Thread: Global variable problem (function related)

  1. #1
    Registered User Ktulu's Avatar
    Join Date
    Oct 2006

    Global variable problem (function related)

    I'm trying to create some kind of error system but I fail and I'm asking if one of you could help me. Here's the deal:
    When one of my functions is about to return FALSE (or -1) I'll make it call a SetError function first (with a string as paramater).
    When the programs notice that the function returns FALSE it will then call the GetError function and display the error to the user.
    My question: How could I create this without using a global variable?

    Here is a simple code example where I hope you see what I mean:

    //In "Error.hpp"
    # include <windows.h>
    LPSTR StrGlobalError = NULL;//This is what I'm trying to avoid.
    VOID SetErrorString ( LPSTR StrError )
        StrGlobalError = StrError;
    LPSTR StrGetErrorString()//Using a global variable like this makes this function useless
        return StrGlobalError;
    Thanks, Ktulu.
    This parameter is reserved

  2. #2
    Registered /usr
    Join Date
    Aug 2001
    Newport, South Wales, UK
    What's the problem with it being global exactly?

    If you think about how the Win32 error functions work, an integer describing the error is held within memory and retrieved upon request. Therefore, it is a global. The strings aren't, they're pulled out of a resource file and (maybe/maybe not) destroyed after being copied to an application-supplied buffer.
    Last edited by SMurf; 05-24-2007 at 05:18 PM.

  3. #3
    Frequently Quite Prolix dwks's Avatar
    Join Date
    Apr 2005
    I would either use a static global variable and put your error-handling code in a separate source file, or use something like this hack:
    static char **get_error_buffer(void) {
        static char *error = "no error";
        return &error;
    Actually, I'd probably use the former because the latter looks wierd.

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  4. #4
    Malum in se abachler's Avatar
    Join Date
    Apr 2007
    DWORD GetError(){
         return ErrorFunc(0,0);
    DWORD SetError(DWORD Error){
         return ErrorFunc(1,Error);
    DWORD ErrorFunc(DWORD RW , DWORD Error){
         static ErrorCode;
              case 0:
                   return ErrorCode;
              case 1:
                   ErrorCode = Error;
                   return 0;
         return 0;
    No global variable, simple interface. GetError() returns the last set error code, SetError(X) sets the error code to X. Do not call ErrorFunc directly unless you understand what its doing.
    Last edited by abachler; 05-25-2007 at 09:59 AM.

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