From 1a61b85a2c04d48496a2e83359bf1d65abbc14dc Mon Sep 17 00:00:00 2001
From: Marc Mutz <marc.mutz@qt.io>
Date: Tue, 30 Nov 2021 15:45:50 +0100
Subject: [PATCH] QVarLengthArray: simplify default ctor
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Instead of calling the QVLA(qsizetype) ctor and letting the optimizer
and inliner have a field day on them, simply set the trivial values
for a, s, and ptr manually.

Mark it as noexcept.

Task-number: QTBUG-84785
Change-Id: I011826eacdaf63a4c37b21465e5fe4a6e70a1ab7
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
---
 src/corelib/tools/qvarlengtharray.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/corelib/tools/qvarlengtharray.h b/src/corelib/tools/qvarlengtharray.h
index 3668ebcfc9..18066a80ef 100644
--- a/src/corelib/tools/qvarlengtharray.h
+++ b/src/corelib/tools/qvarlengtharray.h
@@ -63,7 +63,10 @@ class QVarLengthArray
     static_assert(std::is_nothrow_destructible_v<T>, "Types with throwing destructors are not supported in Qt containers.");
 
 public:
-    QVarLengthArray() : QVarLengthArray(0) {}
+    QVarLengthArray() noexcept
+        : a{Prealloc}, s{0}, ptr{reinterpret_cast<T *>(array)}
+    {
+    }
 
     inline explicit QVarLengthArray(qsizetype size);