Hi Richard,
I get:
$ cat a.c
#include <stdlib.h>
int f(unsigned x, unsigned y) { return abs(x - y); }
$ ./clang -fsyntax-only a.c
a.c:2:40: warning: taking the absolute value of unsigned type
'unsigned int' has no effect [-Wabsolute-value]
int f(unsigned x, unsigned y) { return abs(x - y); }
[...]
Is it really right that the call to abs "has no effect"? Surely it
does have an effect: the unsigned value x-y is converted to int, and
if that value is negative then abs() will negate it.
Or have I misunderstood C?
Thanks,
Jay.
On 20 November 2013 02:08, Richard Trieu <[email protected]> wrote:
> This is a new warning to detect improper uses of the absolute value function.
> Three new warnings are introduced with this patch.
>
> 1) Attempting to take the absolute value of an unsigned integer. Includes
> fix-it to remove the absolute value function call.
> 2) Using an absolute value function that is too small. For instance, using
> abs(int) on a long would give a warning and a fix-it to use labs.
> 3) Using the wrong type of absolute value (integer, floating point, complex)
> for the argument given. Includes a fix-it to the proper absolute value type.
>
> I have already run this over a large code base and found hundreds of
> questionable usages of absolute value.
>
> http://llvm-reviews.chandlerc.com/D2224
>
> Files:
> test/Sema/warn-absolute-value.c
> include/clang/Basic/DiagnosticSemaKinds.td
> include/clang/Basic/DiagnosticGroups.td
> include/clang/Sema/Sema.h
> include/clang/AST/Decl.h
> lib/Sema/SemaChecking.cpp
> lib/AST/Decl.cpp
>
> _______________________________________________
> cfe-commits mailing list
> [email protected]
> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
>
_______________________________________________
cfe-commits mailing list
[email protected]
http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
