Force user provided warning and error messages to only occupy one line.

 	PR 84195
gcc: 	* tree.c (escaped_string): New class.  Converts an unescaped
 	string into its escaped equivalent.
 	(warn_deprecated_use): Use the new class to convert the
 	deprecation message, if present.
 	(test_escaped_strings): New self test.
 	(test_c_tests): Add test_escaped_strings.
 	* doc/extend.texi (deprecated): Add a note that the
 	deprecation message is affected by the -fmessage-length
 	option, and that control characters will be escaped.
 	(#pragma GCC error): Document this pragma.
 	(#pragma GCC warning): Likewise.
 	* doc/invoke.texi (-fmessage-length): Document this option's
 	effect on the #warning and #error preprocessor directives and
 	the deprecated attribute.
	
testsuite;
 	* gcc.c-torture/compile/pr84195.c: New test.

From-SVN: r261633

gcc/ChangeLog

+2018-06-15  Nick Clifton  <nickc@redhat.com>
+
+	PR 84195
+	* tree.c (escaped_string): New class.  Converts an unescaped
+	string into its escaped equivalent.
+	(warn_deprecated_use): Use the new class to convert the
+	deprecation message, if present.
+	(test_escaped_strings): New self test.
+	(test_c_tests): Add test_escaped_strings.
+	* doc/extend.texi (deprecated): Add a note that the
+	deprecation message is affected by the -fmessage-length
+	option, and that control characters will be escaped.
+	(#pragma GCC error): Document this pragma.
+	(#pragma GCC warning): Likewise.
+	* doc/invoke.texi (-fmessage-length): Document this option's
+	effect on the #warning and #error preprocessor directives and
+	the deprecated attribute.
+
 2018-06-15  Richard Biener  <rguenther@suse.de>
 
 	* tree-vect-slp.c (vect_slp_bb): Dump MSG_OPTIMIZED_LOCATIONS

gcc/doc/extend.texi

@@ -2553,6 +2553,9 @@ present.
 The @code{deprecated} attribute can also be used for variables and
 types (@pxref{Variable Attributes}, @pxref{Type Attributes}.)
 
+The message attached to the attribute is affected by the setting of
+the @option{-fmessage-length} option.
+
 @item error ("@var{message}")
 @itemx warning ("@var{message}")
 @cindex @code{error} function attribute
@@ -6092,6 +6095,9 @@ The @code{deprecated} attribute can also be used for functions and
 types (@pxref{Common Function Attributes},
 @pxref{Common Type Attributes}).
 
+The message attached to the attribute is affected by the setting of
+the @option{-fmessage-length} option.
+
 @item nonstring
 @cindex @code{nonstring} variable attribute
 The @code{nonstring} variable attribute specifies that an object or member
@@ -7018,11 +7024,16 @@ warning is issued for line 4 because T2 is not explicitly
 deprecated.  Line 5 has no warning because T3 is explicitly
 deprecated.  Similarly for line 6.  The optional @var{msg}
 argument, which must be a string, is printed in the warning if
-present.
+present.  Control characters in the string will be replaced with
+escape sequences, and if the @option{-fmessage-length} option is set
+to 0 (its default value) then any newline characters will be ignored.
 
 The @code{deprecated} attribute can also be used for functions and
 variables (@pxref{Function Attributes}, @pxref{Variable Attributes}.)
 
+The message attached to the attribute is affected by the setting of
+the @option{-fmessage-length} option.
+
 @item designated_init
 @cindex @code{designated_init} type attribute
 This attribute may only be applied to structure types.  It indicates
@@ -21973,7 +21984,9 @@ compilation.
 @cindex pragma, diagnostic
 
 Prints @var{string} as a compiler message on compilation.  The message
-is informational only, and is neither a compilation warning nor an error.
+is informational only, and is neither a compilation warning nor an
+error.  Newlines can be included in the string by using the @samp{\n}
+escape sequence.
 
 @smallexample
 #pragma message "Compiling " __FILE__ "..."
@@ -21993,6 +22006,37 @@ TODO(Remember to fix this)
 prints @samp{/tmp/file.c:4: note: #pragma message:
 TODO - Remember to fix this}.
 
+@item #pragma GCC error @var{message}
+@cindex pragma, diagnostic
+Generates an error message.  This pragma @emph{is} considered to
+indicate an error in the compilation, and it will be treated as such.
+
+Newlines can be included in the string by using the @samp{\n}
+escape sequence.  They will be displayed as newlines even if the
+@option{-fmessage-length} option is set to zero.
+
+The error is only generated if the pragma is present in the code after
+pre-processing has been completed.  It does not matter however if the
+code containing the pragma is unreachable:
+
+@smallexample
+#if 0
+#pragma GCC error "this error is not seen"
+#endif
+void foo (void)
+@{
+  return;
+#pragma GCC error "this error is seen"
+@}
+@end smallexample
+
+@item #pragma GCC warning @var{message}
+@cindex pragma, diagnostic
+This is just like @samp{pragma GCC error} except that a warning
+message is issued instead of an error message.  Unless
+@option{-Werror} is in effect, in which case this pragma will generate
+an error as well.
+
 @end table
 
 @node Visibility Pragmas

gcc/doc/invoke.texi

@@ -3536,6 +3536,11 @@ Try to format error messages so that they fit on lines of about
 done; each error message appears on a single line.  This is the
 default for all front ends.
 
+Note - this option also affects the display of the @samp{#error} and
+@samp{#warning} pre-processor directives, and the @samp{deprecated}
+function/type/variable attribute.  It does not however affect the
+@samp{pragma GCC warning} and @samp{pragma GCC error} pragmas.
+
 @item -fdiagnostics-show-location=once
 @opindex fdiagnostics-show-location
 Only meaningful in line-wrapping mode.  Instructs the diagnostic messages

gcc/testsuite/ChangeLog

+2018-06-15  Nick Clifton  <nickc@redhat.com>
+
+	PR 84195
+	* gcc.c-torture/compile/pr84195.c: New test.
+
 2018-06-15  Richard Biener  <rguenther@suse.de>
 
 	PR middle-end/86159

gcc/testsuite/gcc.c-torture/compile/pr84195.c

+/* { dg-options "-Wdeprecated-declarations" } */
+
+/* Check that MSG is printed without the escape characters being interpreted.
+   Especially the newlines.
+
+   Note - gcc's behaviour is inconsistent in this regard as #error and
+   #warning will also display control characters as escape sequences,
+   whereas #pragma GCC error and #pragma GCC warning will perform the
+   control operations of the control characters.  */
+   
+#define MSG "foo\n\t\rbar"
+
+int f (int i __attribute__ ((deprecated (MSG))))
+{
+  return 0 ? i : 0; /* { dg-warning "'i' is deprecated: foo.n.t.rbar" } */
+}
+