libcpp

	PR preprocessor/22168:
	* include/cpplib.h (struct cpp_options) <objc>: Update
	documentation.
	* expr.c (eval_token): Warn for use of assertions.
	* directives.c (directive_diagnostics): Warn about extensions.
	(DEPRECATED): New define.
	(DIRECTIVE_TABLE): Use it.
gcc
	PR preprocessor/22168:
	* doc/cpp.texi (Top): Update menu.
	(Alternatives to Wrapper #ifndef): New node.
	(Other Directives): Document deprecation.
	(Obsolete Features): Remove menu.
	(Assertions): Merge node into Obsolete Features.
	(Obsolete once-only headers): Move earlier; rename to Alternatives
	to Wrapper #ifndef.
	* doc/cppopts.texi: Update.
	* c.opt (Wdeprecated): Enable for C and ObjC.
	* doc/invoke.texi (Option Summary): Move -Wno-deprecated.
	(C++ Dialect Options): Move -Wno-deprecated from here to...
	(Warning Options): ... here.
gcc/testsuite
	PR preprocessor/22168:
	* gcc.dg/pch/import-2.hs: Add -Wno-deprecated.
	* gcc.dg/pch/import-1.hs: Add -Wno-deprecated.
	* gcc.dg/pch/import-2.c: Add -Wno-deprecated.
	* gcc.dg/pch/import-1.c: Add -Wno-deprecated.
	* gcc.dg/cpp/import2.c: Add -Wno-deprecated.
	* gcc.dg/cpp/import1.c: Add -Wno-deprecated.
	* gcc.dg/cpp/trad/assert3.c: Add -Wno-deprecated.
	* gcc.dg/cpp/trad/assert2.c: Add -Wno-deprecated.
	* gcc.dg/cpp/trad/assert1.c: Add -Wno-deprecated.
	* gcc.dg/cpp/ident.c: Add -Wno-deprecated.
	* gcc.dg/cpp/ident-1.c: Add -Wno-deprecated.
	* gcc.dg/cpp/extratokens.c: Add -Wno-deprecated.
	* gcc.dg/cpp/assert3.c: Add -Wno-deprecated.
	* gcc.dg/cpp/assert2.c: Add -Wno-deprecated.
	* gcc.dg/cpp/assert1.c: Add -Wno-deprecated.
	* gcc.dg/cpp/assert4.c: Compile with -ansi and not -pedantic.  Add
	-Wno-deprecated.
	* gcc.dg/cpp/pr22168.c: New file.
	* gcc.dg/cpp/pr22168-2.c: New file.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@135264 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 44 insertions, 47 deletions

diff --git a/gcc/doc/cpp.texi b/gcc/doc/cpp.texi
index b98aef2bd68..9e2f19ad0b5 100644
--- a/gcc/doc/cpp.texi
+++ b/gcc/doc/cpp.texi
@@ -111,6 +111,7 @@ Header Files
 * Include Operation::
 * Search Path::
 * Once-Only Headers::
+* Alternatives to Wrapper #ifndef::
 * Computed Includes::
 * Wrapper Headers::
 * System Headers::
@@ -168,8 +169,7 @@ Implementation Details
 
 Obsolete Features
 
-* Assertions::
-* Obsolete once-only headers::
+* Obsolete Features::
 
 @end detailmenu
 @end menu
@@ -734,6 +734,7 @@ underscores in header file names, and at most one dot.
 * Include Operation::
 * Search Path::
 * Once-Only Headers::
+* Alternatives to Wrapper #ifndef::
 * Computed Includes::
 * Wrapper Headers::
 * System Headers::
@@ -959,6 +960,42 @@ begin with @samp{_}.  In a system header file, it should begin with
 file, the macro name should contain the name of the file and some
 additional text, to avoid conflicts with other header files.
 
