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Merge pull request MicrosoftDocs#3120 from hwisungi/master
VC Code Analysis - adding help docs for new rules added in 16.8
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‎docs/code-quality/c33001.md

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---
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title: c33001
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description: C33001 warning for VARIANTs
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keywords: c33001
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author: hwisungi
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ms.author: hwisungi
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ms.date: 06/20/2020
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ms.topic: reference
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f1_keywords: ["C33001"]
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helpviewer_keywords: ["C33001"]
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dev_langs: ["C++"]
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---
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# C33001
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> Warning C33001: VARIANT 'var' was cleared when it was uninitialized (expression 'expr')
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This warning is triggered when an uninitialized VARIANT is passed into an API such as VariantClear
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that expects an initialized VARIANT.
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## Example
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```cpp
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#include <Windows.h>
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HRESULT foo(bool some_condition)
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{
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VARIANT var;
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if (some_condition)
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{
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//...
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VariantInit(&var);
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//...
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}
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VariantClear(&var); // C33001
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}
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```
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These warnings are corrected by ensuring VariantClear is called only for a properly initialized VARIANT:
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```cpp
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#include <Windows.h>
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HRESULT foo(bool some_condition)
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{
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VARIANT var;
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if (some_condition)
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{
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//...
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VariantInit(&var);
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//...
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VariantClear(&var); // C33001
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}
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}
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```
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## See also
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[C33004](/cpp/code-quality/c33004)
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[C33005](/cpp/code-quality/c33005)

‎docs/code-quality/c33004.md

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---
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title: c33004
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description: C33004 warning for VARIANTs
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keywords: c33004
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author: hwisungi
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ms.author: hwisungi
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ms.date: 06/20/2020
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ms.topic: reference
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f1_keywords: ["C33004"]
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helpviewer_keywords: ["C33004"]
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dev_langs: ["C++"]
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---
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# C33004
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> Warning C33004: VARIANT 'var', which is marked as _Out_ was cleared before being initialized (expression 'expr')
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This warning is triggered when a VARIANT parameter with \_Out\_ SAL annotation, which may not be
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to be initialized on input, is passed to an API such as VariantClear that expects an initialized VARIANT.
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## Example
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```cpp
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#include <Windows.h>
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void t2(_Out_ VARIANT* pv)
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{
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// ......
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VariantClear(pv); // C33004
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// ......
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}
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```
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These warnings are corrected by ensuring VariantClear is called only for a properly initialized VARIANT:
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```cpp
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#include <Windows.h>
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void t2(_Out_ VARIANT* pv)
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{
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VariantInit(pv);
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// ......
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VariantClear(pv); // OK
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// ......
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}
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```
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## See also
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[C33001](/cpp/code-quality/c33001)
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[C33005](/cpp/code-quality/c33005)

‎docs/code-quality/c33005.md

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---
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title: c33005
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description: C33005 warning for VARIANTs
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keywords: c33005
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author: hwisungi
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ms.author: hwisungi
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ms.date: 06/20/2020
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ms.topic: reference
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f1_keywords: ["C33005"]
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helpviewer_keywords: ["C33005"]
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dev_langs: ["C++"]
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---
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# C33005
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> Warning C33005: VARIANT 'var' was provided as an input or input/output parameter but was not initialized (expression 'expr')
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This warning is triggered when an uninitialized VARIANT is passed to a function as input only or input/output
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parameter - for example, a pass-by-refrence parameter without an \_Out\_ SAL annotation.
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## Example
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```cpp
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#include <Windows.h>
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void bar(VARIANT* v); // v is assumed to be input/output
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void foo()
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{
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VARIANT v;
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bar(&v); // C33005
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// ......
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VariantClear(&v); // OK, assumed to be initialized by bar
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}
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```
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These warnings are corrected by ensuring to initialize the VARIANT before passing it to a function
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as input-only or input/output.
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```cpp
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#include <Windows.h>
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void bar(VARIANT* v); // v is assumed to be input/output
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void foo()
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{
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VARIANT v;
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VariantInit(&v);
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bar(&v); // OK
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// ......
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VariantClear(&v); // OK, assumed to be initialized by bar
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}
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```
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## See also
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[C33001](/cpp/code-quality/c33001)
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[C33004](/cpp/code-quality/c33004)

