30 lines
1.4 KiB
ReStructuredText
30 lines
1.4 KiB
ReStructuredText
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=========================================
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C++ exceptions for long control transfers
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=========================================
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Normally Duktape uses ``setjmp()`` / ``longjmp()`` or their variants for
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internal long control transfers. One downside of these functions is that
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C++ automatic destructors (scope-based resource management, SBRM, a special
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case of RAII) in Duktape/C functions won't be executed which is awkward for
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C++ programmers.
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When ``DUK_USE_CPP_EXCEPTIONS`` is defined, and both Duktape and application
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code is compiled using a C++ compiler, Duktape uses C++ ``try-catch`` and
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``throw`` for internal long control transfers. This allows automatic
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destructors to run as expected. The config option is not enabled by default
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because C++ exceptions are sometimes disabled even when a C++ compiler is
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used (e.g. for performance reasons).
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The ``cpp_exceptions.cpp`` example illustrates how C++ exceptions can be
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used in Duktape/C functions at the moment:
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* Duktape uses C++ try/catch/throw internally; this is not visible to user
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code directly.
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* Automatic destructors (scope-based resource management) work as expected.
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* C++ exceptions can be used in Duktape/C functions normally, but user
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exceptions must be caught before they reach Duktape. If this is not
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done, such exceptions are caught by Duktape and converted to API errors
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(in other words, they won't propagate "through" Duktape at the moment).
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