Why same path in RegOpenKeyEx() and RegQueryValueEx() is not working?

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Hello everyone,

I try to read a value from registry, I try this code
Note
: based on Windows7
: using MSVC++2010 as tool

C++

#include <windows.h>
#include <malloc.h>
#include <stdio.h>

#define TOTALBYTES    8192


void main()
{
    DWORD BufferSize = TOTALBYTES;
    DWORD cbData;
    DWORD dwRet;
	HKEY result;

    PPERF_DATA_BLOCK PerfData = (PPERF_DATA_BLOCK) malloc( BufferSize );

	dwRet = RegOpenKeyEx(HKEY_LOCAL_MACHINE,
							TEXT("HARDWARE\\DESCRIPTION\\System\\CentralProcessor\\0\\"),
							0,
							KEY_ALL_ACCESS,
							&result
		);
    if( dwRet == ERROR_SUCCESS )
        printf("\n\RegOpenKeyEx result : %d, function successed\n", &result);
    else printf("\nRegOpenKeyEx failed (%d)\n", dwRet);
	
	dwRet = RegQueryValueEx( HKEY_LOCAL_MACHINE,
                             TEXT("HARDWARE\\DESCRIPTION\\System\\CentralProcessor\\0\\~MHz"),
                             NULL,
                             NULL,
                             (LPBYTE) PerfData,
                             &cbData );
	if( dwRet == ERROR_SUCCESS )
        printf("\n\nRegQueryValueEx result(~MHz) %d, function successed\n", &cbData);
    else printf("\nRegQueryValueEx(~MHz) failed (%d)\n", dwRet);

	dwRet = RegQueryValueEx( HKEY_LOCAL_MACHINE,
                             TEXT("HARDWARE\\DESCRIPTION\\System\\CentralProcessor\\0"),
                             NULL,
                             NULL,
                             (LPBYTE) PerfData,
                             &cbData);
	if( dwRet == ERROR_SUCCESS )
        printf("\n\nRegQueryValueEx result %d, function successed\n", &cbData);
    else printf("\nRegQueryValueEx failed (%d)\n", dwRet);

	dwRet = RegCloseKey(result);
	if( dwRet == ERROR_SUCCESS )
        printf("\n\nRegCloseKey successed\n");
    else printf("\nRegCloseKey failed (%d)\n", dwRet);


	system("pause");
}

Why two paths in RegQueryValueEx() is not working, as it works on RegOpenKeyEx() and RegCloseKey()?

Posted 21-Dec-11 23:25pm

windyl3ig

Updated 21-Dec-11 23:40pm

Malli_S

v2

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Comments

CPallini 22-Dec-11 5:35am

What is the error return value (dwRet)?

windyl3ig 22-Dec-11 5:52am

no, not return value but it show,

nRegQueryValueEx(~MHz) failed (2)
nRegQueryValueEx failed (2)

That means, File not Found, why file is not found? because I used the same path with RegOpenKeyEx()

Jochen Arndt 22-Dec-11 5:58am

Why you do not pass the opened key handle: RegQueryValueEx(result, "~MHz", ...)?

windyl3ig 22-Dec-11 6:22am

That 's not work too, 2 still be returned.

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CPallini · Accepted Answer · 2011-12-22T00:24:00

Because, as already noted by Jochen Arndt, RegQueryValueEx does NOT work that way: you misunderstood the function documentation. Change, for instance

windyl3ig wrote:

VB

dwRet = RegQueryValueEx( HKEY_LOCAL_MACHINE,
                             TEXT("HARDWARE\\DESCRIPTION\\System\\CentralProcessor\\0\\~MHz"),
                             NULL,
                             NULL,
                             (LPBYTE) PerfData,
                             &cbData );

to

C++

DWORD dwMHz;
cbData = sizeof(dwMHz);
dwRet = RegQueryValueEx( result,
                         TEXT("~MHz"),
                         NULL,
                         NULL,
                         (LPBYTE) &dwMHz,
                         &cbData );