retval<T> to return a value and an error number at the same time #439
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Coldwings
reviewed
Apr 3, 2024
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| template<> inline | ||
| LogBuffer& operator << <void> (LogBuffer& log, const photon::retval<void>& v) { |
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Log on A successful retval breaks assertion in LogBuffer::operator<<(retval_base)
common/alog.h
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| @@ -508,6 +510,22 @@ struct ERRNO | |||
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| LogBuffer& operator << (LogBuffer& log, ERRNO e); | |||
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| inline LogBuffer& operator << (LogBuffer& log, const photon::retval_base& rvb) { | |||
| auto x = rvb._errno; | |||
| assert(0<x && x<INT_MAX); | |||
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assertion rejects x ==0 situation.
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so as to avoid some bugs:
unintentionally change the global errno by some function calls (e.g. printf or LOG_XXXX) in the error handling path, causing misunderstanding about the error
return an error but forget to set errno, causing incorrect handling of the error
In addition,
retval<T>makes the error number returned in register, more efficient than the global thread-localerrnovariable.