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Useful macros for pointer verification

, 20 Oct 2002 128.8K 467 46
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A few macros to validate pointers passed to functions.
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Introduction

Most know the useful macros provided by various libraries named ASSERT, VERIFY (and similar) which just validates the provided argument. If the validation evaluates to false then a debug notification is raised.

In many cases this is sufficient for simple verifications but validating pointers is not the strength of this methods. Look at this example:

void MyFunction(LPSOMESTRUCT pData)
{
  ASSERT(pData != NULL);
  // ... more code
}
When you pass a NULL pointer to this function it will correctly detect it, but what if you pass 0xcdcdcdcd ? Its not NULL and its most probably not a valid address either. ASSERT will not catch it and you application will throw an exception.

More Macros

Here is a more advanced solution required. One possible solution is the use of the functions provided by the Windows API: IsBadReadPtr(), IsBadWritePtr(), IsBadStringPtr(). These functions take a memory location and a size as arguments and verify that the calling process really has read and/or write access to the location. It might be that the memory at the location is only partially accessible from your process, or that the memory is read or write only. These functions also detect this situations.

I've wrapped this functions into handy macros which you can use similar to the ASSERT and VERIFY macros.

#ifdef _DEBUG

#define VERIFY_ISWRITEPOINTER(a) \
       { if(::IsBadWritePtr(a, sizeof(LPDWORD))) \
		{ ::OutputDebugString(_T("Parameter ") _T(#a) \
		_T(" is not a valid write pointer\r\n"));}}
#define VERIFY_ISREADPOINTER(a) \
		{ if(::IsBadReadPtr(a, sizeof(LPDWORD)))\
		{ ::OutputDebugString(_T("Parameter ") _T(#a) \
		_T(" is not a valid read pointer\r\n"));}}

#define VERIFY_ISWRITEDATA(a, l)\
		{ if(::IsBadWritePtr(a, l)) \
		{ ::OutputDebugString(_T("Parameter ") _T(#a) \
		_T(" is not a valid write area\r\n"));}}
#define VERIFY_ISREADDATA(a, l)\
		{ if(::IsBadReadPtr(a, l))  \
		{ ::OutputDebugString(_T("Parameter ") _T(#a) \
		_T(" is not a valid read area\r\n"));}}

#define ASSERT_ISWRITEPOINTER(a)\
		{ if(::IsBadWritePtr(a, sizeof(LPDWORD))) \
		{ ::OutputDebugString(_T("Parameter ") _T(#a) \
		_T(" is not a valid write pointer\r\n")); ASSERT(false);}}
#define ASSERT_ISREADPOINTER(a)\
		{ if(::IsBadReadPtr(a, sizeof(LPDWORD)))  \
		{ ::OutputDebugString(_T("Parameter ") _T(#a) \
		_T(" is not a valid read pointer\r\n")); ASSERT(false);}}

#define ASSERT_ISWRITEDATA(a, l)\
		{ if(::IsBadWritePtr(a, l)) \
		{ ::OutputDebugString(_T("Parameter ") _T(#a) \
		_T(" is not a valid write area\r\n")); ASSERT(false);}}
#define ASSERT_ISREADDATA(a, l)		{ if(::IsBadReadPtr(a, l))  \
		{ ::OutputDebugString(_T("Parameter ") _T(#a)\
		_T(" is not a valid read area\r\n")); ASSERT(false);}}

#else

#define VERIFY_ISWRITEPOINTER(a)
#define VERIFY_ISREADPOINTER(a)	

#define VERIFY_ISWRITEDATA(a, l)
#define VERIFY_ISREADDATA(a, l)	

#define ASSERT_ISWRITEPOINTER(a)
#define ASSERT_ISREADPOINTER(a)

#define ASSERT_ISWRITEDATA(a, l)
#define ASSERT_ISREADDATA(a, l)

#endif

Our sample from before can be changed to this:

void MyFunction(LPSOMESTRUCT pData)
{
  ASSERT_ISREADDATA(pData, sizeof(SOMESTRUCT));
  // ... more code
}
Now it will correctly assert when you pass the address 0xcdcdcdcd or any other location from which the function can not read at least sizeof(SOMESTRUCT) bytes and the debug output will show "Parameter pData is not a valid read area".

I have found this to be a valuable tool when you write functions which take in or out pointers. Many problems related to bad pointers can easily be cured by using these validation macros.

Compatibility

This is compatible with any Windows version without restriction. It can be used with any Visual C++ version and all eVC versions. Anyway, using the macros is your responsability Smile | :)

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

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Comments and Discussions

 
GeneralGuaranteed Multithreading Problems Pin
pg--az12-Jun-09 3:22
memberpg--az12-Jun-09 3:22 
GeneralThese IsBadxxx functions are dangerous! Pin
AaronJRidout31-Oct-07 6:38
memberAaronJRidout31-Oct-07 6:38 
GeneralRe: These IsBadxxx functions are dangerous! Pin
Andreas Saurwein Franci Gonalves31-Oct-07 6:56
memberAndreas Saurwein Franci Gonalves31-Oct-07 6:56 
GeneralRe: These IsBadxxx functions are dangerous! Pin
Blake Miller2-May-08 6:29
memberBlake Miller2-May-08 6:29 
Generalevc support Pin
hillol sarker12-Oct-04 23:17
memberhillol sarker12-Oct-04 23:17 
GeneralRe: evc support Pin
Liby Baby6-Jul-05 19:17
sussLiby Baby6-Jul-05 19:17 
Generalnew -> delete -> valid pointer Pin
Thomas Knauth18-Nov-02 6:14
memberThomas Knauth18-Nov-02 6:14 
GeneralRe: new -> delete -> valid pointer Pin
Andreas Saurwein18-Nov-02 6:45
memberAndreas Saurwein18-Nov-02 6:45 
No it does not. Simply because it does not make heap/stack checks. And so far the pSomething pointer is pointing to a valid memory area, except if it happens that your memory manager really frees the block where your 200 chars are located. May happen, may not happen.
You must add extra heap checking code for this kind of errors.
[edit]
It will however work when you use functions like GlobalAlloc()/GlobalFree() for your memory allocations instead of new/delete or malloc/free.
[/edit]


