• implement fcntl(2)-based advisory locking as an alternative iff flock(2)

is not found, from a suggestion by RT (LP: #912691)
• try harder (in a loop) to acquire a file lock if the locking mechanism
  documents EINTR is a possibility (fcntl always, flock on Linux not .Ox)
• use -std=c99 not -std=gnu99 if it must be at all

Build.sh

@@ -1,5 +1,5 @@
 #!/bin/sh
-srcversion='$MirOS: src/bin/mksh/Build.sh,v 1.517 2012/03/27 21:23:50 tg Exp $'
+srcversion='$MirOS: src/bin/mksh/Build.sh,v 1.518 2012/03/27 22:36:48 tg Exp $'
 #-
 # Copyright (c) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010,
 #		2011, 2012
@@ -1335,7 +1335,7 @@ else
 		#define EXTERN
 		#define MKSH_INCLUDES_ONLY
 		#include "sh.h"
-		__RCSID("$MirOS: src/bin/mksh/Build.sh,v 1.517 2012/03/27 21:23:50 tg Exp $");
+		__RCSID("$MirOS: src/bin/mksh/Build.sh,v 1.518 2012/03/27 22:36:48 tg Exp $");
 		int main(void) { printf("Hello, World!\n"); return (0); }
 EOF
 	case $cm in
@@ -1399,19 +1399,18 @@ EOF
 #
 # Environment: library functions
 #
-ac_testn flock_ex '' 'flock and mmap' <<-'EOF'
+ac_test flock <<-'EOF'
-	#include <sys/types.h>
-	#if HAVE_SYS_FILE_H
-	#include <sys/file.h>
-	#endif
-	#if HAVE_SYS_MMAN_H
-	#include <sys/mman.h>
-	#endif
 	#include <fcntl.h>
-	#include <stdlib.h>
+	int main(void) { return (flock(0, LOCK_EX | LOCK_UN)); }
-	int main(void) { return ((void *)mmap(NULL, (size_t)flock(0, LOCK_EX),
+EOF
-	    PROT_READ, MAP_PRIVATE, 0, (off_t)0) == (void *)NULL ? 1 :
+
-	    munmap(NULL, 0)); }
+ac_test lock_fcntl '!' flock 1 'whether we can lock files with fcntl' <<-'EOF'
+	#include <fcntl.h>
+	int main(void) {
+		struct flock lks;
+		lks.l_type = F_WRLCK | F_UNLCK;
+		return (fcntl(0, F_SETLKW, &lks));
+	}
 EOF
 
 ac_test getrusage <<-'EOF'
@@ -1446,6 +1445,20 @@ ac_test mkstemp <<-'EOF'
 	int main(void) { char tmpl[] = "X"; return (mkstemp(tmpl)); }
 EOF
 
+ac_test mmap lock_fcntl 0 'for mmap and munmap' <<-'EOF'
+	#include <sys/types.h>
+	#if HAVE_SYS_FILE_H
+	#include <sys/file.h>
+	#endif
+	#if HAVE_SYS_MMAN_H
+	#include <sys/mman.h>
+	#endif
+	#include <stdlib.h>
+	int main(void) { return ((void *)mmap(NULL, (size_t)0,
+	    PROT_READ, MAP_PRIVATE, 0, (off_t)0) == (void *)NULL ? 1 :
+	    munmap(NULL, 0)); }
+EOF
+
 ac_test nice <<-'EOF'
 	#include <unistd.h>
 	int main(void) { return (nice(4)); }
@@ -1536,7 +1549,7 @@ EOF
 #
 save_CC=$CC; save_LDFLAGS=$LDFLAGS; save_LIBS=$LIBS
 CC="$CC -c -o $tcfn"; LDFLAGS=; LIBS=
-ac_test '!' flock_decl flock_ex 1 'if flock() does not need to be declared' <<-'EOF'
+ac_test '!' flock_decl flock 1 'if flock() does not need to be declared' <<-'EOF'
 	#define MKSH_INCLUDES_ONLY
 	#include "sh.h"
 	long flock(void);		/* this clashes if defined before */
@@ -1559,7 +1572,9 @@ CC=$save_CC; LDFLAGS=$save_LDFLAGS; LIBS=$save_LIBS
 # other checks
 #
 fd='if to use persistent history'
-ac_cache PERSISTENT_HISTORY || test 0 = $HAVE_FLOCK_EX || fv=1
+ac_cache PERSISTENT_HISTORY || case $HAVE_MMAP$HAVE_FLOCK$HAVE_LOCL_FCNTL in
+11*|101) fv=1 ;;
+esac
 test 1 = $fv || check_categories="$check_categories no-histfile"
 ac_testdone
 ac_cppflags

