From ca4eddea97c54a567c25e0fcf4641a6885f33bdf Mon Sep 17 00:00:00 2001
From: Minsoo Choo <minsoochoo0122@proton.me>
Date: Thu, 9 Jan 2025 11:13:06 -0500
Subject: [PATCH] src: Use gnu17 as the default C standard for userland instead
 of gnu99

Tracking newer versions of C (and C++) permits assuming newer language
features in the base system.  Some C11 extensions are already used in
the base system but implemented on top of GNU C extensions such as
_Alignas and _Static_assert.  In some cases the fallback versions in
cdefs.h are more limited than the native C11 extensions.

Even though C11 is the next major version of C, C17 is chosen instead
since C17 does not add new features to C but merely fixes defects in
C11.  It is also well supported by a wide range of clang (7.0.0+) and
GCC (8.1+) versions.

Along with changing the default, this change also removes explicit
requests for c11 via the CSTD variable in various Makefiles.

Libraries and binaries for ZFS continue to use c99.

PR:		284039 (exp-run)
Reviewed by:	imp, arichardson, emaste
Differential Revision:	https://reviews.freebsd.org/D43237
---
 libexec/tftpd/tests/Makefile | 1 -
 sbin/newfs_msdos/Makefile    | 1 -
 share/mk/bsd.sys.mk          | 3 +--
 usr.bin/sort/Makefile        | 1 -
 usr.bin/zstd/Makefile        | 1 -
 usr.sbin/makefs/Makefile     | 1 -
 6 files changed, 1 insertion(+), 7 deletions(-)

diff --git a/libexec/tftpd/tests/Makefile b/libexec/tftpd/tests/Makefile
index 661120335ac..d1faca03331 100644
--- a/libexec/tftpd/tests/Makefile
+++ b/libexec/tftpd/tests/Makefile
@@ -4,6 +4,5 @@ ATF_TESTS_C=	functional
 TEST_METADATA.functional+=	timeout=15
 
 LIBADD=	util
-CSTD=	c11
 
 .include <bsd.test.mk>
diff --git a/sbin/newfs_msdos/Makefile b/sbin/newfs_msdos/Makefile
index a3ea6a6a675..bd5b3486b6b 100644
--- a/sbin/newfs_msdos/Makefile
+++ b/sbin/newfs_msdos/Makefile
@@ -9,7 +9,6 @@ SRCS=	newfs_msdos.c mkfs_msdos.c
 .if ${MACHINE_CPUARCH} == "arm"
 WARNS?= 3
 .endif
-CSTD=	c11
 
 HAS_TESTS=
 SUBDIR.${MK_TESTS}+= tests
diff --git a/share/mk/bsd.sys.mk b/share/mk/bsd.sys.mk
index c136bf1e1af..63496e9b8cc 100644
--- a/share/mk/bsd.sys.mk
+++ b/share/mk/bsd.sys.mk
@@ -10,8 +10,7 @@
 
 .include <bsd.compiler.mk>
 
-# the default is gnu99 for now
-CSTD?=		gnu99
+CSTD?=		gnu17
 
 .if ${CSTD} == "c89" || ${CSTD} == "c90"
 CFLAGS+=	-std=iso9899:1990
diff --git a/usr.bin/sort/Makefile b/usr.bin/sort/Makefile
index 561af217af7..46cc431edd3 100644
--- a/usr.bin/sort/Makefile
+++ b/usr.bin/sort/Makefile
@@ -3,7 +3,6 @@
 PACKAGE= runtime
 PROG=	sort
 SRCS=	bwstring.c coll.c file.c mem.c radixsort.c sort.c vsort.c
-CSTD=	c11
 
 sort.1: sort.1.in
 	sed ${MAN_SUB} ${.ALLSRC} >${.TARGET}
diff --git a/usr.bin/zstd/Makefile b/usr.bin/zstd/Makefile
index dd54acbf83c..0e73e2eb0dd 100644
--- a/usr.bin/zstd/Makefile
+++ b/usr.bin/zstd/Makefile
@@ -25,7 +25,6 @@ MLINKS=	zstd.1 unzstd.1 \
 	zstd.1 zstdcat.1 \
 	zstd.1 zstdmt.1
 
-CSTD=c11
 WARNS?=	2
 LIBADD=	zstd
 .PATH: ${SRCTOP}/sys/contrib/zstd/programs
diff --git a/usr.sbin/makefs/Makefile b/usr.sbin/makefs/Makefile
index 75733714fcc..47a41cfac81 100644
--- a/usr.sbin/makefs/Makefile
+++ b/usr.sbin/makefs/Makefile
@@ -15,7 +15,6 @@ SRCS=	cd9660.c \
 MAN=	makefs.8
 
 NO_WCAST_ALIGN=
-CSTD=	c11
 
 .if ${MK_ZFS} != "no"
 SRCS+=	zfs.c