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SubjectRe: [PATCH] lib: test_scanf: Add explicit type cast to result initialization in test_number_prefix()
On Fri, Aug 04, 2023 at 07:25:00AM +0300, Andy Shevchenko wrote:
> On Thu, Aug 03, 2023 at 11:14:42AM -0700, Nathan Chancellor wrote:
> > A recent change in clang allows it to consider more expressions as
> > compile time constants, which causes it to point out an implicit
> > conversion in the scanf tests:
> >
> > lib/test_scanf.c:661:2: warning: implicit conversion from 'int' to 'unsigned char' changes value from -168 to 88 [-Wconstant-conversion]
> > 661 | test_number_prefix(unsigned char, "0xA7", "%2hhx%hhx", 0, 0xa7, 2, check_uchar);
> > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > lib/test_scanf.c:609:29: note: expanded from macro 'test_number_prefix'
> > 609 | T result[2] = {~expect[0], ~expect[1]}; \
> > | ~ ^~~~~~~~~~
> > 1 warning generated.
> >
> > The result of the bitwise negation is the type of the operand after
> > going through the integer promotion rules, so this truncation is
> > expected but harmless, as the initial values in the result array get
> > overwritten by _test() anyways. Add an explicit cast to the expected
> > type in test_number_prefix() to silence the warning. There is no
> > functional change, as all the tests still pass with GCC 13.1.0 and clang
> > 18.0.0.
>
> > do { \
> > const T expect[2] = { expect0, expect1 }; \
> > - T result[2] = {~expect[0], ~expect[1]}; \
> > + T result[2] = {(T)~expect[0], (T)~expect[1]}; \
>
> Can we add spaces as above, while at it?
>
> T result[2] = { (T)~expect[0], (T)~expect[1] }; \

Sure. I can send a v2 on Monday to give folks a chance to chime in with
other comments.

> > _test(fn, &expect, str, scan_fmt, n_args, &result[0], &result[1]); \
> > } while (0)
>
> --
> With Best Regards,
> Andy Shevchenko
>
>

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