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Subjectpatch for "bizarre read bug" in klibc dash
I had forked ash awhile back, patched up a few things to behave the
way I wanted them.
While I was at it, I fixed the "echo X | read X ; echo $X" bug that
echoed a blank line.
I tried awhile ago to raise who was responsible for the code and got nowhere.

I suppose you think the above code is a bizarre corner case. It is
not. I use very
complex shell expressions (think loops and subshells) in pipes, with
read in the end to
get the variable I was looking for. The work-around is particularly ugly.

I was quite surprised that this bug never got squashed in dash. So, I
backported it.

Well, here's the patch.

--- usr/dash/eval.c.orig 2006-06-14 19:48:47.000000000 -0700
+++ usr/dash/eval.c 2006-06-14 20:07:58.000000000 -0700
@@ -539,7 +539,17 @@
sh_error("Pipe call failed");
}
}
- if (forkshell(jp, lp->n, n->npipe.backgnd) == 0) {
+ if (!lp->next) {
+ extern void tempredir0(int prevfd);
+ /* Fix for "bizarre read bug" */
+ if (prevfd > 0) {
+ tempredir0(prevfd);
+ close(prevfd);
+ }
+ evaltree(lp->n, 0);
+ if (prevfd > 0)
+ popredir(0);
+ } else if (forkshell(jp, lp->n, n->npipe.backgnd) == 0) {
INTON;
if (pip[1] >= 0) {
close(pip[0]);
--- usr/dash/redir.c.orig 2006-06-14 19:59:21.000000000 -0700
+++ usr/dash/redir.c 2006-06-14 20:03:38.000000000 -0700
@@ -310,6 +310,21 @@
}


+void tempredir0(int fd)
+{
+ struct redirtab *sv = redirlist;
+ int i;
+ sv = ckmalloc(sizeof (struct redirtab));
+ for (i = 0 ; i < 10 ; i++)
+ sv->renamed[i] = EMPTY;
+ sv->next = redirlist;
+ redirlist = sv;
+ INTOFF;
+ sv->renamed[0] = copyfd(0, 10);
+ close(0);
+ copyfd(fd, 0);
+ INTON;
+}

/*
* Undo the effects of the last redirection.
-
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