MSDN 上的Hook例子2

/******************************************************
*  EXAMPLE  2                                        *
*                                                    *
*  This application illustrates several ways to use  *
*  debugging hook functions with the new debug       *
*  versions of the C runtime libraries. To add some  *
*  realism, it has a few elements of an actual       *
*  application, including two bugs.                  *
*                                                    *
*  The program stores birthdate information in a     *
*  linked list of Client blocks. A Client-dump hook  *
*  function validates the birthday data and reports  *
*  the contents of the Client blocks. An allocation  *
*  hook function logs heap operations to a text file,*
*  and the report hook function logs reports to the  *
*  same text file.                                   *
*                                                    *
*  NOTE: The allocation hook function explicitly     *
*  excludes CRT blocks (the memory allocated         *
*  internally by the C runtime library) from its log.*
*  It is important to understand why! The hook       *
*  function uses fprintf( ) to write to the log file,*
*  and fprintf( ) allocates a CRT block. If CRT      *
*  blocks   were not excluded in this case, an       *
*  endless loop would be created in which fprintf( ) *
*  would cause the hook function to be called, and   *
*  the hook would in turn call fprintf( ), which     *
*  would cause the hook to be called again, and so   *
*  on. The moral is:                                 *
*                                                    *
*  IF YOUR ALLOCATION HOOK USES ANY C RUNTIME        *
*  FUNCTION THAT ALLOCATES MEMORY, THE HOOK MUST     *
*  IGNORE CRT-TYPE ALLOCATION OPERATIONS!            *
*                                                    *
*  HINT: If you want to be able to report CRT-type   *
*  blocks in your allocation hook, use Windows API   *
*  functions for formatting and output, instead of C *
*  runtime functions. Since the Windows APIs do not  *
*  use the CRT heap, they will not trap your hook in *
*  an endless loop.                                  *
*                                                    *
*  BUGS: There are two bugs in the program below,    *
*  which the debug heap features identify in several *
*  ways. One bug is that the birthDay.Name field is  *
*  not large enough to hold several of the test      *
*  names. The field should be larger, and strncpy( ) *
*  should be used in place of strcpy( ). The second  *
*  bug is that the while( ) loop in the              *
*  printRecords( ) function should not end until     *
*  HeadPtr itself == NULL. This bug results not only *
*  in an incomplete display of birthdays, but also in*
*  a memory leak. In addition to these two bugs,     *
*  Gauss' birthday data is out of range (April 30,   *
*  not 32).                                          *
******************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <malloc.h>
#include <time.h>
#include <crtdbg.h>

/******************************************************
*  DATA DECLARATIONS AND DEFINES                     *
******************************************************/

// The following arrays provide test data for the
// example program:
// 下面的数组提供本程序的测试数据
const char * Names[] =
{
"George Washington",
"Thomas Jefferson",
"Carl Friedrich Gauss",
"Ludwig van Beethoven",
"Thomas Carlyle"
} ;

const int Dates[] =
{
1732,  2, 11,
1743,  4, 13,
1777,  4, 32,
1795, 12,  4,
1770, 12, 16
} ;

#define  TEST_RECS            5
// A generic sort of linked-list data structure, in
// this case for birthdays:
typedef struct BirthdayStruct
{
struct BirthdayStruct * NextRec;
int   Year;
int   Month;
int   Day;
char  Name[20];
} birthDay;

birthDay * HeadPtr;
birthDay * TailPtr;

#define  FILE_IO_ERROR        0
#define  OUT_OF_MEMORY        1

#define  TRUE                 7
#define  FALSE                0

// Macros for setting or clearing bits in the CRT debug flag
#ifdef _DEBUG
#define  SET_CRT_DEBUG_FIELD(a)   _CrtSetDbgFlag((a) | _CrtSetDbgFlag(_CRTDBG_REPORT_FLAG))
#define  CLEAR_CRT_DEBUG_FIELD(a) _CrtSetDbgFlag(~(a) & _CrtSetDbgFlag(_CRTDBG_REPORT_FLAG))
#else
#define  SET_CRT_DEBUG_FIELD(a)   ((void) 0)
#define  CLEAR_CRT_DEBUG_FIELD(a) ((void) 0)
#endif

/******************************************************
*  SPECIAL-PURPOSE ROUTINES                          *
******************************************************/

