A question about system temp file

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C++

char* TempPath()
{
     char *Buffer;
     DWORD dwRet;
     dwRet   = GetTempPath(0,NULL);
     if( dwRet == 0 )
     {
         printf("GetCurrentDirectory failed (%d)\n", GetLastError());
         return NULL;
     }
     Buffer = (char *)malloc(sizeof(char)*dwRet);
     memset(Buffer,0,dwRet*sizeof(char));
     GetTempPath(dwRet,Buffer);
     return add_slash(Buffer);
}

	char* purPath = TempPath();
	sprintf(purPath,"%sTest.txt",purPath);
	fout = fopen(purPath, "r");

when i build the code to exe,and double click exe to run application,it throw error as below:

C#

Try to read or write protected memory. This usually indicates that other memory is corrupt

why?
i want to hide Test.txt file path,so use the system temp file to store filepath.
how can i achieve the same purpose and not throw memory error?

What I have tried:

if i change the temp file path to debug dirctory,it runs ok.

Posted 13-Jun-16 17:59pm

xuyunhai

Updated 13-Jun-16 19:55pm

v2

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2 solutions

Solution 1

Have a look at this example: Creating and Using a Temporary File (Windows)[^]
Look at this line:

C#

 //  Gets the temp path env string (no guarantee it's a valid path).
dwRetVal = GetTempPath(MAX_PATH,          // length of the buffer
                       lpTempPathBuffer); // buffer for path

lpTempPathBuffer

is where the temporary path name is placed.
Now -- You must also allocate sufficient space for the filename in your buffer else this line will fail:

C++

sprintf(purPath,"%sTest.txt",purPath);

You are copying the buffer plus some extra bytes into the original buffer.
That is why in the example the buffer is created as length MAX_PATH.

Posted 13-Jun-16 18:16pm

User 59241

Updated 13-Jun-16 21:05pm

v5

Comments

xuyunhai 14-Jun-16 1:27am

you can try to invoke TempPath method,return correct path.

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xuyunhai · Accepted Answer · 2016-06-13T19:55:00

Solution 2

C++

char* tempPath = TempPath();
char purPath[256];
if(tempPath != NULL)
{
    strcpy(purPath, tempPath);
}
    sprintf(purPath,"%sTest.txt",purPath);
fout = fopen(purPath, "r");

Posted 13-Jun-16 19:55pm

xuyunhai