Diagnostics - Red Hat ENTERPRISE LINUX 3 - USING CPP Using Instructions

Chapter 5.

Diagnostics

The directive causes the preprocessor to report a fatal error. The tokens forming the rest of
#error
the line following are used as the error message.
#error
You would use inside of a conditional that detects a combination of parameters which you
#error
know the program does not properly support. For example, if you know that the program will not run
properly on a VAX, you might write
#ifdef __vax__
#error "Won't work on VAXen. See comments at get_last_object."
#endif
If you have several configuration parameters that must be set up by the installation in a consistent way,
you can use conditionals to detect an inconsistency and report it with . For example,
#error
#if !defined(UNALIGNED_INT_ASM_OP) && defined(DWARF2_DEBUGGING_INFO)
#error "DWARF2_DEBUGGING_INFO requires UNALIGNED_INT_ASM_OP."
#endif
The directive is like , but causes the preprocessor to issue a warning and continue
#warning #error
preprocessing. The tokens following are used as the warning message.
#warning
You might use in obsolete header files, with a message directing the user to the header file
#warning
which should be used instead.
Neither nor macro-expands its argument. Internal whitespace sequences are each
#error #warning
replaced with a single space. The line must consist of complete tokens. It is wisest to make the ar-
gument of these directives be a single string constant; this avoids problems with apostrophes and the
like.