Re: [PATCH] xdiff/xdiffi.c: fix warnings about possibly uninitialized variables

On Sat, 8 Apr 2006, Marco Roeland wrote:

> Compiling this module gave the following warnings (some double dutch!):
>
> xdiff/xdiffi.c: In functie 'xdl_recs_cmp':
> xdiff/xdiffi.c:298: let op: 'spl.i1' may be used uninitialized in this function
> xdiff/xdiffi.c:298: let op: 'spl.i2' may be used uninitialized in this function
> xdiff/xdiffi.c:219: let op: 'fbest1' may be used uninitialized in this function
> xdiff/xdiffi.c:219: let op: 'bbest1' may be used uninitialized in this function
>
> A superficial tracking of their usage, without deeper knowledge about the
> algorithm, indeed confirms that there are code paths on which these
> variables will be used uninitialized. In practice these code paths might never
> be reached, but then these fixes will not change the algorithm. If these
> code paths are ever reached we now at least have a predictable outcome. And
> should the very small performance impact of these initializations be
> noticeable, then they should at least be replaced by comments why certain
> code paths will never be reached.

These paths are never reached because of the way data is prepared before 
and passed to the function. Unfortunately the compiler cannot know this.
Using them as -1 or XDL_LINE_MAX won't help either, since those are out of 
domain values. You can leave it there and the algo won't suffer, or you 
can relax a little the warning level when building the file.



- Davide


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