Darwin, Objective-C: Support -fconstant-cfstrings [PR108743].

This support the -fconstant-cfstrings option as used by clang (and
expect by some build scripts) as an alias to the target-specific
-mconstant-cfstrings.

The documentation is also updated to reflect that the 'f' option is
only available on Darwin, and to add the 'm' option to the Darwin
section of the invocation text.

Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>

	PR target/108743

gcc/ChangeLog:

	* config/darwin.opt: Add fconstant-cfstrings alias to
	mconstant-cfstrings.
	* doc/invoke.texi: Amend invocation descriptions to reflect
	that the fconstant-cfstrings is a target-option alias and to
	add the missing mconstant-cfstrings option description to the
	Darwin section.

2 files changed, 24 insertions, 7 deletions

diff --git a/gcc/config/darwin.opt b/gcc/config/darwin.opt
index feaa958..d655aae 100644
--- a/gcc/config/darwin.opt
+++ b/gcc/config/darwin.opt
@@ -33,6 +33,10 @@ fapple-kext
 Target C++ Var(flag_apple_kext)
 Generate code for darwin loadable kernel extensions.
 
+fconstant-cfstrings
+ObjC ObjC++ Alias(mconstant-cfstrings)
+Generate compile-time CFString objects.
+
 iframework
 Target RejectNegative C ObjC C++ ObjC++ Joined Separate
 -iframework <dir>	Add <dir> to the end of the system framework include path.
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index efcf3bf..26bcbe2 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -4830,10 +4830,12 @@ and Objective-C++ programs:
 Use @var{class-name} as the name of the class to instantiate for each
 literal string specified with the syntax @code{@@"@dots{}"}.  The default
 class name is @code{NXConstantString} if the GNU runtime is being used, and
-@code{NSConstantString} if the NeXT runtime is being used (see below).  The
-@option{-fconstant-cfstrings} option, if also present, overrides the
-@option{-fconstant-string-class} setting and cause @code{@@"@dots{}"} literals
-to be laid out as constant CoreFoundation strings.
+@code{NSConstantString} if the NeXT runtime is being used (see below).  On
+Darwin (macOS, MacOS X) platforms, the @option{-fconstant-cfstrings} option, if
+also present, overrides the @option{-fconstant-string-class} setting and cause
+@code{@@"@dots{}"} literals to be laid out as constant CoreFoundation strings.
+Note that @option{-fconstant-cfstrings} is an alias for the target-specific
+@option{-mconstant-cfstrings} equivalent.
 
 @opindex fgnu-runtime
 @item -fgnu-runtime
@@ -24118,10 +24120,21 @@ This is by default ON@.
 @item -gfull
 Emit debugging information for all symbols and types.
 
+@opindex fconstant-cfstrings
+@item -fconstant-cfstrings
+The @option{-fconstant-cfstrings} is an alias for @option{-mconstant-cfstrings}.
+
+@opindex mconstant-cfstrings
+@item -mconstant-cfstrings
+When the NeXT runtime is being used (the default on these systems), override
+any @option{-fconstant-string-class} setting and cause @code{@@"@dots{}"}
+literals to be laid out as constant CoreFoundation strings.
+
+@opindex mmacosx-version-min
 @item -mmacosx-version-min=@var{version}
-The earliest version of MacOS X that this executable will run on
-is @var{version}.  Typical values of @var{version} include @code{10.1},
-@code{10.2}, and @code{10.3.9}.
+The earliest version of MacOS X that this executable will run on is
+@var{version}.  Typical values supported for @var{version} include @code{12},
+@code{10.12}, and @code{10.5.8}.
 
 If the compiler was built to use the system's headers by default,
 then the default for this option is the system version on which the