diff options
| -rw-r--r-- | core/fxcrt/cfx_unowned_ptr.h | 34 |
1 files changed, 29 insertions, 5 deletions
diff --git a/core/fxcrt/cfx_unowned_ptr.h b/core/fxcrt/cfx_unowned_ptr.h index da1875c7ab..5376781d6a 100644 --- a/core/fxcrt/cfx_unowned_ptr.h +++ b/core/fxcrt/cfx_unowned_ptr.h @@ -10,6 +10,30 @@ #include <type_traits> #include <utility> +// CFX_UnownedPtr is a smart pointer class that behaves very much like a +// standard C-style pointer. The advantages of using it over raw +// pointers are: +// +// 1. It documents the nature of the pointer with no need to add a comment +// explaining that is it // Not owned. Additionally, an attempt to delete +// an unowned ptr will fail to compile rather than silently succeeding, +// since it is a class and not a raw pointer. +// +// 2. When built for a memory tool like ASAN, the class provides a destructor +// which checks that the object being pointed to is still alive. +// +// Hence, when using UnownedPtr, no dangling pointers are ever permitted, +// even if they are not de-referenced after becoming dangling. The style of +// programming required is that the lifetime an object containing an +// UnownedPtr must be strictly less than the object to which it points. +// +// The same checks are also performed at assignment time to prove that the +// old value was not a dangling pointer, either. +// +// The array indexing operation [] is not supported on an unowned ptr, +// because an unowned ptr expresses a one to one relationship with some +// other heap object. + template <class T> class CFX_UnownedPtr { public: @@ -23,16 +47,16 @@ class CFX_UnownedPtr { // NOLINTNEXTLINE(runtime/explicit) CFX_UnownedPtr(std::nullptr_t ptr) {} - ~CFX_UnownedPtr() { Probe(); } + ~CFX_UnownedPtr() { ProbeForLowSeverityLifetimeIssue(); } CFX_UnownedPtr& operator=(T* that) { - Probe(); + ProbeForLowSeverityLifetimeIssue(); m_pObj = that; return *this; } CFX_UnownedPtr& operator=(const CFX_UnownedPtr& that) { - Probe(); + ProbeForLowSeverityLifetimeIssue(); if (*this != that) m_pObj = that.Get(); return *this; @@ -59,7 +83,7 @@ class CFX_UnownedPtr { T* Get() const { return m_pObj; } T* Release() { - Probe(); + ProbeForLowSeverityLifetimeIssue(); T* pTemp = nullptr; std::swap(pTemp, m_pObj); return pTemp; @@ -70,7 +94,7 @@ class CFX_UnownedPtr { T* operator->() const { return m_pObj; } private: - inline void Probe() { + inline void ProbeForLowSeverityLifetimeIssue() { #if defined(MEMORY_TOOL_REPLACES_ALLOCATOR) if (m_pObj) reinterpret_cast<const volatile uint8_t*>(m_pObj)[0]; |