Merge 10.4 into 10.5

3 files changed, 99 insertions, 29 deletions

diff --git a/include/my_atomic.h b/include/my_atomic.h
index 1c54c24d455..88f6746ba3d 100644
--- a/include/my_atomic.h
+++ b/include/my_atomic.h
@@ -2,6 +2,7 @@
 #define MY_ATOMIC_INCLUDED
 
 /* Copyright (c) 2006, 2010, Oracle and/or its affiliates. All rights reserved.
+   Copyright (c) 2018, 2020, MariaDB
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -169,4 +170,48 @@
   my_atomic_casptr((P), (E), (D))
 #endif
 
+#ifdef __cplusplus
+#include <atomic>
+/**
+  A wrapper for std::atomic, defaulting to std::memory_order_relaxed.
+
+  When it comes to atomic loads or stores at std::memory_order_relaxed
+  on IA-32 or AMD64, this wrapper is only introducing some constraints
+  to the C++ compiler, to prevent some optimizations of loads or
+  stores.
+
+  On POWER and ARM, atomic loads and stores involve different instructions
+  from normal loads and stores and will thus incur some overhead.
+
+  Because atomic read-modify-write operations will always incur
+  overhead, we intentionally do not define
+  operator++(), operator--(), operator+=(), operator-=(), or similar,
+  to make the overhead stand out in the users of this code.
+*/
+template <typename Type> class Atomic_relaxed
+{
+  std::atomic<Type> m;
+public:
+  Atomic_relaxed(const Atomic_relaxed<Type> &rhs)
+  { m.store(rhs, std::memory_order_relaxed); }
+  Atomic_relaxed(Type val) : m(val) {}
+  Atomic_relaxed() {}
+
+  operator Type() const { return m.load(std::memory_order_relaxed); }
+  Type operator=(const Type val)
+  { m.store(val, std::memory_order_relaxed); return val; }
+  Type operator=(const Atomic_relaxed<Type> &rhs) { return *this= Type{rhs}; }
+  Type fetch_add(const Type i, std::memory_order o= std::memory_order_relaxed)
+  { return m.fetch_add(i, o); }
+  Type fetch_sub(const Type i, std::memory_order o= std::memory_order_relaxed)
+  { return m.fetch_sub(i, o); }
+  bool compare_exchange_strong(Type& i1, const Type i2,
+                               std::memory_order o1= std::memory_order_relaxed,
+                               std::memory_order o2= std::memory_order_relaxed)
+  { return m.compare_exchange_strong(i1, i2, o1, o2); }
+  Type exchange(const Type i, std::memory_order o= std::memory_order_relaxed)
+  { return m.exchange(i, o); }
+};
+#endif /* __cplusplus */
+
 #endif /* MY_ATOMIC_INCLUDED */
diff --git a/include/my_valgrind.h b/include/my_valgrind.h
index 2c623a044f4..8aaa261fd5b 100644
--- a/include/my_valgrind.h
+++ b/include/my_valgrind.h
@@ -32,6 +32,7 @@
 
 #if defined(HAVE_VALGRIND_MEMCHECK_H) && defined(HAVE_valgrind)
 # include <valgrind/memcheck.h>
+# define HAVE_valgrind_or_MSAN
 # define MEM_UNDEFINED(a,len) VALGRIND_MAKE_MEM_UNDEFINED(a,len)
 # define MEM_MAKE_DEFINED(a,len) VALGRIND_MAKE_MEM_DEFINED(a,len)
 # define MEM_NOACCESS(a,len) VALGRIND_MAKE_MEM_NOACCESS(a,len)
@@ -50,6 +51,7 @@ https://github.com/google/sanitizers/wiki/AddressSanitizerManualPoisoning */
 # define REDZONE_SIZE 8
 #elif __has_feature(memory_sanitizer)
 # include <sanitizer/msan_interface.h>
+# define HAVE_valgrind_or_MSAN
 # define MEM_UNDEFINED(a,len) __msan_allocated_memory(a,len)
 # define MEM_MAKE_DEFINED(a,len) __msan_unpoison(a,len)
 # define MEM_NOACCESS(a,len) ((void) 0)
@@ -65,16 +67,19 @@ https://github.com/google/sanitizers/wiki/AddressSanitizerManualPoisoning */
 # define REDZONE_SIZE 0
 #endif /* HAVE_VALGRIND_MEMCHECK_H */
 