Makefile

@@ -1,6 +1,7 @@
-# $MirOS: src/bin/mksh/Makefile,v 1.94 2012/03/27 21:23:51 tg Exp $
+# $MirOS: src/bin/mksh/Makefile,v 1.95 2012/03/27 22:36:49 tg Exp $
 #-
-# Copyright (c) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011
+# Copyright (c) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010,
+#		2011, 2012
 #	Thorsten Glaser <tg@mirbsd.org>
 #
 # Provided that these terms and disclaimer and all copyright notices
@@ -39,7 +40,8 @@ CPPFLAGS+=	-DMKSH_ASSUME_UTF8 -DMKSH_DISABLE_DEPRECATED \
 		-DHAVE_CAN_INTTYPES=1 -DHAVE_CAN_UCBINTS=1 \
 		-DHAVE_CAN_INT8TYPE=1 -DHAVE_CAN_UCBINT8=1 -DHAVE_RLIM_T=1 \
 		-DHAVE_SIG_T=1 -DHAVE_SYS_SIGNAME=1 -DHAVE_SYS_SIGLIST=1 \
-		-DHAVE_STRSIGNAL=0 -DHAVE_GETRUSAGE=1 -DHAVE_KILLPG=1 \
+		-DHAVE_STRSIGNAL=0 -DHAVE_FLOCK=1 -DHAVE_LOCK_FCNTL=1 \
+		-DHAVE_MMAP=1 -DHAVE_GETRUSAGE=1 -DHAVE_KILLPG=1 \
 		-DHAVE_MKNOD=0 -DHAVE_MKSTEMP=1 -DHAVE_NICE=1 -DHAVE_REVOKE=1 \
 		-DHAVE_SETLOCALE_CTYPE=0 -DHAVE_LANGINFO_CODESET=0 \
 		-DHAVE_SELECT=1 -DHAVE_SETRESUGID=1 -DHAVE_SETGROUPS=1 \
@@ -49,7 +51,7 @@ CPPFLAGS+=	-DMKSH_ASSUME_UTF8 -DMKSH_DISABLE_DEPRECATED \
 # probably differs between i386 and sparc
 CPPFLAGS+=	-DHAVE_SILENT_IDIVWRAPV=0
 CPPFLAGS+=	-D${${PROG:L}_tf:C/(Mir${MAN:E}{0,1}){2}/4/:S/x/mksh_BUILD/:U}
-COPTS+=		-std=gnu99 -Wall
+COPTS+=		-std=c99 -Wall
 .endif
 
 USE_PRINTF_BUILTIN?=	0

check.t

@@ -1,4 +1,4 @@
-# $MirOS: src/bin/mksh/check.t,v 1.523 2012/03/26 21:10:38 tg Exp $
+# $MirOS: src/bin/mksh/check.t,v 1.524 2012/03/27 22:36:49 tg Exp $
 # $OpenBSD: bksl-nl.t,v 1.2 2001/01/28 23:04:56 niklas Exp $
 # $OpenBSD: history.t,v 1.5 2001/01/28 23:04:56 niklas Exp $
 # $OpenBSD: read.t,v 1.3 2003/03/10 03:48:16 david Exp $
@@ -29,7 +29,7 @@
 # http://www.freebsd.org/cgi/cvsweb.cgi/src/tools/regression/bin/test/regress.sh?rev=HEAD
 
 expected-stdout:
-	@(#)MIRBSD KSH R40 2012/03/26
+	@(#)MIRBSD KSH R40 2012/03/27
 description:
 	Check version of shell.
 stdin:

histrap.c

@@ -2,7 +2,8 @@
 /*	$OpenBSD: trap.c,v 1.23 2010/05/19 17:36:08 jasper Exp $	*/
 
 /*-
- * Copyright (c) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011
+ * Copyright (c) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010,
+ *		 2011, 2012
  *	Thorsten Glaser <tg@mirbsd.org>
  *
  * Provided that these terms and disclaimer and all copyright notices
@@ -26,7 +27,7 @@
 #include <sys/file.h>
 #endif
 
-__RCSID("$MirOS: src/bin/mksh/histrap.c,v 1.117 2011/12/31 00:47:45 tg Exp $");
+__RCSID("$MirOS: src/bin/mksh/histrap.c,v 1.118 2012/03/27 22:36:52 tg Exp $");
 
 Trap sigtraps[NSIG + 1];
 static struct sigaction Sigact_ign;
@@ -723,7 +724,7 @@ hist_init(Source *s)
 	if (histfd != fd)
 		close(fd);
 
-	(void)flock(histfd, LOCK_EX);
+	mksh_lockfd(histfd);
 
 	histfsize = lseek(histfd, (off_t)0, SEEK_END);
 	if (histfsize > MKSH_MAXHISTFSIZE || hs == hist_init_restore) {
@@ -815,7 +816,7 @@ hist_init(Source *s)
 	}
 	histfsize = lseek(histfd, (off_t)0, SEEK_END);
  hist_init_tail:
-	(void)flock(histfd, LOCK_UN);
+	mksh_unlkfd(histfd);
 #endif
 }
 
