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The #error Directive

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Error directives produce compiler-time error messages.

#error token-string

The error messages include the argument token-string and are subject to macro expansion. These directives are most useful for detecting programmer inconsistencies and violation of constraints during preprocessing. The following example demonstrates error processing during preprocessing:

#if !defined(__cplusplus)
#error C++ compiler required.
#endif

When #error directives are encountered, compilation terminates.