[cfe-dev] Why does scan-build disable check for uninit values?

[Ted Kremenek]

On Jan 3, 2009, at 1:43 AM, Cristian Draghici wrote:

>
>
> On Sat, Jan 3, 2009 at 11:09 AM, Cristian Draghici <cristian.draghici at gmail.com 
> > wrote:
>
>
> On Fri, Jan 2, 2009 at 11:43 PM, Ted Kremenek <kremenek at apple.com>  
> wrote:
>
> On Jan 2, 2009, at 2:18 AM, Cristian Draghici wrote:
>
> Hi
>
> I've noticed that scan-build in the latest version of the checker  
> (137) disables the check for uninit values (-warn-uninit-values).
> Is there a reason behind that?
>
>
> Thank you,
> Cristi
>
> In the static analyzer, checking for uninitialized values, just as  
> with checking for null dereferences, is done as part of the core  
> path-sensitive logic used for -checker-cfref and -checker-simple.   
> It isn't controlled by -warn-uninit-values.
>
> The -warn-uninit-values option performs a fast check for uses of  
> uninitialized values that is similar to GCC's -Wuninitialized.  It  
> should be thought of as a cheap check that can be used (one day) as  
> a compiler warning rather than a deep check done by the static  
> analyzer.  The checking for uninitialized values done by the static  
> analyzer is far more precise.
>
> Some of these options should probably be renamed to avoid such  
> confusion.
>
> My confusion was actually caused by the different output of "- 
> checker-cfref" vs "-warn-uninit-values".
>
> In the warning below shouldn't clang say "Pass-by-value argument in  
> function is uninitialized"?
> English is not my native language so I may be wrong but I tend to  
> equate "undefined" with "undeclared" (as in lacking definition).
>
> diciu$ ~/Downloads/checker-137/clang -x c test.c   -checker-cfref
> ANALYZE: test.c main
> test.c:6:2: warning: Pass-by-value argument in function is undefined.
>         strcpy(t, g);
>         ^      ~
> 1 diagnostic generated.
>
>
> diciu$ ~/Downloads/checker-137/clang -x c test.c   -warn-uninit-values
> test.c:6:9: warning: use of uninitialized variable
>         strcpy(t, g);
>                ^
> test.c:6:12: warning: use of uninitialized variable
>         strcpy(t, g);
>                   ^
> 2 diagnostics generated.
>
> test.c is:
>
> #include <string.h>
>
> int main()
> {
> 	char * t, * g;
> 	strcpy(t, g);
>
> 	return 0;
> }
>
>
>
>
> Oh, nevermind, I get it.
>
> "Pass-by-value argument in function is undefined" probably refers to  
> the value pointed to by the char pointer as being undefined, which  
> it is.

That's it.  I used the terminology "undefined" because undefined  
values can come from other sources other than uninitialized  
variables.  The warning, however, could probably be worded a little  
more clearly.

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