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From Andrew Black <>
Subject Re: [patch] exec utility windows port
Date Fri, 18 Aug 2006 21:11:01 GMT

Attached is a patch that adds return value checking to the CloseHandle 
and WaitForSingleObject calls added in Farid's patch.

	* exec.cpp [_WIN32 || _WIN64] (exec_file): Check return value from 
calls to CloseHandle and WaitForSingleObject.

Martin Sebor wrote:
> Andrew Black wrote:
>> I have a couple thoughts about this proposed patch.
>> The first observation is related to the warn_last_error change.  It 
>> appears to me that the type of error_text should be changed from 
>> LPTSTR to TCHAR, eliminating the need for the typecast in the call to 
>> FormatMessage.
> TCHAR is the same thing as char and LPTSTR is the same thing as char*
> as far as we're concerned. The names are Microsoft's harebrained idea
> for an internationalized API. When FormatMessage is told to allocate
> the string, the char* lpBuffer argument is expected to be a pointer
> to void*, i.e., void**, and the function does something like this:
>     *(void**)lpBuffer = LocalAlloc (..., nSize);
>     sprintf (*(char**)lpBuffer, "%s", message);
> There is no clean way for the caller to pass a void** to a function
> that takes a char*. Clearly a design flaw in the API but what else
> is new. We will have to live with the cast.
>> Also, the return value from LocalFree probably should be checked 
>> (There isn't much we can do if it fails, but we probably should warn 
>> the user that it failed, and provide him/her with the error number, 
>> but not a string translation to avoid entering a potentially infinite 
>> loop).
> Right. We should definitely check the return values of most calls
> and report errors or warnings. But trying to handle errors that
> occur while handling other errors is a catch 22, so I would skip
> this type of error checking and reporting in warn() or terminate()
> (although if FormatMessage fails we should still try to produce
> an error message without the formatted text).
>> The second observation is related to the final call to 
>> WaitForSingleObject and the new calls to CloseHandle.  For 
>> consistency, we should check the return value from each of these 
>> calls, and call warn_last_error if they failed (failure being defined 
>> as 0 for CloseHandle and and WAIT_FAILED for WaitForSingleObject).
> I agree. Can you post a patch?
> Martin

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