converted to the execution character set, just like unescaped
characters.
+Unless the experimental @option{-fextended-identifiers} option is used,
GCC does not permit the use of characters outside the ASCII range, nor
-@samp{\u} and @samp{\U} escapes, in identifiers. We hope this will
-change eventually, but there are problems with the standard semantics
-of such ``extended identifiers'' which must be resolved through the
-ISO C and C++ committees first.
+@samp{\u} and @samp{\U} escapes, in identifiers. Even with that
+option, characters outside the ASCII range can only be specified with
+the @samp{\u} and @samp{\U} escapes, not used directly in identifiers.
@node Initial processing
@section Initial processing
part of the ``basic source character set'', at the implementation's
discretion (such as accented Latin letters, Greek letters, or Chinese
ideograms). This may be done with an extended character set, or the
-@samp{\u} and @samp{\U} escape sequences. GCC does not presently
-implement either feature in the preprocessor or the compiler.
+@samp{\u} and @samp{\U} escape sequences. The implementation of this
+feature in GCC is experimental; such characters are only accepted in
+the @samp{\u} and @samp{\U} forms and only if
+@option{-fextended-identifiers} is used.
As an extension, GCC treats @samp{$} as a letter. This is for
compatibility with some systems, such as VMS, where @samp{$} is commonly
These macros are defined, with value 1, if (and only if) the compilation
is for a target where @code{long int} and pointer both use 64-bits and
@code{int} uses 32-bit.
+
+@item __SSP__
+This macro is defined, with value 1, when @option{-fstack-protector} is in
+use.
+
+@item __SSP_ALL__
+This macro is defined, with value 2, when @option{-fstack-protector-all} is
+in use.
+
@end table
@node System-specific Predefined Macros
@chapter Other Directives
@findex #ident
+@findex #sccs
The @samp{#ident} directive takes one argument, a string constant. On
some systems, that string constant is copied into a special segment of
-the object file. On other systems, the directive is ignored.
+the object file. On other systems, the directive is ignored. The
+@samp{#sccs} directive is a synonym for @samp{#ident}.
-This directive is not part of the C standard, but it is not an official
-GNU extension either. We believe it came from System V@.
-
-@findex #sccs
-The @samp{#sccs} directive is recognized, because it appears in the
-header files of some systems. It is a very old, obscure, extension
-which we did not invent, and we have been unable to find any
-documentation of what it should do, so GCC simply ignores it.
+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@.
@cindex null directive
The @dfn{null directive} consists of a @samp{#} followed by a newline,
The C and C++ standards allow identifiers to be composed of @samp{_}
and the alphanumeric characters. C++ and C99 also allow universal
character names, and C99 further permits implementation-defined
-characters.
+characters. GCC currently only permits universal character names if
+@option{-fextended-identifiers} is used, because the implementation of
+universal character names in identifiers is experimental.
GCC allows the @samp{$} character in identifiers as an extension for
most targets. This is true regardless of the @option{std=} switch,
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