/* ERROR HANDLER
Handling serious errors gracefully is a real test of
craftsmanship. This function is just a stub; it
doesn't really handle errors.
*/
void FatalError( int ErrType )
{
exit( 1 );
}

/* MEMORY ALLOCATION FUNCTION
The createRecord function allocates memory for a new
birthday record, fills in the structure members, and
then adds the record to a linked list. In debug
builds, it makes these allocations in Client blocks.
If memory is not available, it calls the error
handler.
*/
void createRecord(
const int    Year,
const int    Month,
const int    Day,
const char * Name
#ifdef _DEBUG
,  const unsigned char * szFileName, int nLine
#endif
)
{
birthDay * ptr;
size_t n;

n = sizeof( struct BirthdayStruct );
ptr = (birthDay *) _malloc_dbg( n, _CLIENT_BLOCK, szFileName, nLine );
if( ptr == NULL )
FatalError( OUT_OF_MEMORY );
ptr->Year = Year;
ptr->Month = Month;
ptr->Day = Day;
strcpy( ptr->Name, Name );

ptr->NextRec = NULL;
if ( HeadPtr == NULL ) // 1st record in linked list?
HeadPtr = ptr;
else
TailPtr->NextRec = ptr;
TailPtr = ptr;
}

/* BIRTHDAY DISPLAY FUNCTION
This function traverses the linked list, displays the
birthday data, and then frees the memory blocks used
to store the birthdays.
*/
void printRecords( )
{
birthDay * ptr;
char *months[] = {
"", "January", "February", "March", "April", "May", "June", "July",
"August", "September", "October", "November", "December" };

if ( HeadPtr == NULL ) // Do nothing if list empty
return;

printf( "\n\nThis is the birthday list:\n" );
while ( HeadPtr->NextRec != NULL )
{
printf( "   %s was born on %s %d, %d.\n",
HeadPtr->Name, months[HeadPtr->Month], HeadPtr->Day, HeadPtr->Year );
ptr = HeadPtr->NextRec;
_free_dbg( HeadPtr, _CLIENT_BLOCK );
HeadPtr = ptr;
}
}

/******************************************************
*  DEBUG C RUNTIME LIBRARY HOOK FUNCTIONS AND DEFINES*
******************************************************/
#ifdef _DEBUG
#define  createRecord(a, b, c, d) \
createRecord(a, b, c, d, __FILE__, __LINE__)
FILE *logFile;                // Used to log allocation information
const char lineStr[] = { "---------------------------------------\
--------------------------------------\n"  };

/* CLIENT DUMP HOOK FUNCTION
A hook function for dumping a Client block usually
reports some or all of the contents of the block in
question.  The function below also checks the data
in several ways, and reports corruption or
inconsistency as an assertion failure.
*/
void __cdecl MyDumpClientHook(
void * pUserData,
size_t nBytes
)
{
birthDay * bday;

bday = (birthDay *) pUserData;

_RPT4( _CRT_WARN, "   The birthday of %s is %d/%d/%d.\n",
bday->Name, bday->Month, bday->Day, bday->Year );
_ASSERTE( ( bday->Day > 0 ) && ( bday->Day < 32 ) );
_ASSERTE( ( bday->Month > 0 ) && ( bday->Month < 13 ) );
_ASSERTE( ( bday->Year > 0 ) && ( bday->Year < 1996 ) );
}

/* ALLOCATION HOOK FUNCTION
An allocation hook function can have many, many
different uses. This one simply logs each allocation
operation in a file.
*/
int __cdecl MyAllocHook(
int      nAllocType,
void   * pvData,
size_t   nSize,
int      nBlockUse,
long     lRequest,
const unsigned char * szFileName,
int      nLine
)
{
char *operation[] = { "", "allocating", "re-allocating", "freeing" };
char *blockType[] = { "Free", "Normal", "CRT", "Ignore", "Client" };

if ( nBlockUse == _CRT_BLOCK ) // Ignore internal
// C runtime library
// allocations
return( TRUE );

_ASSERT( ( nAllocType > 0 ) && ( nAllocType < 4 ) );
_ASSERT( ( nBlockUse >= 0 ) && ( nBlockUse < 5 ) );

fprintf( logFile,
"Memory operation in %s, line %d: %s a %d-byte '%s' block (# %ld)\n",
szFileName, nLine, operation[nAllocType], nSize,
blockType[nBlockUse], lRequest );
if ( pvData != NULL )
fprintf( logFile, " at %X", pvData );

return( TRUE );   // Let memory operation proceed
}

/* REPORT HOOK FUNCTION
Again, report hook functions can serve a very wide
variety of purposes. This one logs error and
assertion failure debug reports in the log file,
along with 'Damage' reports about overwritten
memory.

