From 98d9cfabc19984d75951f7ee66037331da63c0b8 Mon Sep 17 00:00:00 2001
From: Marc Mutz <marc.mutz@qt.io>
Date: Wed, 21 Sep 2022 11:12:54 +0200
Subject: [PATCH] qCompress: return null, not empty, for OOM
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While this is a behavior change, we never documented that we'd return
an empty instead of a null QByteArray in this situation. Indeed,
returning bazip, with its fully-preserved capacity, is an expensive
way of signalling an error condition.

Conclude that this is not what the original author wanted and return a
default-constructed byte array instead, leaving bazip and its excess
capacity to be destroyed before the return from the function.

Pick-to: 6.4 6.3 6.2
Task-number: QTBUG-104972
Task-number: QTBUG-106542
Change-Id: I2ee1fc6fdbb9da28f1987b16915516b51bb348c3
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
---
 src/corelib/text/qbytearray.cpp | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/src/corelib/text/qbytearray.cpp b/src/corelib/text/qbytearray.cpp
index 6ae0237d55..fb55c630bf 100644
--- a/src/corelib/text/qbytearray.cpp
+++ b/src/corelib/text/qbytearray.cpp
@@ -606,9 +606,8 @@ QByteArray qCompress(const uchar* data, qsizetype nbytes, int compressionLevel)
             qToBigEndian(CompressSizeHint_t(nbytes), bazip.data());
             break;
         case Z_MEM_ERROR:
-            qWarning("qCompress: Z_MEM_ERROR: Not enough memory");
-            bazip.resize(0);
-            break;
+            return tooMuchData(ZLibOp::Compression);
+
         case Z_BUF_ERROR:
             len *= 2;
             break;