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Re: Test tstdiomisc fails when multiplication of NAN by -1 results in NAN
On Mon, May 24, 2010 at 12:09 PM, John David Anglin
<dave@hiauly1.hia.nrc.ca> wrote:
> On Mon, 24 May 2010, Carlos O'Donell wrote:
>
>> On Sun, May 23, 2010 at 12:37 PM, John David Anglin
>> <dave@hiauly1.hia.nrc.ca> wrote:
>> > Carlos,
>> >
>> > You have found a bug. ?The code should xor the sign bit when doing
>> > negation. ?The existing code doesn't work for NANs. ?I'll try to
>> > fix negdf2 and negsf2.
>>
>> Should I file a bug?
>
> I'm testing a fix. ?I'll install to 4.6 and backport later.
> A bug report would provide a record of the problem and fix.
Filed:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44261
>> You are correct, I've checked for 64-bit, and this is correct. I was
>> accidentally using the 32-bit float formats.
>>
>> However, there is a bug in gdb then, which shows the NaN value as a
>> 32-bit value and interprets only the top 32-bits of the 64-bit double
>> -1.0 and displays -1.875 as if it were a 32-bit float.
>
> Yah, I have never liked gdb's handling of floating point values.
> For example, does "p/x val" interpret `val' as a float or double
> when val is a hex constant string. ?It seems to depend on the
> length of the string. ?You can't specify a size with `p'. ?Values
> in registers are another story.
We'll fix this later... which I expect is exactly what I say every
time I come across this bug :-)
Cheers,
Carlos.