By setting the retVal parameter to zero, we are
instructing _CrtDbgReport to return zero, which
causes execution to continue. If we want the
function to start the debugger, we should have
_CrtDbgReport return one.
*/
int MyReportHook(
int   nRptType,
char *szMsg,
int  *retVal
)
{
char *RptTypes[] = { "Warning", "Error", "Assert" };

if ( ( nRptType > 0 ) || ( strstr( szMsg, "DAMAGE" ) ) )
fprintf( logFile, "%s: %s", RptTypes[nRptType], szMsg );

retVal = 0;

return( TRUE );  // Allow report to be made as usual

}
#endif              // End of #ifdef _DEBUG

/******************************************************
*  MAIN FUNCTION                                     *
******************************************************/
void main( )
{
int i, j;

#ifdef _DEBUG
_CrtMemState checkPt1;
char timeStr[10], dateStr[10];         // Used to set up log file

// Send all reports to STDOUT, since this example is
// a console app
_CrtSetReportMode(_CRT_WARN, _CRTDBG_MODE_FILE);
_CrtSetReportFile(_CRT_WARN, _CRTDBG_FILE_STDOUT);
_CrtSetReportMode(_CRT_ERROR, _CRTDBG_MODE_FILE);
_CrtSetReportFile(_CRT_ERROR, _CRTDBG_FILE_STDOUT);
_CrtSetReportMode(_CRT_ASSERT, _CRTDBG_MODE_FILE);
_CrtSetReportFile(_CRT_ASSERT, _CRTDBG_FILE_STDOUT);

// Set the debug heap to report memory leaks when
// the process terminates,and to keep freed blocks
// in the linked list.
SET_CRT_DEBUG_FIELD( _CRTDBG_LEAK_CHECK_DF | _CRTDBG_DELAY_FREE_MEM_DF );

// Open a log file for the hook functions to use
logFile = fopen( "MEM-LOG.TXT", "w" );
if ( logFile == NULL )
FatalError( FILE_IO_ERROR );
_strtime( timeStr );
_strdate( dateStr );
fprintf( logFile,
"Memory Allocation Log File for Example Program, run at %s on %s.\n",
timeStr, dateStr );
fputs( lineStr, logFile );

// Install the hook functions
_CrtSetDumpClient( MyDumpClientHook );
_CrtSetAllocHook( MyAllocHook );
_CrtSetReportHook( MyReportHook );

#endif                     // End of #ifdef _DEBUG

HeadPtr = NULL;

// Create a trial birthday record.
createRecord( 1749, 3, 23, "Pierre de Laplace" );

// Check the debug heap, and dump the new birthday
// record. --Note that debug C runtime library
// functions such as _CrtCheckMemory( ) and
// _CrtMemDumpAllObjectsSince( ) automatically
// disappear in a release build.
_CrtMemDumpAllObjectsSince( NULL );
_CrtCheckMemory( );
_CrtMemCheckpoint( &checkPt1 );

// Since it all works so far, create more records
for ( i = 0, j = 0; i < TEST_RECS; i++, j+=3 )
createRecord( Dates[j], Dates[j+1], Dates[j+2], Names[i] );

// Examine the results
_CrtMemDumpAllObjectsSince( &checkPt1 );
_CrtMemCheckpoint( &checkPt1 );
_CrtMemDumpStatistics( &checkPt1 );
_CrtCheckMemory( );

// This fflush needs to be removed...
fflush( logFile );

// Now try displaying the records, which frees the
// memory being used
printRecords( );

// OK, time to go. Did I forget to turn out any
// lights? I could check explicitly using
// _CrtDumpMemoryLeaks( ), but I have set
// _CRTDBG_LEAK_CHECK_DF, so the C runtime library
// debug heap will automatically alert me at exit of
// any memory leaks.

#ifdef _DEBUG
fclose( logFile );
#endif
}