Revert "Refine {QString, QBA}::reallocData() logic"

This reverts commit 504972f838761f79a170c22225add496e7e5af6a.

Introduced realloc failures in qdoc.

Task-number: QTBUG-88258
Change-Id: I953e8d3933085022c75068af357ec9a44ab7e984
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

1 files changed, 5 insertions, 4 deletions

diff --git a/src/corelib/text/qbytearray.cpp b/src/corelib/text/qbytearray.cpp
index c482e2335e..f4ade684a0 100644
--- a/src/corelib/text/qbytearray.cpp
+++ b/src/corelib/text/qbytearray.cpp
@@ -1708,11 +1708,12 @@ void QByteArray::reallocData(qsizetype alloc, QArrayData::AllocationOption optio
         return;
     }
 
-    // don't use reallocate path when reducing capacity and there's free space
-    // at the beginning: might shift data pointer outside of allocated space
-    const bool cannotUseReallocate = d.freeSpaceAtBegin() > 0 && alloc < d.constAllocatedCapacity();
+    // there's a case of slow reallocate path where we need to memmove the data
+    // before a call to ::realloc(), meaning that there's an extra "heavy"
+    // operation. just prefer ::malloc() branch in this case
+    const bool slowReallocatePath = d.freeSpaceAtBegin() > 0;
 
-    if (d->needsDetach() || cannotUseReallocate) {
+    if (d->needsDetach() || slowReallocatePath) {
         DataPointer dd(Data::allocate(alloc, option), qMin(alloc, d.size));
         if (dd.size > 0)
             ::memcpy(dd.data(), d.data(), dd.size);