9.5.7 Line directives

Line directives can be used to alter the line numbers and source file names that are reported by the compiler in output such as warnings and errors.

[Note: Line directives are most commonly used in meta-programming tools that generate C# source code from some other text input. end note]

pp-line::

whitespace_opt # whitespace_opt line whitespace line-indicator pp-new-line

line-indicator::

decimal-digits whitespace file-name

decimal-digits

identifier-or-keyword

file-name::

" file-name-characters "

file-name-characters::

file-name-character

file-name-characters file-name-character

file-name-character::

Any character except " (U+0022), and new-line-character

When no #line directives are present, the compiler reports true line numbers and source file names in its output. When processing a #line directive that includes a line-indicator that is not identifier-or-keyword, the compiler treats the line after the directive as having the given line number (and file name, if specified).

A #line directive in which the line-indicator is an identifier-or-keyword whose value equals default (using equality as specified in §9.4.2) reverses the effect of all preceding #line directives. The compiler reports true line information for subsequent lines, precisely as if no #line directives had been processed.

The purpose of a line-indicator with an identifier-or-keyword whose value does not equal default is implementation-defined. An implementation that does not recognize such an identifier-or-keyword in a lineindicator shall issue a warning.

[Note: Note that a file-name differs from a regular string literal in that escape characters are not processed; the '\' character simply designates an ordinary back-slash character within a file-name. end note]