Transition to C99

NEWS

@@ -2,6 +2,10 @@ This documents significant changes in the dev branch of ksh 93u+m.
 For full details, see the git log at: https://github.com/ksh93/ksh
 Uppercase BUG_* IDs are shell bug IDs as used by the Modernish shell library.
 
+2026-04-15:
+
+- The ksh93 codebase now requires a C99 compiler to build.
+
 2026-04-14:
 
 - Ksh is now capable of allocating memory within a 64-bit address space. This

bin/package

@@ -125,7 +125,7 @@ command=${0##*/}
 case $(getopts '[-][123:xyz]' opt --xyz 2>/dev/null; echo 0$opt) in
 0123)	USAGE=$'
 [-?
-@(#)$Id: '$command$' (ksh 93u+m) 2026-04-02 $
+@(#)$Id: '$command$' (ksh 93u+m) 2026-04-15 $
 ]
 [-author?Glenn Fowler <gsf@research.att.com>]
 [-author?Contributors to https://github.com/ksh93/ksh]
@@ -559,7 +559,7 @@ SEE ALSO
   pkgadd(1), pkgmk(1), rpm(1), sh(1), tar(1), optget(3)
 
 IMPLEMENTATION
-  version         package (ksh 93u+m) 2026-04-02
+  version         package (ksh 93u+m) 2026-04-15
   author          Glenn Fowler <gsf@research.att.com>
   author          Contributors to https://github.com/ksh93/ksh
   copyright       (c) 1994-2012 AT&T Intellectual Property
@@ -2010,12 +2010,9 @@ case $x in
 			cd "$TMPDIR" || exit
 			cp $INITROOT/hello.c pkg$$.c || exit
 			trap "set +o noglob; rm -rf pkg$$.*" 0
-			if	! $cc -o pkg$$.exe pkg$$.c >pkg$$.e 2>&1
-			then	if	$cc -Dnew=old -o pkg$$.exe pkg$$.c >/dev/null 2>&1
-				then	err_out "$CC: must be a C compiler (not C++)"
-				fi
-				cat pkg$$.e
-				err_out "$CC: failed to compile and link $INITROOT/hello.c -- is it a C compiler?"
+			if	! $cc $CCFLAGS -o pkg$$.exe pkg$$.c >pkg$$.e 2>&1
+			then	cat pkg$$.e
+				err_out "$CC: failed to compile and link $INITROOT/hello.c -- is it a C99 compiler?"
 			fi
 			./pkg$$.exe >/dev/null 2>&1 || err_out \
 				"Cross-compiling is not supported. $CC seems to be a cross-compiler." \

src/cmd/INIT/README-mamake.md

@@ -4,7 +4,7 @@ MAM (Make Abstract Machine) is a simple rule-based make language
 that is implemented in just ten four-letter commands and four attributes,
 yet allows unlimited flexibility as it can execute arbitrary shell code.
 The program implementing MAM, `mamake`,
-is a portable C90 program written in a single file, `mamake.c`.
+is a portable C99 program written in a single file, `mamake.c`.
 This allows ksh 93u+m,
 or other programs using this build system,
 to be built using only a standard C compiler and utilities installation

src/cmd/INIT/hello.c

@@ -2,7 +2,7 @@
 *                                                                      *
 *               This software is part of the ast package               *
 *          Copyright (c) 1994-2011 AT&T Intellectual Property          *
-*          Copyright (c) 2020-2023 Contributors to ksh 93u+m           *
+*          Copyright (c) 2020-2026 Contributors to ksh 93u+m           *
 *                      and is licensed under the                       *
 *                 Eclipse Public License, Version 2.0                  *
 *                                                                      *
@@ -15,7 +15,31 @@
 *            Johnothan King <johnothanking@protonmail.com>             *
 *                                                                      *
 ***********************************************************************/
-#ifndef printf
-#include <stdio.h>
-#endif
-int main(void) { int new = 0; printf("hello world\n"); return new;}
+
+/*
+ * Compiler test used by bin/package to enforce C99 and block C++
+ */
+
+struct foo
+{
+	char *bar;
+	/* flexible array member requires C99 */
+	int baz[];
+};
+
+/* restrict requires C99, is an error in C++ */
+void r(const char *restrict cp)
+{
+	(void)cp;
+}
+
+int main(void)
+{
+	/* designated struct initializer requires C99 */
+	struct foo s = { .bar = "quux" };
+	/* variable name 'new' is an error in C++ */
+	int new = 0;
+
+	r(s.bar);
+	return new;
+}

