Refer to C23 in place of C2X in glibc

WG14 decided to use the name C23 as the informal name of the next
revision of the C standard (notwithstanding the publication date in
2024).  Update references to C2X in glibc to use the C23 name.

This is intended to update everything *except* where it involves
renaming files (the changes involving renaming tests are intended to
be done separately).  In the case of the _ISOC2X_SOURCE feature test
macro - the only user-visible interface involved - support for that
macro is kept for backwards compatibility, while adding
_ISOC23_SOURCE.

Tested for x86_64.

2 files changed, 12 insertions, 8 deletions

diff --git a/sysdeps/ieee754/ldbl-128ibm-compat/Makefile b/sysdeps/ieee754/ldbl-128ibm-compat/Makefile
index 34273a5f58..20cb2dbe35 100644
--- a/sysdeps/ieee754/ldbl-128ibm-compat/Makefile
+++ b/sysdeps/ieee754/ldbl-128ibm-compat/Makefile
@@ -354,8 +354,9 @@ tests += tst-ibm128-scanf-binary-c11 \
 	 tst-ieee128-scanf-binary-gnu11 \
 	 tst-ieee128-scanf-binary-gnu89
 
-# Some versions of GCC supported for building glibc do not support -std=c2x, so
-# the test for that version uses -std=c11 and then _ISOC2X_SOURCE is defined in
+# Some versions of GCC supported for building glibc do not support -std=c23
+# (added in GCC 14), or the older name -std=c2x (added in GCC 9), so
+# the test for that version uses -std=c11 and then _ISOC23_SOURCE is defined in
 # the test as needed.
 CFLAGS-tst-ibm128-scanf-binary-c11.c += -mabi=ibmlongdouble -Wno-psabi \
 					-std=c11 -DOBJPFX=\"$(objpfx)\"
@@ -390,8 +391,9 @@ tests += tst-ibm128-wscanf-binary-c11 \
 	 tst-ieee128-wscanf-binary-gnu11 \
 	 tst-ieee128-wscanf-binary-gnu89
 
-# Some versions of GCC supported for building glibc do not support -std=c2x, so
-# the test for that version uses -std=c11 and then _ISOC2X_SOURCE is defined in
+# Some versions of GCC supported for building glibc do not support -std=c23
+# (added in GCC 14), or the older name -std=c2x (added in GCC 9), so
+# the test for that version uses -std=c11 and then _ISOC23_SOURCE is defined in
 # the test as needed.
 CFLAGS-tst-ibm128-wscanf-binary-c11.c += -mabi=ibmlongdouble -Wno-psabi \
 					 -std=c11 -DOBJPFX=\"$(objpfx)\"
diff --git a/sysdeps/ieee754/ldbl-opt/Makefile b/sysdeps/ieee754/ldbl-opt/Makefile
index 0ed1cd2cae..f20c267081 100644
--- a/sysdeps/ieee754/ldbl-opt/Makefile
+++ b/sysdeps/ieee754/ldbl-opt/Makefile
@@ -236,8 +236,9 @@ tests += tst-nldbl-scanf-binary-c11 \
 	 tst-nldbl-scanf-binary-gnu11 \
 	 tst-nldbl-scanf-binary-gnu89
 
-# Some versions of GCC supported for building glibc do not support -std=c2x, so
-# the test for that version uses -std=c11 and then _ISOC2X_SOURCE is defined in
+# Some versions of GCC supported for building glibc do not support -std=c23
+# (added in GCC 14), or the older name -std=c2x (added in GCC 9), so
+# the test for that version uses -std=c11 and then _ISOC23_SOURCE is defined in
 # the test as needed.
 CFLAGS-tst-nldbl-scanf-binary-c11.c += -mlong-double-64 -std=c11 \
 				       -DOBJPFX=\"$(objpfx)\"
@@ -256,8 +257,9 @@ tests += tst-nldbl-wscanf-binary-c11 \
 	 tst-nldbl-wscanf-binary-gnu11 \
 	 tst-nldbl-wscanf-binary-gnu89
 
-# Some versions of GCC supported for building glibc do not support -std=c2x, so
-# the test for that version uses -std=c11 and then _ISOC2X_SOURCE is defined in
+# Some versions of GCC supported for building glibc do not support -std=c23
+# (added in GCC 14), or the older name -std=c2x (added in GCC 9), so
+# the test for that version uses -std=c11 and then _ISOC23_SOURCE is defined in
 # the test as needed.
 CFLAGS-tst-nldbl-wscanf-binary-c11.c += -mlong-double-64 -std=c11 \
 					-DOBJPFX=\"$(objpfx)\"