+@node Alternatives to Wrapper #ifndef
+@section Alternatives to Wrapper #ifndef
+
+CPP supports two more ways of indicating that a header file should be
+read only once.  Neither one is as portable as a wrapper @samp{#ifndef}
+and we recommend you do not use them in new programs, with the caveat
+that @samp{#import} is standard practice in Objective-C.
+
+@findex #import
+CPP supports a variant of @samp{#include} called @samp{#import} which
+includes a file, but does so at most once.  If you use @samp{#import}
+instead of @samp{#include}, then you don't need the conditionals
+inside the header file to prevent multiple inclusion of the contents.
+@samp{#import} is standard in Objective-C, but is considered a
+deprecated extension in C and C++.
+
+@samp{#import} is not a well designed feature.  It requires the users of
+a header file to know that it should only be included once.  It is much
+better for the header file's implementor to write the file so that users
+don't need to know this.  Using a wrapper @samp{#ifndef} accomplishes
+this goal.
+
+In the present implementation, a single use of @samp{#import} will
+prevent the file from ever being read again, by either @samp{#import} or
+@samp{#include}.  You should not rely on this; do not use both
+@samp{#import} and @samp{#include} to refer to the same header file.
+
+Another way to prevent a header file from being included more than once
+is with the @samp{#pragma once} directive.  If @samp{#pragma once} is
+seen when scanning a header file, that file will never be read again, no
+matter what.
+
+@samp{#pragma once} does not have the problems that @samp{#import} does,
+but it is not recognized by all preprocessors, so you cannot rely on it
+in a portable program.
+
 @node Computed Includes
 @section Computed Includes
 @cindex computed includes
@@ -3467,6 +3504,8 @@ These directives are not part of the C standard, but they are not
 official GNU extensions either.  What historical information we have
 been able to find, suggests they originated with System V@.
 
+Both @samp{#ident} and @samp{#sccs} are deprecated extensions.
+
 @cindex null directive
 The @dfn{null directive} consists of a @samp{#} followed by a newline,
 with only whitespace (including comments) in between.  A null directive
@@ -4004,16 +4043,10 @@ may not be a limitation.
 @node Obsolete Features
 @section Obsolete Features
 
-CPP has a number of features which are present mainly for
-compatibility with older programs.  We discourage their use in new code.
-In some cases, we plan to remove the feature in a future version of GCC@.
+CPP has some features which are present mainly for compatibility with
+older programs.  We discourage their use in new code.  In some cases,
+we plan to remove the feature in a future version of GCC@.
 
-@menu
-* Assertions::
-* Obsolete once-only headers::
-@end menu
-
-@node Assertions
 @subsection Assertions
 @cindex assertions
 
@@ -4097,42 +4130,6 @@ no effect.
 You can also make or cancel assertions using command line options.
 @xref{Invocation}.
 
-@node Obsolete once-only headers
-@subsection Obsolete once-only headers
-
-CPP supports two more ways of indicating that a header file should be
-read only once.  Neither one is as portable as a wrapper @samp{#ifndef},
-and we recommend you do not use them in new programs.
-
-@findex #import
-In the Objective-C language, there is a variant of @samp{#include}
-called @samp{#import} which includes a file, but does so at most once.
-If you use @samp{#import} instead of @samp{#include}, then you don't
-need the conditionals inside the header file to prevent multiple
-inclusion of the contents.  GCC permits the use of @samp{#import} in C
-and C++ as well as Objective-C@.  However, it is not in standard C or C++
-and should therefore not be used by portable programs.
-
-@samp{#import} is not a well designed feature.  It requires the users of
-a header file to know that it should only be included once.  It is much
-better for the header file's implementor to write the file so that users
-don't need to know this.  Using a wrapper @samp{#ifndef} accomplishes
-this goal.
-
-In the present implementation, a single use of @samp{#import} will
-prevent the file from ever being read again, by either @samp{#import} or
-@samp{#include}.  You should not rely on this; do not use both
-@samp{#import} and @samp{#include} to refer to the same header file.
-
-Another way to prevent a header file from being included more than once
-is with the @samp{#pragma once} directive.  If @samp{#pragma once} is
-seen when scanning a header file, that file will never be read again, no
-matter what.
-
-@samp{#pragma once} does not have the problems that @samp{#import} does,
-but it is not recognized by all preprocessors, so you cannot rely on it
-in a portable program.
-
 @node Differences from previous versions
 @section Differences from previous versions
 @cindex differences from previous versions