Strengthen exception specifications for stream types #3314
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strega-nil-ms
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Jan 3, 2023
strega-nil-ms
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Jan 4, 2023
StephanTLavavej
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Jan 21, 2023
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@strega-nil-ms FYI, I pushed a conflict-free merge with |
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I'm mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed. |
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Thanks for strengthening the STL! 🦾 🏋️ 📈 |
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This PR partially addresses #3278, but also strengthens exception specifications for some other functions. References to working draft are also updated to WG21-N4928.
Move assignment operators and
swapfunctions are generally marked withnoexcept. But I think move assignment operators ofbasic_filebufandbasic_(i|o)fstreamshouldn't benoexcept, because they callbasic_filebuf::closewhich may in turn call virtual functions that are possibly overridden. In other words, exception may be thrown from these move assignment operators.basic_syncbuf's should neither benoexceptdue to LWG-3498.Many move constructors remain non-
noexcept, because they need to copy-construct abasic_streambuf, and hence need to dynamically allocate storage forlocale. Maybe we should fix this in vNext.Currently EDG wrongly calculates
std::is_nothrow_move_assignable_v<std::osyncstream>andstd::is_nothrow_move_assignable_v<std::wosyncstream>asfalse, so these twostatic_asserts are skipped for EDG.