ksh/ksh93-backtick.dif

--- ./src/cmd/ksh93/sh/io.c.orig	2015-12-09 11:17:56.993309654 +0000
+++ ./src/cmd/ksh93/sh/io.c	2015-12-09 11:20:10.671805470 +0000
@@ -692,7 +692,7 @@ int sh_close(register int fd)
 	}
 	if(fd >= shp->gd->lim.open_max)
 		sh_iovalidfd(shp,fd);
-	if(!(sp=shp->sftable[fd]) || sfclose(sp) < 0)
+	if(!(sp=shp->sftable[fd]) || sffileno(sp) != fd || sfclose(sp) < 0)
 	{
 		int err=errno;
 		if(fdnotify)
--- ./src/cmd/ksh93/sh/jobs.c.orig	2015-11-27 12:18:44.168204649 +0000
+++ ./src/cmd/ksh93/sh/jobs.c	2015-11-27 14:49:54.255529119 +0000
@@ -1630,6 +1630,8 @@ int	job_wait(register pid_t pid)
 		}
 		sfsync(sfstderr);
 		job.waitsafe = 0;
+		if (pw && !job.savesig && shp->subshell)
+			sh_readpipedata();
 		nochild = job_reap(job.savesig);
 		if(job.waitsafe)
 			continue;
--- ./src/cmd/ksh93/sh/macro.c.orig	2015-08-11 12:00:52.454212675 +0000
+++ ./src/cmd/ksh93/sh/macro.c	2015-11-27 14:02:27.493074974 +0000
@@ -2183,7 +2183,7 @@ static void comsubst(Mac_t *mp,register
 		stkseek(stkp,soff+foff+64);
 		stkseek(stkp,soff);
 	}
-	if(foff > IOBSIZE)
+	if(sffileno(sp)>=0 && foff>(Sfoff_t)IOBSIZE)
 		sfsetbuf(sp,NULL,SF_UNBOUND);
 	while((str=(char*)sfreserve(sp,SF_UNBOUND,0)) && (c=bufsize=sfvalue(sp))>0)
 	{
--- ./src/cmd/ksh93/sh/subshell.c.orig	2015-08-11 11:59:29.030528394 +0000
+++ ./src/cmd/ksh93/sh/subshell.c	2015-12-09 11:20:38.614700038 +0000
@@ -105,11 +105,23 @@ static struct subshell
 #if SHOPT_COSHELL
 	void		*coshell;
 #endif /* SHOPT_COSHELL */
+	char		*pipedata;
+	size_t		pipedatalen;
 } *subshell_data;
 
 static long subenv;
 
 
+static void sh_addtopipedata(struct subshell *sp, void *buf, size_t len) 
+{
+        if (!sp->pipedata)
+                sp->pipedata = malloc(len);
+        else
+                sp->pipedata = realloc(sp->pipedata, sp->pipedatalen + len);
+        memcpy(sp->pipedata + sp->pipedatalen, buf, len);
+        sp->pipedatalen += len; 
+}
+
 /*
  * This routine will turn the sftmp() file into a real /tmp file or pipe
  * if the /tmp file create fails
@@ -146,7 +158,7 @@ void	sh_subtmpfile(Shell_t *shp)
 			sh_fcntl(sp->pipefd,F_SETFD,FD_CLOEXEC);
 			/* write the data to the pipe */
 			if(off = sftell(sfstdout))
-				write(fds[1],sfsetbuf(sfstdout,(Void_t*)sfstdout,0),(size_t)off);
+				sh_addtopipedata(sp, sfsetbuf(sfstdout,(Void_t*)sfstdout,0),(size_t)off);
 			sfclose(sfstdout);
 			if((sh_fcntl(fds[1],F_DUPFD, 1)) != 1)
 				errormsg(SH_DICT,ERROR_system(1),e_file+4);
@@ -173,6 +185,50 @@ void	sh_subtmpfile(Shell_t *shp)
 	}
 }
 
+void sh_readpipedata()
+{
+	register struct subshell *sp = subshell_data;
+	fd_set rfd;
+	if (sp)
+		sp = sp->pipe;
+	if (!sp || sp->pipefd < 0 || sp->pipefd >= FD_SETSIZE)
+		return;
+	sigset_t sigsaved, sigchld;
+	sigemptyset(&sigchld);
+	sigaddset(&sigchld, SIGCHLD);
+	/* block sigchild */
+	sigprocmask(SIG_BLOCK, &sigchld, &sigsaved);
+	FD_ZERO(&rfd);
+	FD_SET(sp->pipefd, &rfd);
+	while (!job.savesig) {
+		int i = pselect(sp->pipefd + 1, &rfd, 0, 0, 0, &sigsaved);
+		if (i > 0) {
+			char buf[4096];
+			i = read(sp->pipefd, buf, 4096);
+			if (i == 0 || (i < 0 && errno != EINTR))
+				break;
+			sh_addtopipedata(sp, buf, i);
+		}
+	}
+	sigprocmask(SIG_SETMASK, &sigsaved, 0);
+}
+
+void sh_emptypipe(struct subshell *sp, int pipefd)
+{
+	int i;
+	char buf[4096];
+	if (!sp || pipefd < 0)
+		return;
+	for (;;) {
+		i = read(pipefd, buf, 4096);
+		if (i < 0 && errno == EINTR)
+			continue;
+		if (i <= 0)
+			break;
+		sh_addtopipedata(sp, buf, i);
+	}
+}
+
 
 /*
  * This routine creates a temp file if necessary and creates a subshell.
@@ -614,7 +670,7 @@ Sfio_t *sh_subshell(Shell_t *shp,Shnode_
 			sp->tmpfd = -1;
 			sp->pipefd = -1;
 			/* use sftmp() file for standard output */
-			if(!(iop = sftmp(comsub==1?PIPE_BUF:IOBSIZE)))
+			if(!(iop = sftmp(comsub==1?SF_UNBOUND:IOBSIZE)))
 			{
 				sfswap(sp->saveout,sfstdout);
 				errormsg(SH_DICT,ERROR_system(1),e_tmpcreate);
@@ -822,6 +878,22 @@ Sfio_t *sh_subshell(Shell_t *shp,Shnode_
 		sh_argfree(shp,argsav,0);
 	if(shp->topfd != buff.topfd)
 		sh_iorestore(shp,buff.topfd|IOSUBSHELL,jmpval);
+
+	/* empty the pipe and move all data into iop */
+	if (comsub && sp->pipefd>=0)
+	{
+		sh_emptypipe(sp, sffileno(iop));
+		sfclose(iop);
+		sp->pipefd = -1;
+		iop = sftmp(SF_UNBOUND);
+		if (sp->pipedatalen)
+			sfwrite(iop, sp->pipedata, sp->pipedatalen);
+		if (sp->pipedata)
+			free(sp->pipedata);
+		sp->pipedata = 0;
+		sp->pipedatalen = 0;
+	}
+
 	if(sp->sig)
 	{
 		if(sp->prev)