C compiler diagnostics

Message types and applicable options

Each message description includes a Type and an Options field as follows:

Type: Indicates whether the message is a warning, an error, a fatal error, or a combination of error types (see below).
Options: Indicates which cc command options must be set for the message to appear. ``all'' implies that the message is independent of cc options.

The following paragraphs explain the differences between warnings messages, error messages, and fatal errors.

Warning messages, in which warning: appears after the file name and line number, provide useful information without interrupting compilation. They may diagnose a programming error, or a violation of C syntax or semantics, for which the compiler will nevertheless generate valid object code.

Error messages, in which error: appears after the file name and line number, will cause the cc command to fail. Errors occur when the compiler has diagnosed a serious problem that makes it unable to understand the program or to continue to generate correct object code. It will attempt to examine the rest of the program for other errors, however. The cc command will not link the program if the compiler diagnoses errors.

Fatal errors cause the compiler to stop immediately and return an error indication to the cc command. A fatal error message is prefixed with fatal:. Such messages typically apply to start-up conditions, such as being unable to find a source file.