In C/C++, is there a directive similar to #ifndef for typedefs? -

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if want define value if not defined, :

#ifndef thing #define thing other_thing #endif

what if thing typedef'd identifier, , not defined? this: 

#ifntypedef thing_type typedef uint32_t thing_type #endif

the issue arose because wanted check see if external library has defined boolean type, i'd open hearing more general solution.

no there no such facility in c++ @ preprocessing stage. @ max can is

#ifndef thing_type #define thing_type uint32_t  #endif

though not coding practice , don't suggest it.


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