doc, c: Clarify status of decimal floating point support [PR123234]

At first glance, the GCC manual's section documenting decimal floating
point support as a C extension appears to be bit-rotten, since this
feature is now standardized in ISO C23.  In fact, though, GCC's
implementation is based on the older N1312 proposal, and full C23
support is not yet available.  This patch makes the GCC manual say that
explicitly.

gcc/ChangeLog
	PR c/123234
	* doc/extend.texi (Decimal Float): Clarify that GCC really does
	support only the older N1312 draft as documented here, not the
	standard C23 functionality yet.

diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index 47b0bdf13401ca5ead5247ed3e4cf163f1d0df97..b9d8b8955a9a7697cc9d966e6c4807292c2e0f81 100644 (file)
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -410,11 +410,12 @@ FPU.
 @cindex @code{DD} integer suffix
 @cindex @code{DL} integer suffix
 
-As an extension, GNU C supports decimal floating types as
-defined in the N1312 draft of ISO/IEC WDTR24732.  Support for decimal
-floating types in GCC will evolve as the draft technical report changes.
-Calling conventions for any target might also change.  Not all targets
-support decimal floating types.
+As an extension, GNU C supports decimal floating types as defined in
+the N1312 draft of ISO/IEC WDTR24732.  GCC does not yet implement the
+later specification of decimal floating point in the C23 standard,
+primarily due to problems with library support.  The N1312 draft
+support is available in all dialects of C, but not all targets support
+decimal floating types.
 
 The decimal floating types are @code{_Decimal32}, @code{_Decimal64}, and
 @code{_Decimal128}.  They use a radix of ten, unlike the floating types