D.2 Extensions Incompatible with ANSI C

• Unsigned preserving rules apply. (unsigned char and unsigned short promote to unsigned int .)

• Comments are converted to no spaces instead of a single space to allow token concatenation. (The compiler attempts to concatenate the two adjacent tokens.)

• All extern objects have file scope.

• Macro parameters are recognized and replaced within string or character constants in the macro definition.

• During macro replacement, an argument's preprocessing tokens are not macro replaced before the macro is expanded.

  If the name of a macro being replaced is found during the rescan of the replacement list, it is macro replaced.

• Support for predefined macro names that do not conform to the ANSI C Standard (that is, that do not start with two underscores or an underscore followed by a capital letter).

• A preprocessor directive is only recognized as such if the beginning # character occurs in the first column of a line. Any preprocessor directives preceded by white space are ignored.

• #ifdef is treated as "#if defined "

• #ifndef is treated as "#if !defined "

• Comments in macro replacement lists behave like ## operators when a valid token results after concatenation, except that adjoining white space is not deleted. If the resulting token is not valid, the comment in a macro replacement is deleted.

• Trigraphs are not recognized and replaced.