‎docs/code-quality/c33010.md

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---
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title: c33010
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description: C33010 warning for enums
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keywords: c33010
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author: hwisungi
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ms.author: hwisungi
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ms.date: 06/20/2020
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ms.topic: reference
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f1_keywords: ["C33010"]
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helpviewer_keywords: ["C33010"]
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dev_langs: ["C++"]
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---
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# C33010
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> Warning C33010: Unchecked lower bound for enum 'enum' used as index.
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This warning is triggered for an enum that is used as an index into an array,
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if the upper bound is checked for its value, but not the lower bound.
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## Example
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Code using enumerated types as indexes for arrays will often check for the upper bound
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in order to ensure the index is not out of range. Because an enum variable is signed by default,
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it can have a negative value. If it is used as an index into an array of values or an array of function pointers,
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a negative value can allow arbitrary memory to be read, used, or even executed.
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```cpp
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typedef void (*PFN)();
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enum class Index
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{
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Zero,
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One,
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Two,
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Three,
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Max
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};
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void foo(Index idx, PFN(&functions)[5])
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{
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if (idx > Index::Max)
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return;
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auto pfn = functions[static_cast<int>(idx)]; // C33010
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if (pfn != nullptr)
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(*pfn)();
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// ......
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}
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```
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These warnings are corrected by checking the index value for lower bound as well:
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```cpp
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typedef void (*PFN)();
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enum class Index
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{
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Zero,
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One,
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Two,
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Three,
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Max
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};
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void foo(Index idx, PFN(&functions)[5])
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{
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if (idx < Index::Zero || idx > Index::Max)
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return;
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auto pfn = functions[static_cast<int>(idx)]; // OK
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if (pfn != nullptr)
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(*pfn)();
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// ......
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}
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```
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## See also
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[C33011](/cpp/code-quality/c33011)

‎docs/code-quality/c33011.md

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---
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title: c33011
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description: C33011 warning for enums
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keywords: c33011
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author: hwisungi
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ms.author: hwisungi
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ms.date: 06/20/2020
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ms.topic: reference
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f1_keywords: ["C33011"]
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helpviewer_keywords: ["C33011"]
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dev_langs: ["C++"]
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---
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# C33011
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> Warning C33011: Unchecked upper bound for enum 'enum' used as index.
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This warning is triggered when the lower bound of the enum used as index into an array is checked,
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but the upper bound is not checked.
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This warning is triggered for an enum that is used as an index into an array,
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if the lower bound is checked for its value, but not the upper bound.
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## Example
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Code that uses enumerated types as indexes for arrays must check the enum value for both lower and
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upper bounds. If the enum value is checked only for the lower bound before used to index into an array of values
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or an array of function pointers, then it can allow arbitrary memory to be read, used, or even executed.
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```cpp
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typedef void (*PFN)();
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enum class Index
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{
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Zero,
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One,
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Two,
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Three,
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Max
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};
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void foo(Index idx, PFN(&functions)[5])
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{
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if (idx < Index::Zero)
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return;
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auto pfn = functions[static_cast<int>(idx)]; // C33011
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if (pfn != nullptr)
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(*pfn)();
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// ......
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}
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```
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These warnings are corrected by declaring the enum as enum class:
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```cpp
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typedef void (*PFN)();
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enum class Index
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{
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Zero,
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One,
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Two,
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Three,
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Max
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};
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void foo(Index idx, PFN(&functions)[5])
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{
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if (idx < Index::Zero || idx > Index::Max)
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return;
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auto pfn = functions[static_cast<int>(idx)]; // OK
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if (pfn != nullptr)
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(*pfn)();
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// ......
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}
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```
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## See also
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[C33010](/cpp/code-quality/c33010)

‎docs/code-quality/c33020.md

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---
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title: c33020
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description: C33020 warning for HRESULTs
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keywords: c33020
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author: hwisungi
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ms.author: hwisungi
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ms.date: 06/20/2020
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ms.topic: reference
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f1_keywords: ["C33020"]
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helpviewer_keywords: ["C33020"]
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dev_langs: ["C++"]
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---
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# C33020
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> Warning C33020: Likely incorrect HRESULT usage detected.
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This is high-confidence warning indicating that HRESULT-returning function returns FALSE or false.
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## Example
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```cpp
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#include <Windows.h>
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HRESULT foo()
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{
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// ......
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return FALSE; // C33020
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}
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```
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These warnings are corrected by using proper HRESULT value:
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```cpp
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#include <Windows.h>
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HRESULT foo()
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{
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// ......
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return E_FAIL; // OK
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}
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```
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## See also
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[C33022](/cpp/code-quality/c33022)

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