32))
/* SEE: https://github.com/google/sanitizers/issues/749 */
#  define TRY_CATCH_WRAPPER(code) [&]() __attribute__((no_sanitize_address)){code}();
#else
#  define TRY_CATCH_WRAPPER(code) code
#endif

In the end we can use this like that:

#include <stdexcept>
#include <iostream>

#ifdef __has_feature
#  if __has_feature(address_sanitizer)
#    define ASAN_ENABLED 1
#  endif
#endif

#if ASAN_ENABLED && (defined(_WIN64) || defined(_WIN32))
/* SEE: https://github.com/google/sanitizers/issues/749 */
#  define TRY_CATCH_WRAPPER(code) [&]() __attribute__((no_sanitize_address)){code}();
#else
#  define TRY_CATCH_WRAPPER(code) code
#endif

void sub_main() {
    throw std::runtime_error("Hello, Sailor!");
}

int main() {
    int return_code = 0;

    TRY_CATCH_WRAPPER({
        try {
            sub_main();
            return_code = 0;
        } catch (const std::runtime_error &exc) {
            std::cout << exc.what() << std::endl;
            return_code = 1;
        }
    })

    return return_code;
}

And the exception is handled without any problems, hooray!

>! Note: the {} is not necessary when using TRY_CATCH_WRAPPER as the code is already wrapped in {} inside of the macro, but it is nicer with clang-format, so I go with it.