[src/trunk]: src/bin/sh PR bin/56972 Fix escape ('\') handling in sh read bu...

[kre <kre%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/0e9d0a69a397
branches:  trunk
changeset: 369462:0e9d0a69a397
user:      kre <kre%NetBSD.org@localhost>
date:      Fri Aug 19 12:17:18 2022 +0000

description:
PR bin/56972  Fix escape ('\') handling in sh read builtin.

In 1.35 (March 2005) (the big read fixup), most escape handling and IFS
processing in the read builtin was corrected.  However 2 cases were missed,
one is a word (something to be assigned to any variable but the last) in
which every character is escaped (the code was relying on a non-escaped char
to set the "in a word" status), and second trailing IFS whitespace at
the end of the line was being deleted, even if the chars had been escaped
(the escape chars are no longer present).

See the PR for more details (including the case that detected the problem).

After fixing this, I looked at the FreeBSD code (normally might do it
before, but these fixes were trivial) to check their implementation.
Their code does similar things to ours now does, but in a completely
different way, their read builtin is more complex than ours needs to
be (they handle more options).   For anyone tempted to simply incorporate
their code, note that it relies upon infrastructure changes elsewhere
in the shell, so would not be a simple cut and drop in exercise.

This needs pullups to -3 -4 -5 -6 -7 -8 and -9 (fortunately this is
happening before -10 is branched, so will never be broken this way there).

diffstat:

 bin/sh/miscbltin.c |  12 ++++++++----
 1 files changed, 8 insertions(+), 4 deletions(-)

diffs (64 lines):

diff -r c6048f6675af -r 0e9d0a69a397 bin/sh/miscbltin.c
--- a/bin/sh/miscbltin.c        Fri Aug 19 08:17:32 2022 +0000
+++ b/bin/sh/miscbltin.c        Fri Aug 19 12:17:18 2022 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: miscbltin.c,v 1.50 2022/04/16 14:26:26 kre Exp $       */
+/*     $NetBSD: miscbltin.c,v 1.51 2022/08/19 12:17:18 kre Exp $       */
 
 /*-
  * Copyright (c) 1991, 1993
@@ -37,7 +37,7 @@
 #if 0
 static char sccsid[] = "@(#)miscbltin.c        8.4 (Berkeley) 5/4/95";
 #else
-__RCSID("$NetBSD: miscbltin.c,v 1.50 2022/04/16 14:26:26 kre Exp $");
+__RCSID("$NetBSD: miscbltin.c,v 1.51 2022/08/19 12:17:18 kre Exp $");
 #endif
 #endif /* not lint */
 
@@ -100,6 +100,7 @@
        int i;
        int is_ifs;
        int saveall = 0;
+       ptrdiff_t wordlen = 0;
 
        rflag = 0;
        prompt = NULL;
@@ -137,7 +138,7 @@
                                break;
                        }
                        if (c != '\n')
-                               STPUTC(c, p);
+                               goto wdch;
                        continue;
                }
                if (c == '\n')
@@ -164,12 +165,14 @@
                }
 
                if (is_ifs == 0) {
+  wdch:;
                        /* append this character to the current variable */
                        startword = 0;
                        if (saveall)
                                /* Not just a spare terminator */
                                saveall++;
                        STPUTC(c, p);
+                       wordlen = p - stackblock();
                        continue;
                }
 
@@ -187,11 +190,12 @@
                setvar(*ap, stackblock(), 0);
                ap++;
                STARTSTACKSTR(p);
+               wordlen = 0;
        }
        STACKSTRNUL(p);
 
        /* Remove trailing IFS chars */
-       for (; stackblock() <= --p; *p = 0) {
+       for (; stackblock() + wordlen <= --p; *p = 0) {
                if (!strchr(ifs, *p))
                        break;
                if (strchr(" \t\n", *p))