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Date:      Wed, 13 Oct 2010 23:29:10 +0000 (UTC)
From:      "David E. O'Brien" <obrien@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r213814 - in head: bin/sh tools/regression/bin/sh/expansion
Message-ID:  <201010132329.o9DNTAGq004219@svn.freebsd.org>
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Author: obrien
Date: Wed Oct 13 23:29:09 2010
New Revision: 213814
URL: http://svn.freebsd.org/changeset/base/213814

Log:
  Do not assume in growstackstr() that a "precious" character will be
  immediately written into the stack after the call.  Instead let the caller
  manage the "space left".
  
  Previously, growstackstr()'s assumption causes problems with STACKSTRNUL()
  where we want to be able to turn a stack into a C string, and later
  pretend the NUL is not there.
  
  This fixes a bug in STACKSTRNUL() (that grew the stack) where:
  1. STADJUST() called after a STACKSTRNUL() results in an improper adjust.
     This can be seen in ${var%pattern} and ${var%%pattern} evaluation.
  2. Memory leak in STPUTC() called after a STACKSTRNUL().
  
  Reviewed by:	jilles

Added:
  head/tools/regression/bin/sh/expansion/trim4.0   (contents, props changed)
Modified:
  head/bin/sh/histedit.c
  head/bin/sh/memalloc.c
  head/bin/sh/memalloc.h

Modified: head/bin/sh/histedit.c
==============================================================================
--- head/bin/sh/histedit.c	Wed Oct 13 22:59:04 2010	(r213813)
+++ head/bin/sh/histedit.c	Wed Oct 13 23:29:09 2010	(r213814)
@@ -418,7 +418,7 @@ fc_replace(const char *s, char *p, char 
 		} else
 			STPUTC(*s++, dest);
 	}
-	STACKSTRNUL(dest);
+	STPUTC('\0', dest);
 	dest = grabstackstr(dest);
 
 	return (dest);

Modified: head/bin/sh/memalloc.c
==============================================================================
--- head/bin/sh/memalloc.c	Wed Oct 13 22:59:04 2010	(r213813)
+++ head/bin/sh/memalloc.c	Wed Oct 13 23:29:09 2010	(r213814)
@@ -295,6 +295,13 @@ grabstackblock(int len)
  * is space for at least one character.
  */
 
+static char *
+growstrstackblock(int n)
+{
+	growstackblock();
+	sstrnleft = stackblocksize() - n;
+	return stackblock() + n;
+}
 
 char *
 growstackstr(void)
@@ -304,12 +311,10 @@ growstackstr(void)
 	len = stackblocksize();
 	if (herefd >= 0 && len >= 1024) {
 		xwrite(herefd, stackblock(), len);
-		sstrnleft = len - 1;
+		sstrnleft = len;
 		return stackblock();
 	}
-	growstackblock();
-	sstrnleft = stackblocksize() - len - 1;
-	return stackblock() + len;
+	return growstrstackblock(len);
 }
 
 
@@ -323,9 +328,7 @@ makestrspace(void)
 	int len;
 
 	len = stackblocksize() - sstrnleft;
-	growstackblock();
-	sstrnleft = stackblocksize() - len;
-	return stackblock() + len;
+	return growstrstackblock(len);
 }
 
 

Modified: head/bin/sh/memalloc.h
==============================================================================
--- head/bin/sh/memalloc.h	Wed Oct 13 22:59:04 2010	(r213813)
+++ head/bin/sh/memalloc.h	Wed Oct 13 23:29:09 2010	(r213814)
@@ -67,9 +67,16 @@ void ungrabstackstr(char *, char *);
 #define stackblock() stacknxt
 #define stackblocksize() stacknleft
 #define STARTSTACKSTR(p)	p = stackblock(), sstrnleft = stackblocksize()
-#define STPUTC(c, p)	(--sstrnleft >= 0? (*p++ = (c)) : (p = growstackstr(), *p++ = (c)))
+#define STPUTC(c, p)	(--sstrnleft >= 0? (*p++ = (c)) : (p = growstackstr(), --sstrnleft, *p++ = (c)))
 #define CHECKSTRSPACE(n, p)	{ if (sstrnleft < n) p = makestrspace(); }
 #define USTPUTC(c, p)	(--sstrnleft, *p++ = (c))
+/*
+ * STACKSTRNUL's use is where we want to be able to turn a stack
+ * (non-sentinel, character counting string) into a C string,
+ * and later pretend the NUL is not there.
+ * Note: Because of STACKSTRNUL's semantics, STACKSTRNUL cannot be used
+ * on a stack that will grabstackstr()ed.
+ */
 #define STACKSTRNUL(p)	(sstrnleft == 0? (p = growstackstr(), *p = '\0') : (*p = '\0'))
 #define STUNPUTC(p)	(++sstrnleft, --p)
 #define STTOPC(p)	p[-1]

Added: head/tools/regression/bin/sh/expansion/trim4.0
==============================================================================
--- /dev/null	00:00:00 1970	(empty, because file is newly added)
+++ head/tools/regression/bin/sh/expansion/trim4.0	Wed Oct 13 23:29:09 2010	(r213814)
@@ -0,0 +1,15 @@
+# $FreeBSD$
+
+v1=/homes/SOME_USER
+v2=
+v3=C123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789
+
+# Trigger bug in VSTRIMRIGHT processing STADJUST() call in expand.c:subevalvar()
+while [ ${#v2} -lt 2000 ]; do
+	v4="${v2} ${v1%/*} $v3"
+	if [ ${#v4} -ne $((${#v2} + ${#v3} + 8)) ]; then
+		echo bad: ${#v4} -ne $((${#v2} + ${#v3} + 8))
+	fi
+	v2=x$v2
+	v3=y$v3
+done

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