A preprocessor undef directive causes the preprocessor to end the scope of a preprocessor definition.
If the identifier is not currently defined as a macro, #undef is ignored
Example of Usage
The following directives define BUFFER and SQR:
#define BUFFER 512 #define SQR(x) ((x) * (x))
The following directives nullify these definitions:
#undef BUFFER #undef SQR
Any occurrences of the identifiers BUFFER and SQR that follow these #undef directives are not replaced with any replacement tokens. Once the definition of a macro has been removed by an #undef directive, the identifier can be used in a new #define directive.
Preprocessor
Macros
Preprocessor
Directives
#define Preprocessor
Directive
List of Preprocessor
Directives
