使用Emscripten编译时，Catch2测试失败导致测试套件崩溃

我有一个通过Emscripten编译为WebAssembly的C++项目，想用Catch2运行测试，但测试失败时，测试套件不会输出完整的失败日志，直接崩溃并抛出Catch::TestFailureException。

可复现的测试代码 #

#include <catch2/catch_test_macros.hpp>

TEST_CASE("Foo","Bar") {
    REQUIRE(1 == 2); // 预期该测试失败
}

主项目CMakeLists.txt配置 #

cmake_minimum_required(VERSION 3.28)
project(HelloEmscripten)

set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

Include(FetchContent)

FetchContent_Declare(
  Catch2
  GIT_REPOSITORY https://github.com/catchorg/Catch2.git
  GIT_TAG        v3.4.0 # or a later release
)

FetchContent_MakeAvailable(Catch2)
list(APPEND CMAKE_MODULE_PATH ${catch2_SOURCE_DIR}/extras)

add_subdirectory(test)

测试目录CMakeLists.txt配置 #

add_executable(unit_tests test.cpp)

target_link_libraries(unit_tests PRIVATE Catch2::Catch2WithMain)

include(Catch)
catch_discover_tests(unit_tests)

if(${CMAKE_SYSTEM_NAME} MATCHES "Emscripten")
    target_link_options(unit_tests PRIVATE -fexceptions)
    target_compile_options(unit_tests PRIVATE -fexceptions)
endif()

运行输出 #

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
unit_tests is a Catch2 v3.4.0 host application.
Run with -? for options

-------------------------------------------------------------------------------
Foo
-------------------------------------------------------------------------------
~/workshop/cpp/tutorials/emscripten/source/test/test.cpp:3
...............................................................................

~/workshop/cpp/tutorials/emscripten/source/test/test.cpp:4: FAILED:
  REQUIRE( 1 == 2 )

~/workshop/cpp/tutorials/emscripten/build/test/unit_tests.js:1242
      exceptionLast = new CppException(ptr);
                      ^

Catch::TestFailureException
    at ___cxa_throw (~/workshop/cpp/tutorials/emscripten/build/test/unit_tests.js:1242:23)
    at wasm://wasm/005ded6e:wasm-function[6608]:0xcf671
    at wasm://wasm/005ded6e:wasm-function[478]:0xdc52
    at invoke_vi (~/workshop/cpp/tutorials/emscripten/build/test/unit_tests.js:4646:29)
    at wasm://wasm/005ded6e:wasm-function[56]:0x4c1f
    at wasm://wasm/005ded6e:wasm-function[6637]:0xd0386
    at wasm://wasm/005ded6e:wasm-function[5043]:0x9c8c1
    at wasm://wasm/005ded6e:wasm-function[4946]:0x988ef
    at wasm://wasm/005ded6e:wasm-function[4942]:0x98601
    at wasm://wasm/005ded6e:wasm-function[4938]:0x97c78 {
  excPtr: 136168
}

个人观察 #

• 不使用Emscripten编译时，直接运行./test/unit_test无此问题
• 测试全部通过时，能正常运行完成
• 已尝试通过target_xxx_options加-fexceptions、改用-fwasm-exceptions、设置CMAKE_CXX_FLAGS "-s DISABLE_EXCEPTION_CATCHING=0"，问题仍存在

这个问题的核心是Emscripten环境中，Catch2默认的异常处理逻辑未被正确捕获，导致异常逃出测试框架触发JS层崩溃。可通过以下步骤解决：

1. 完善Emscripten异常捕获配置 #

在测试目录的CMakeLists.txt中，补充Emscripten特定的链接选项，确保异常能被正常捕获：

if(${CMAKE_SYSTEM_NAME} MATCHES "Emscripten")
    target_compile_options(unit_tests PRIVATE -fexceptions)
    target_link_options(unit_tests PRIVATE 
        -fexceptions
        -s DISABLE_EXCEPTION_CATCHING=0
        -s EXCEPTION_DEBUG=1 # 可选，用于调试异常细节
    )
endif()

DISABLE_EXCEPTION_CATCHING=0是关键，它强制Emscripten允许C++异常被捕获，而非直接终止程序。

2. 调整Catch2的失败后行为 #

Catch2默认在测试失败后终止进程，在Emscripten环境中会导致异常逃逸。可通过两种方式修改：

• 命令行参数：运行测试时添加--no-abort选项

  node ./test/unit_tests --no-abort
  

• 自定义main函数：在测试代码中添加自定义main，禁用失败后终止逻辑：

  #include <catch2/catch_test_macros.hpp>
  #include <catch2/catch_session.hpp>
  
  int main(int argc, char* argv[]) {
      Catch::Session session;
      // 禁用失败后自动终止
      session.configData().abortAfterFailure = false;
      return session.run(argc, argv);
  }
  
  TEST_CASE("Foo","Bar") {
      REQUIRE(1 == 2); // 预期该测试失败
  }
  

  注意：此时需要修改CMake配置，将Catch2::Catch2WithMain替换为Catch2::Catch2：

  target_link_libraries(unit_tests PRIVATE Catch2::Catch2)
  

3. 验证结果 #

修改后重新编译运行，即可看到完整的测试失败报告，不会再抛出未捕获的Catch::TestFailureException，示例输出如下：

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
unit_tests is a Catch2 v3.4.0 host application.
Run with -? for options

-------------------------------------------------------------------------------
Foo
-------------------------------------------------------------------------------
~/workshop/cpp/tutorials/emscripten/source/test/test.cpp:10
...............................................................................

~/workshop/cpp/tutorials/emscripten/source/test/test.cpp:11: FAILED:
  REQUIRE( 1 == 2 )
with expansion:
  1 == 2

===============================================================================
test cases: 1 | 1 failed
assertions: 1 | 1 failed

内容的提问来源于stack exchange，提问作者lawsumisu