@@ -880,7 +881,7 @@ writehistfile(int lno, const char *cmd)
 	size_t bytes;
 	unsigned char *base, *news;
 
-	(void)flock(histfd, LOCK_EX);
+	mksh_lockfd(histfd);
 	sizenow = lseek(histfd, (off_t)0, SEEK_END);
 	if (sizenow < histfsize) {
 		/* the file has shrunk; give up */
@@ -917,7 +918,7 @@ writehistfile(int lno, const char *cmd)
 		return;
 	}
 	histfsize = lseek(histfd, (off_t)0, SEEK_END);
-	(void)flock(histfd, LOCK_UN);
+	mksh_unlkfd(histfd);
 }
 
 static int
@@ -938,7 +939,7 @@ writehistline(int fd, int lno, const char *cmd)
 void
 hist_finish(void)
 {
-	(void)flock(histfd, LOCK_UN);
+	mksh_unlkfd(histfd);
 	(void)close(histfd);
 	histfd = -1;
 }
@@ -1419,3 +1420,53 @@ setexecsig(Trap *p, int restore)
 		break;
 	}
 }
+
+#if HAVE_PERSISTENT_HISTORY || defined(DF)
+/*
+ * File descriptor locking and unlocking functions.
+ * Could use some error handling, but hey, this is only
+ * advisory locking anyway, will often not work over NFS,
+ * and you are SOL if this fails...
+ */
+
+void
+mksh_lockfd(int fd)
+{
+#if defined(__OpenBSD__)
+	/* flock is not interrupted by signals */
+	(void)flock(fd, LOCK_EX);
+#elif HAVE_FLOCK
+	int rv;
+
+	/* e.g. on Linux */
+	do {
+		rv = flock(fd, LOCK_EX);
+	} while (rv == 1 && errno == EINTR);
+#elif HAVE_LOCK_FCNTL
+	int rv;
+	struct flock lks;
+
+	memset(&lks, 0, sizeof(lks));
+	lks.l_type = F_WRLCK;
+	do {
+		rv = fcntl(fd, F_SETLKW, &lks);
+	} while (rv == 1 && errno == EINTR);
+#else
+#error oops
+#endif
+}
+
+void
+mksh_unlkfd(int fd)
+{
+#if HAVE_FLOCK
+	(void)flock(fd, LOCK_UN);
+#elif HAVE_LOCK_FCNTL
+	struct flock lks;
+
+	memset(&lks, 0, sizeof(lks));
+	lks.l_type = F_UNLCK;
+	(void)fcntl(fd, F_SETLKW, &lks);
+#endif
+}
+#endif

main.c

@@ -34,7 +34,7 @@
 #include <locale.h>
 #endif
 
-__RCSID("$MirOS: src/bin/mksh/main.c,v 1.211 2012/03/25 14:28:14 tg Exp $");
+__RCSID("$MirOS: src/bin/mksh/main.c,v 1.212 2012/03/27 22:36:52 tg Exp $");
 
 extern char **environ;
 
@@ -1721,7 +1721,7 @@ DF(const char *fmt, ...)
 	va_list args;
 	struct timeval tv;
 
-	(void)flock(shl_dbg_fd, LOCK_EX);
+	mksh_lockfd(shl_dbg_fd);
 	gettimeofday(&tv, NULL);
 	shf_fprintf(shl_dbg, "[%d.%06d:%d] ", (int)tv.tv_sec, (int)tv.tv_usec,
 	    (int)getpid());
@@ -1730,6 +1730,6 @@ DF(const char *fmt, ...)
 	va_end(args);
 	shf_putc('\n', shl_dbg);
 	shf_flush(shl_dbg);
-	(void)flock(shl_dbg_fd, LOCK_UN);
+	mksh_unlkfd(shl_dbg_fd);
 }
 #endif

sh.h

@@ -152,9 +152,9 @@
 #endif
 
 #ifdef EXTERN
-__RCSID("$MirOS: src/bin/mksh/sh.h,v 1.530 2012/03/27 21:23:52 tg Exp $");
+__RCSID("$MirOS: src/bin/mksh/sh.h,v 1.531 2012/03/27 22:36:53 tg Exp $");
 #endif
-#define MKSH_VERSION "R40 2012/03/26"
+#define MKSH_VERSION "R40 2012/03/27"
 
 /* arithmetic types: C implementation */
 #if !HAVE_CAN_INTTYPES
@@ -1663,6 +1663,10 @@ int block_pipe(void);
 void restore_pipe(int);
 int setsig(Trap *, sig_t, int);
 void setexecsig(Trap *, int);
+#if HAVE_FLOCK || HAVE_LOCK_FCNTL
+void mksh_lockfd(int);
+void mksh_unlkfd(int);
+#endif
 /* jobs.c */
 void j_init(void);
 void j_exit(void);