[ros-dev] Re: [ros-diffs] [weiden] 16536: return the length of the string excluding the null-termination character on success in GetEnvironmentVariable(). Thanks to Hartmut.

[Joseph Galbraith]

It seems like there is some uncertainty between this
code and RtlQueryEnvironmentVariable_U about who is
going to ensure that the string returned from
GetEnvironmentVariable() is nul terminated...

If I read the code in RtlQueryEnvironmentVariable_U
correctly (and I don't swear I have), it is possible
for it to return STATUS_SUCCESS and not copy a
NUL terminator.  This happens if the buffer is large
enough to contain the value but not the NUL terminator.

This is probably correct for this function since
UNICODE_STRINGs (and the Rtl* library) generally have
no requirement of a NUL terminator.

But then, if I read the code in GetEnvironmentVariable()
correctly, I don't believe it takes this situation into
account.

Probably, it would be best if RtlQueryEnvironmentVariable_U
_never_ copied the NUL terminator, and the caller was
always responsible for adding NUL termination, if needed.

Thanks,

Joseph

PS. MSDN is slightly unclear (to me) on how it should behave
in this case, but it seems unlikely that the real
GetEnvironmentVariable() returns success and a non-nul-terminated
string.  But I haven't written a test program to prove it.


weiden(a)svn.reactos.com wrote:
>   return the length of the string excluding the
> null-termination character on success in GetEnvironmentVariable(). Thanks to Hartmut.
>  
>  Modified: trunk/reactos/lib/kernel32/misc/env.c
>  
>  ------------------------------------------------------------------------
>  *Modified: trunk/reactos/lib/kernel32/misc/env.c*
>  
>  --- trunk/reactos/lib/kernel32/misc/env.c	2005-07-11 18:22:53 UTC (rev 16535)
>  +++ trunk/reactos/lib/kernel32/misc/env.c	2005-07-11 20:30:33 UTC (rev 16536)
>  @@ -91,7 +91,7 @@
>  
>   	/* free unicode variable name string */
>   	RtlFreeUnicodeString (&VarNameU);
>   
>  
>  -	return (VarValueU.Length / sizeof(WCHAR) + 1);
>  
>  +	return (VarValueU.Length / sizeof(WCHAR));
>  
>   }
>   
>   
>  @@ -133,7 +133,7 @@
>  
>   		}
>   	}
>   
>  
>  -	return (VarValue.Length / sizeof(WCHAR) + 1);
>  
>  +	return (VarValue.Length / sizeof(WCHAR));
>  
>   }
>   
>   
>