src/cmd/INIT/iffe.sh

@@ -33,7 +33,7 @@ esac
 set -o noglob
 
 command=iffe
-version=2026-02-30
+version=2026-04-15
 
 # DEFPATH should be inherited from package(1)
 case $DEFPATH in
@@ -82,10 +82,10 @@ is_hdr() # [ - ] [ file.c ] hdr
 	esac
 	is hdr $1
 	case $1 in
-	sys/types.h | limits.h | stdio.h | unistd.h)
-		# These are often tested for repeatedly, especially sys/types.h.
-		# But POSIX has specified these since issue 1 (1988). It's 2023.
-		# Skip the compile to save time, but act like a positive test.
+	sys/types.h | limits.h | stddef.h | stdio.h | stdlib.h | unistd.h)
+		# These are often tested for repeatedly, but POSIX has specified
+		# these since issue 1 (1988). It's 2026. Skip the compile to save time,
+		# but act like a positive test.
 		: 2>$tmp.e
 		;;
 	*)	compile $cc -c $_is_hdr_file <&$nullin >&$nullout 2>$tmp.e
@@ -689,7 +689,7 @@ case $( (getopts '[-][123:xyz]' opt --xyz; echo 0$opt) 2>/dev/null ) in
 	}
 [+?\abegin\a\b{\b ... \b}end\b delimit multiline code blocks that override
 	or augment the default code provided by \biffe\b. User supplied code
-	blocks should be compatible with the C89/C90 C language
+	blocks should be compatible with the C99 C language
 	standard for maximal portability. Test code may call the function
 	\bNOTE("...")\b to emit short text in \b--verbose\b output; only one
 	\bNOTE()\b should be called per test for readability. In addition to
@@ -1162,7 +1162,6 @@ can=
 cansep=
 cctest=
 file=
-hdrtest=
 ifelse=NONE
 ifstack=
 ini=
@@ -2263,51 +2262,6 @@ int x;
 
 		cc="$cc $mac"
 
-		# check for global default headers (some cc -E insist on compiling)
-
-		case $hdrtest in
-		'')	hdrtest=1
-			allinc=
-			for x in types
-			do	case $config in
-				0)	c=_sys_${x}
-					;;
-				1)	case $shell in
-					ksh)	typeset -u u=$x ;;
-					*)	u=$(echo $x | tr abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ) ;;
-					esac
-					c=HAVE_SYS_${u}_H
-					;;
-				esac
-				x=sys/$x.h
-				echo "${allinc}#include <$x>" > $tmp.c
-				if	is_hdr $x
-				then	gothdr="$gothdr + $x"
-					case $explicit in
-					0)	can="$can$cansep#define $c	1	/* #include <$x> ok */"
-						nan="$nan$cansep$c=1"
-						cansep=$nl
-						;;
-					esac
-					eval $c=1
-					allinc="${allinc}#include <$x>$nl"
-				else	gothdr="$gothdr - $x"
-					case $explicit$all$config$undef in
-					0?1?|0??1)
-						can="$can$cansep#undef	$c		/* #include <$x> not ok */"
-						nan="$nan$cansep$c="
-						cansep=$nl
-						;;
-					01??)	can="$can$cansep#define $c	0	/* #include <$x> not ok */"
-						nan="$nan$cansep$c=0"
-						cansep=$nl
-						;;
-					esac
-				fi
-			done
-			;;
-		esac
-
 		# add implicit headers/libraries before the checks
 
 		case $op in