Macros
- Constrained template macros
- Version macros
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	BOOST_OUTCOME_DISABLE_EXECINFOIf defined, disables the use of the <execinfo.h>header (or the win32 emulation).
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	BOOST_OUTCOME_NODISCARDHow to tell the compiler than the return value of a function should not be discarded without examining it. 
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	BOOST_OUTCOME_REQUIRES(...)A C++ 20 requires(...), if available.
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	BOOST_OUTCOME_SYMBOL_VISIBLEHow to mark throwable types as always having default ELF symbol visibility. 
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	BOOST_OUTCOME_THREAD_LOCALHow to mark variables as having thread local storage duration. 
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	BOOST_OUTCOME_THROW_EXCEPTION(expr)How to throw a C++ exception, or equivalent thereof. 
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	BOOST_OUTCOME_TRY(var, expr)Evaluate an expression which results in a type matching the ValueOrError<T, E>concept, assigningTto a variable calledvarif successful, immediately returningtry_operation_return_as(expr)from the calling function if unsuccessful.
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	BOOST_OUTCOME_TRYV(expr)/BOOST_OUTCOME_TRY(expr)Evaluate an expression which results in a type matching the ValueOrError<void, E>concept, continuing execution if successful, immediately returningtry_operation_return_as(expr)from the calling function if unsuccessful.
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	BOOST_OUTCOME_TRYX(expr)Evaluate an expression which results in a type matching the ValueOrError<T, E>concept, emitting theTif successful, immediately returningtry_operation_return_as(expr)from the calling function if unsuccessful.
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	BOOST_OUTCOME_USE_STD_IN_PLACE_TYPEHow to implement in_place_type_t<T>andin_place_type<T>.
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	BOOST_OUTCOME_USE_STD_IS_NOTHROW_SWAPPABLEHow to implement is_nothrow_swappable<T>.



