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title: "#error Directive (C/C++) | Microsoft Docs"
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---
# #error Directive (C/C++)
The `#error` directive emits a user-specified error message at compile time and then terminates the compilation.  
  
## Syntax  
  
```  
#errortoken-string  
```  
  
## Remarks  
 The error message that this directive emits includes the *token-string* parameter. The `token-string` parameter is not subject to macro expansion. This directive is most useful during preprocessing for notifying the developer of a program inconsistency or the violation of a constraint. The following example demonstrates error processing during preprocessing:  
  
```  
#if !defined(__cplusplus)  
#error C++ compiler required.  
#endif  
```  
  
## See Also  
 [Preprocessor Directives](../preprocessor/preprocessor-directives.md)