I don't think this is a serious possesion, and the evil most likely comes from your hand. Colin J Davies, The Lounge


GeneralRe: new -> delete -> valid pointer Pin
Philippe Lhoste2-Dec-02 5:56
memberPhilippe Lhoste2-Dec-02 5:56 
GeneralRe: new -> delete -> valid pointer Pin
Andreas Saurwein2-Dec-02 13:04
memberAndreas Saurwein2-Dec-02 13:04 
Generalsizeof(LPDWORD) Pin
Martin Bach22-Oct-02 2:11
memberMartin Bach22-Oct-02 2:11 
GeneralRe: sizeof(LPDWORD) Pin
Andreas Saurwein22-Oct-02 3:54
memberAndreas Saurwein22-Oct-02 3:54 
GeneralRe: sizeof(LPDWORD) Pin
Martin Bach22-Oct-02 5:47
memberMartin Bach22-Oct-02 5:47 
GeneralRe: sizeof(LPDWORD) Pin
Andreas Saurwein22-Oct-02 7:14
memberAndreas Saurwein22-Oct-02 7:14 
GeneralRe: sizeof(LPDWORD) Pin
Martin Bach22-Oct-02 21:19
memberMartin Bach22-Oct-02 21:19 
GeneralRe: sizeof(LPDWORD) Pin
Anonymous24-Oct-02 5:26
sussAnonymous24-Oct-02 5:26 
GeneralRe: sizeof(LPDWORD) Pin
Andreas Saurwein24-Oct-02 9:43
memberAndreas Saurwein24-Oct-02 9:43 
GeneralRe: sizeof(LPDWORD) Pin
Anonymous24-Oct-02 14:01
sussAnonymous24-Oct-02 14:01 
GeneralRe: sizeof(LPDWORD) Pin
Andreas Saurwein25-Oct-02 3:19
memberAndreas Saurwein25-Oct-02 3:19 
GeneralRe: sizeof(LPDWORD) Pin
Anonymous25-Oct-02 6:17
sussAnonymous25-Oct-02 6:17 
GeneralRe: sizeof(LPDWORD) Pin
Andreas Saurwein25-Oct-02 6:33
memberAndreas Saurwein25-Oct-02 6:33 
GeneralRemove MFC dependency... Pin
Nguyen Binh21-Oct-02 17:47
memberNguyen Binh21-Oct-02 17:47 
GeneralRe: Remove MFC dependency... Pin
KarstenK21-Oct-02 21:42
memberKarstenK21-Oct-02 21:42 
GeneralRe: Remove MFC dependency... Pin
Andreas Saurwein21-Oct-02 23:55
memberAndreas Saurwein21-Oct-02 23:55 
GeneralRe: Remove MFC dependency... Pin
Nguyen Binh22-Oct-02 2:37
memberNguyen Binh22-Oct-02 2:37 
GeneralRe: Remove MFC dependency... Pin
Andreas Saurwein22-Oct-02 4:00
memberAndreas Saurwein22-Oct-02 4:00 
GeneralRe: Remove MFC dependency... Pin
Nguyen Binh23-Oct-02 1:02
memberNguyen Binh23-Oct-02 1:02 
GeneralRe: Remove MFC dependency... Pin
Andreas Saurwein23-Oct-02 1:52
memberAndreas Saurwein23-Oct-02 1:52 
GeneralRe: Remove MFC dependency... Pin
Armen Hakobyan21-Oct-02 23:54
memberArmen Hakobyan21-Oct-02 23:54 
GeneralRe: Remove MFC dependency... Pin
.:fl0yd:.14-Jun-03 14:33
member.:fl0yd:.14-Jun-03 14:33 
General0.4 kb Pin
Anonymous21-Oct-02 16:32
sussAnonymous21-Oct-02 16:32 
GeneralRe: 0.4 kb Pin
Andreas Saurwein21-Oct-02 23:56
memberAndreas Saurwein21-Oct-02 23:56 
GeneralRe: 0.4 kb Pin
Norm Almond22-Oct-02 1:06
memberNorm Almond22-Oct-02 1:06 
Generalverify vs trace Pin
Hugo Hallman21-Oct-02 6:55
memberHugo Hallman21-Oct-02 6:55 
GeneralRe: verify vs trace Pin
Andreas Saurwein21-Oct-02 7:10
memberAndreas Saurwein21-Oct-02 7:10 
GeneralHelpfull Pin
Roger Allen21-Oct-02 6:48
memberRoger Allen21-Oct-02 6:48 
GeneralTwo in one :) Pin
Armen Hakobyan21-Oct-02 6:37
memberArmen Hakobyan21-Oct-02 6:37 
GeneralRe: Two in one :) Pin
Andreas Saurwein21-Oct-02 7:12
memberAndreas Saurwein21-Oct-02 7:12 
GeneralRe: Two in one :) Pin
Roger Allen23-Oct-02 3:38
memberRoger Allen23-Oct-02 3:38 
GeneralFormatting Pin
Giles21-Oct-02 6:29
memberGiles21-Oct-02 6:29 
GeneralRe: Formatting Pin
Andreas Saurwein21-Oct-02 7:15
memberAndreas Saurwein21-Oct-02 7:15 
GeneralRe: Formatting Pin
Giles21-Oct-02 9:05
memberGiles21-Oct-02 9:05 

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