Replace NO_IMPLICIT_EXTERN_C with SYSTEM_IMPLICIT_EXTERN_C.

	gcc/
	Replace NO_IMPLICIT_EXTERN_C with SYSTEM_IMPLICIT_EXTERN_C.
	* doc/cpp.texi: Update comment.
	* doc/tm.texi: Rebuilt.
	* doc/tm.texi.in (NO_IMPLICIT_EXTERN_C): Replace with ...
	(SYSTEM_IMPLICIT_EXTERN_C): ... this, opposite sense.
	* doc/extend.texi (Backwards Compatibility): Clarify it is system
	headers affected by extern "C".
	* system.h: Poison NO_IMPLICIT_EXTERN_C.
	* config/alpha/alpha.h, config/arm/uclinux-elf.h,
	config/bfin/elf.h, config/cris/cris.h, config/darwin.h,
	config/dragonfly.h, config/freebsd.h, config/gnu-user.h,
	config/i386/cygming.h, config/i386/djgpp.h, config/i386/nto.h,
	config/ia64/hpux.h, config/lm32/lm32.h, config/lm32/uclinux-elf.h,
	config/lynx.h, config/mips/elf.h, config/mmix/mmix.h,
	config/netbsd.h, config/pa/pa-hpux.h, config/powerpcspe/sysv4.h,
	config/riscv/elf.h, config/rs6000/sysv4.h, config/rtems.h,
	config/s390/tpf.h, config/sh/newlib.h, config/sol2.h,
	config/sparc/openbsd64.h, config/sparc/sp-elf.h,
	config/sparc/sp64-elf.h, config/spu/spu.h,
	config/stormy16/stormy16.h, config/v850/v850.h,
	config/visium/visium.h, config/vx-common.h, config/xtensa/elf.h: Don't
	define NO_IMPLICIT_EXTERN_C.
	* config/rs6000/aix.h: Set SYSTEM_IMPLICIT_EXTERN_C.

	gcc/c-family/
	* c-lex.c (fe_file_change): Check SYSTEM_IMPLICIT_EXTERN_C not
	NO_IMPLICIT_EXTERN_C.

	gcc/cp/
	* cp/decl.c (decls_match): Check SYSTEM_IMPLICIT_EXTERN_C not
	NO_IMPLICIT_EXTERN_C.
	* cp/parser.c (cp_parser_parameter_declaration_clause): Likewise.

From-SVN: r262437

4 files changed, 10 insertions, 12 deletions

diff --git a/gcc/doc/cpp.texi b/gcc/doc/cpp.texi
index 4297c0c..3f7a8fc 100644
--- a/gcc/doc/cpp.texi
+++ b/gcc/doc/cpp.texi
@@ -3735,7 +3735,7 @@ so certain warnings should be suppressed.
 @item 4
 This indicates that the following text should be treated as being
 wrapped in an implicit @code{extern "C"} block.
-@c maybe cross reference NO_IMPLICIT_EXTERN_C
+@c maybe cross reference SYSTEM_IMPLICIT_EXTERN_C
 @end table
 
 As an extension, the preprocessor accepts linemarkers in non-assembler
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index 071d0ff..c7745c4 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -23475,7 +23475,7 @@ deprecated.   @xref{Deprecated Features}.
 
 @item Implicit C language
 Old C system header files did not contain an @code{extern "C" @{@dots{}@}}
-scope to set the language.  On such systems, all header files are
+scope to set the language.  On such systems, all system header files are
 implicitly scoped inside a C language scope.  Also, an empty prototype
 @code{()} is treated as an unspecified number of arguments, rather
 than no arguments, as C++ demands.
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index 1c5a809..057d650 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -11149,11 +11149,10 @@ Define this hook to return the name of a header file to be included at the start
 Define this hook to add target-specific C++ implicit extern C functions. If this function returns true for the name of a file-scope function, that function implicitly gets extern "C" linkage rather than whatever language linkage the declaration would normally have.  An example of such function is WinMain on Win32 targets.
 @end deftypefn
 
-@defmac NO_IMPLICIT_EXTERN_C
-Define this macro if the system header files support C++ as well as C@.
-This macro inhibits the usual method of using system header files in
-C++, which is to pretend that the file's contents are enclosed in
-@samp{extern "C" @{@dots{}@}}.
+@defmac SYSTEM_IMPLICIT_EXTERN_C
+Define this macro if the system header files do not support C++@.
+This macro handles system header files by pretending that system
+header files are enclosed in @samp{extern "C" @{@dots{}@}}.
 @end defmac
 
 @findex #pragma
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index bf2c64e..7579423 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -7657,11 +7657,10 @@ files @code{__STDC__} will always expand to 1.
 
 @hook TARGET_CXX_IMPLICIT_EXTERN_C
 
-@defmac NO_IMPLICIT_EXTERN_C
-Define this macro if the system header files support C++ as well as C@.
-This macro inhibits the usual method of using system header files in
-C++, which is to pretend that the file's contents are enclosed in
-@samp{extern "C" @{@dots{}@}}.
+@defmac SYSTEM_IMPLICIT_EXTERN_C
+Define this macro if the system header files do not support C++@.
+This macro handles system header files by pretending that system
+header files are enclosed in @samp{extern "C" @{@dots{}@}}.
 @end defmac
 
 @findex #pragma