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Date: Thu, 3 Sep 2020 20:34:42 +0800
From: Ruinland ChuanTzu Tsai <ruinland@andestech.com>
To: <libc-alpha@sourceware.org>
CC: <tesheng@andestech.com>
Subject: In libm, sin(qNaN) doesn't expect FE_INVALID ?
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Hi all,
sorry for the bothering.

Recently, as I'm testing some modification on libm, I happen to realize
the fact that glibc's testsutie doesn't expect sin(+-qNaN) to trigger
FE_INVALID, which is designed in `math/libm-test-sin.inc` :

TEST_f_f (sin, qnan_value, qnan_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED)
TEST_f_f (sin, -qnan_value, qnan_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED)

Yet I think that if the program issued sin(qNaN), it should be okay to
be given an invalid operation excpetion. 

If that's the case, then appending `INVALID_EXCEPTION_OK` to the
expected exception list of sin(qNaN) and sin(-qNaN) should be benign.

Though I'm neither an expert on libm nor IEEE standards, I'm wondering
will there be any concern of such behavior ( raising FE_INVALID on
sin(+-qNaN) ) ?

Sincerely,
Ruinland