-#if defined(TRASH_FREED_MEMORY)
-/* NOTE: Do not invoke TRASH_FILL directly! Use TRASH_ALLOC or TRASH_FREE.
-
-The MEM_UNDEFINED() call before memset() is for canceling the effect
-of any previous MEM_NOACCESS(). We must invoke MEM_UNDEFINED() after
-writing the dummy pattern, unless MEM_NOACCESS() is going to be invoked.
-On AddressSanitizer, the MEM_UNDEFINED() in TRASH_ALLOC() has no effect. */
+#ifdef TRASH_FREED_MEMORY
+/*
+  TRASH_FILL() has to call MEM_UNDEFINED() to cancel any effect of TRASH_FREE().
+  This can happen in the case one does
+  TRASH_ALLOC(A,B) ; TRASH_FREE(A,B) ; TRASH_ALLOC(A,B)
+  to reuse the same memory in an internal memory allocator like MEM_ROOT.
+  For my_malloc() and safemalloc() the extra MEM_UNDEFINED is bit of an
+  overkill.
+  TRASH_FILL() is an internal function and should not be used externally.
+*/
 #define TRASH_FILL(A,B,C) do { const size_t trash_tmp= (B); MEM_UNDEFINED(A, trash_tmp); memset(A, C, trash_tmp); } while (0)
 #else
-#define TRASH_FILL(A,B,C) while (0)
+#define TRASH_FILL(A,B,C) do { MEM_UNDEFINED((A), (B)); } while (0)
 #endif
 /** Note that some memory became allocated or uninitialized. */
 #define TRASH_ALLOC(A,B) do { TRASH_FILL(A,B,0xA5); MEM_UNDEFINED(A,B); } while(0)
diff --git a/include/span.h b/include/span.h
index 0ed0158088c..0e8516933c6 100644
--- a/include/span.h
+++ b/include/span.h
@@ -24,11 +24,33 @@ this program; if not, write to the Free Software Foundation, Inc.,
 namespace st_
 {
 
+namespace detail
+{
+
+template <class T> struct remove_cv
+{
+  typedef T type;
+};
+template <class T> struct remove_cv<const T>
+{
+  typedef T type;
+};
+template <class T> struct remove_cv<volatile T>
+{
+  typedef T type;
+};
+template <class T> struct remove_cv<const volatile T>
+{
+  typedef T type;
+};
+
+} // namespace detail
+
 template <class ElementType> class span
 {
 public:
   typedef ElementType element_type;
-  typedef ElementType value_type;
+  typedef typename detail::remove_cv<ElementType>::type value_type;
   typedef size_t size_type;
   typedef ptrdiff_t difference_type;
   typedef element_type *pointer;
@@ -38,7 +60,6 @@ public:
   typedef pointer iterator;
   typedef const_pointer const_iterator;
   typedef std::reverse_iterator<iterator> reverse_iterator;
-  typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
 
   span() : data_(NULL), size_(0) {}
 
@@ -64,73 +85,72 @@ public:
 
   span &operator=(const span &other)
   {
-    data_= other.data_;
-    size_= other.size_;
+    data_= other.data();
+    size_= other.size();
     return *this;
   }
 
   template <size_t Count> span<element_type> first() const
   {
     assert(!empty());
-    return span(data_, 1);
+    return span(data(), 1);
   }
   template <size_t Count> span<element_type> last() const
   {
     assert(!empty());
-    return span(data_ + size() - 1, 1);
+    return span(data() + size() - 1, 1);
   }
 
   span<element_type> first(size_type count) const
   {
     assert(!empty());
-    return span(data_, 1);
+    return span(data(), 1);
   }
   span<element_type> last(size_type count) const
   {
     assert(!empty());
-    return span(data_ + size() - 1, 1);
+    return span(data() + size() - 1, 1);
   }
   span<element_type> subspan(size_type offset, size_type count) const
   {
     assert(!empty());
     assert(size() >= offset + count);
-    return span(data_ + offset, count);
+    return span(data() + offset, count);
   }
 
   size_type size() const { return size_; }
-  size_type size_bytes() const { return size_ * sizeof(ElementType); }
-  bool empty() const __attribute__((warn_unused_result)) { return size_ == 0; }
+  size_type size_bytes() const { return size() * sizeof(ElementType); }
+  bool empty() const __attribute__((warn_unused_result))
+  {
+    return size() == 0;
+  }
 
   reference operator[](size_type idx) const
   {
     assert(size() > idx);
-    return data_[idx];
+    return data()[idx];
   }
   reference front() const
   {
     assert(!empty());
-    return data_[0];
+    return data()[0];
   }
   reference back() const
   {
     assert(!empty());
-    return data_[size() - 1];
-  }
-  pointer data() const
-  {
-    assert(!empty());
-    return data_;
+    return data()[size() - 1];
   }
+  pointer data() const { return data_; }
 
   iterator begin() const { return data_; }
   iterator end() const { return data_ + size_; }
   reverse_iterator rbegin() const
   {
-    return std::reverse_iterator<iterator>(std::advance(end(), -1));
+    return std::reverse_iterator<iterator>(end());
   }
   reverse_iterator rend() const
   {
-    return std::reverse_iterator<iterator>(std::advance(begin(), -1));
+    return std::reverse_iterator<iterator>(begin());
   }
 
 private: