Fix undefined use of memcpy and memcmp

Don't call them on a nullptr, even with a length of 0.

Change-Id: I7fee23303562e5771697a16365cae12e3e87af6f
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

4 files changed, 17 insertions, 9 deletions

diff --git a/src/corelib/text/qbytearray.cpp b/src/corelib/text/qbytearray.cpp
index 5b1016e838..aee22edc6f 100644
--- a/src/corelib/text/qbytearray.cpp
+++ b/src/corelib/text/qbytearray.cpp
@@ -411,9 +411,11 @@ int qstrnicmp(const char *str1, qsizetype len1, const char *str2, qsizetype len2
  */
 int QtPrivate::compareMemory(QByteArrayView lhs, QByteArrayView rhs)
 {
-    int ret = memcmp(lhs.data(), rhs.data(), qMin(lhs.size(), rhs.size()));
-    if (ret != 0)
-        return ret;
+    if (!lhs.isNull() && !rhs.isNull()) {
+        int ret = memcmp(lhs.data(), rhs.data(), qMin(lhs.size(), rhs.size()));
+        if (ret != 0)
+            return ret;
+    }
 
     // they matched qMin(l1, l2) bytes
     // so the longer one is lexically after the shorter one
@@ -1638,7 +1640,8 @@ void QByteArray::reallocData(uint alloc, Data::ArrayOptions options)
 {
     if (d->needsDetach()) {
         DataPointer dd(Data::allocate(alloc, options), qMin(qsizetype(alloc) - 1, d.size));
-        ::memcpy(dd.data(), d.data(), dd.size);
+        if (dd.size > 0)
+            ::memcpy(dd.data(), d.data(), dd.size);
         dd.data()[dd.size] = 0;
         d = dd;
     } else {
diff --git a/src/corelib/text/qstring.cpp b/src/corelib/text/qstring.cpp
index 0334583900..b63b980e72 100644
--- a/src/corelib/text/qstring.cpp
+++ b/src/corelib/text/qstring.cpp
@@ -2364,7 +2364,8 @@ void QString::reallocData(size_t alloc, bool grow)
 
     if (d->needsDetach()) {
         DataPointer dd(Data::allocate(alloc, allocOptions), qMin(qsizetype(alloc) - 1, d.size));
-        ::memcpy(dd.data(), d.data(), dd.size * sizeof(QChar));
+        if (dd.size > 0)
+            ::memcpy(dd.data(), d.data(), dd.size * sizeof(QChar));
         dd.data()[dd.size] = 0;
         d = dd;
     } else {
diff --git a/src/corelib/text/qstringbuilder.h b/src/corelib/text/qstringbuilder.h
index 6ba01c0e30..512b7e7bf7 100644
--- a/src/corelib/text/qstringbuilder.h
+++ b/src/corelib/text/qstringbuilder.h
@@ -260,7 +260,8 @@ template <> struct QConcatenable<QString> : private QAbstractConcatenable
     static inline void appendTo(const QString &a, QChar *&out)
     {
         const int n = a.size();
-        memcpy(out, reinterpret_cast<const char*>(a.constData()), sizeof(QChar) * n);
+        if (n)
+            memcpy(out, reinterpret_cast<const char*>(a.constData()), sizeof(QChar) * n);
         out += n;
     }
 };
@@ -274,7 +275,8 @@ template <> struct QConcatenable<QStringRef> : private QAbstractConcatenable
     static inline void appendTo(const QStringRef &a, QChar *&out)
     {
         const int n = a.size();
-        memcpy(out, reinterpret_cast<const char*>(a.constData()), sizeof(QChar) * n);
+        if (n)
+            memcpy(out, reinterpret_cast<const char*>(a.constData()), sizeof(QChar) * n);
         out += n;
     }
 };
@@ -288,7 +290,8 @@ template <> struct QConcatenable<QStringView> : private QAbstractConcatenable
     static inline void appendTo(QStringView a, QChar *&out)
     {
         const auto n = a.size();
-        memcpy(out, a.data(), sizeof(QChar) * n);
+        if (n)
+            memcpy(out, a.data(), sizeof(QChar) * n);
         out += n;
     }
 };
diff --git a/src/corelib/tools/qhash.h b/src/corelib/tools/qhash.h
index eacc373ee3..2b1b155efb 100644
--- a/src/corelib/tools/qhash.h
+++ b/src/corelib/tools/qhash.h
@@ -397,7 +397,8 @@ struct Span {
         // we only add storage if the previous storage was fully filled, so
         // simply copy the old data over
         if constexpr (isRelocatable<Node>()) {
-            memcpy(newEntries, entries, allocated*sizeof(Entry));
+            if (allocated)
+                memcpy(newEntries, entries, allocated*sizeof(Entry));
         } else {
             for (size_t i = 0; i < allocated; ++i) {
                 new (&newEntries[i].node()) Node(std::move(entries[i].node()));