Document dg-line directive

2017-05-23  Tom de Vries  <tom@codesourcery.com>

	* doc/sourcebuild.texi (Directives, Verify compiler message): Document
	dg-line directive.

From-SVN: r248376

gcc/ChangeLog

+2017-05-23  Tom de Vries  <tom@codesourcery.com>
+
+	* doc/sourcebuild.texi (Directives, Verify compiler message): Document
+	dg-line directive.
+
 2017-05-23  Jan Hubicka  <hubicka@ucw.cz>
 
 	* cgraphunit.c (symbol_table::process_new_functions): Update.

gcc/doc/sourcebuild.texi

@@ -1180,6 +1180,18 @@ associated with the bogus message.  It is usually used with @samp{xfail}
 to indicate that the message is a known problem for a particular set of
 targets.
 
+@item @{ dg-line @var{linenumvar} @}
+This DejaGnu directive sets the variable @var{linenumvar} to the line number of
+the source line.  The variable @var{linenumvar} can then be used in subsequent
+@code{dg-error}, @code{dg-warning}, @code{dg-message} and @code{dg-bogus}
+directives.  For example:
+
+@smallexample
+int a;   /* @{ dg-line first_def_a @} */
+float a; /* @{ dg-error "conflicting types of" @} */
+/* @{ dg-message "previous declaration of" "" @{ target *-*-* @} first_def_a @} */
+@end smallexample
+
 @item @{ dg-excess-errors @var{comment} [@{ target/xfail @var{selector} @}] @}
 This DejaGnu directive indicates that the test is expected to fail due
 to compiler messages that are not handled by @samp{dg-error},