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Re: [PATCHv2] sysdeps/ieee754: prevent maybe-uninitialized errors [BZ #19444]
On Sat, 29 Sep 2018, Martin Jansa wrote:
> +/* With GCC 8 when compiling with -O the compiler
> + warns that the variable 'temp', may be used uninitialized.
> + The switch above should cover all possible values of n & 3
> + so I belive it's false possitive. */
> +DIAG_IGNORE_NEEDS_COMMENT (8, "-Wmaybe-uninitialized");
> b = invsqrtpi * temp / sqrtl (x);
DIAG_* and associated comments should be indented to match the associated
code rather than at the left margin. Any alphabetic characters at the
left margin in the middle of a function are a bad idea because they break
things trying to determine the function name for diff context etc.
As per <https://sourceware.org/ml/libc-alpha/2018-09/msg00311.html> I
think it would be best to add DIAG_IGNORE_O1_NEEDS_COMMENT to libc-diag.h,
and use it for cases such as here that only need the diagnostics disabled
glibc code is written and maintained by many people over time, so there
shouldn't be an "I" in comments; they should reflect a current collective
understanding rather than one person's view, and read as such. Also, the
point isn't that the switch *should* cover all possible value of n & 3,
it's that it *does* cover all possible values (and sets temp in every
case) and so the warning *is* a false positive.
Joseph S. Myers