From 1aa76f11131f03e095b8df149e4f8ba406c88cde Mon Sep 17 00:00:00 2001
From: dkf <donal.k.fellows@manchester.ac.uk>
Date: Tue, 25 Apr 2017 19:32:46 +0000
Subject: [50750c735a] Fix for uninit memory handling issue in zlib transforms.

---
 generic/tclZlib.c | 34 ++++++++++++++++------------------
 tests/zlib.test   |  2 +-
 2 files changed, 17 insertions(+), 19 deletions(-)

diff --git a/generic/tclZlib.c b/generic/tclZlib.c
index 82486d2..fc20d7e 100644
--- a/generic/tclZlib.c
+++ b/generic/tclZlib.c
@@ -3113,30 +3113,28 @@ ZlibTransformOutput(
 		errorCodePtr);
     }
 
+    /*
+     * No zero-length writes. Flushes must be explicit.
+     */
+
+    if (toWrite == 0) {
+	return 0;
+    }
+
     cd->outStream.next_in = (Bytef *) buf;
     cd->outStream.avail_in = toWrite;
-    do {
+    while (cd->outStream.avail_in > 0) {
 	e = Deflate(&cd->outStream, cd->outBuffer, cd->outAllocated,
 		Z_NO_FLUSH, &produced);
+	if (e != Z_OK || produced == 0) {
+	    break;
+	}
 
-	if ((e == Z_OK && produced > 0) || e == Z_BUF_ERROR) {
-	    /*
-	     * deflate() indicates that it is out of space by returning
-	     * Z_BUF_ERROR *or* by simply returning Z_OK with no remaining
-	     * space; in either case, we must write the whole buffer out and
-	     * retry to compress what is left.
-	     */
-
-	    if (e == Z_BUF_ERROR) {
-		produced = cd->outAllocated;
-		e = Z_OK;
-	    }
-	    if (Tcl_WriteRaw(cd->parent, cd->outBuffer, produced) < 0) {
-		*errorCodePtr = Tcl_GetErrno();
-		return -1;
-	    }
+	if (Tcl_WriteRaw(cd->parent, cd->outBuffer, produced) < 0) {
+	    *errorCodePtr = Tcl_GetErrno();
+	    return -1;
 	}
-    } while (e == Z_OK && produced > 0 && cd->outStream.avail_in > 0);
+    }
 
     if (e == Z_OK) {
 	return toWrite - cd->outStream.avail_in;
diff --git a/tests/zlib.test b/tests/zlib.test
index 9f06eb1..c2f7825 100644
--- a/tests/zlib.test
+++ b/tests/zlib.test
@@ -1004,7 +1004,7 @@ test zlib-12.2 {Patrick Dunnigan's issue} -constraints zlib -setup {
 } -cleanup {
     removeFile $filesrc
     removeFile $filedst
-} -result 4152
+} -result 56
 
 ::tcltest::cleanupTests
 return
-- 
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