US-CERT Vulnerability Note VU#162289

[Robert Dewar]

Joe Buck wrote:
> On Mon, Apr 14, 2008 at 06:42:30PM -0400, Robert Dewar wrote:
>>> [In fact,
>>> after GCC does something to warn users about this, it'll be
>>> much "safer" than those other compilers.]
>> For sure you want a warning, the compiler should never be
>> removing explicit tests in the users code without generating
>> a warning I would think.
> 
> I vaguely recall a paper from Dawson Engler's group (the people who
> did the Stanford Checker and Coverity) about warnings for dead code
> removal.  They are often bugs if seen in straight-line code, but
> macros as well as inlining of functions will produce many warnings
> of this kind.  They focused their work on addressing what the user
> could be expected to know, the idea being to issue warnings if
> the code on a single level is redundant, but suppress warnings
> if the redundant text came from macros or inlining.

Right, we have heuristics in the Ada front end along these lines.
For instance, you generally want to be warned if a test is
always true or always false, but if the test is

    if XYZ then

where XYZ is a boolean constant, then probably this is
conditional compilation type activity that is legitimate.