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From: Michael Marks <Michael.Marks@internetmachines.com>
To: nobody@gcc.gnu.org
Cc: gcc-prs@gcc.gnu.org,
Subject: RE: c/10226: unsigned short promotion with bitwise inversion
Date: Wed, 26 Mar 2003 19:56:00 -0000 [thread overview]
Message-ID: <20030326193602.7721.qmail@sources.redhat.com> (raw)
The following reply was made to PR c/10226; it has been noted by GNATS.
From: Michael Marks <Michael.Marks@internetmachines.com>
To: 'Falk Hueffner' <falk.hueffner@student.uni-tuebingen.de>
Cc: gcc-gnats@gcc.gnu.org
Subject: RE: c/10226: unsigned short promotion with bitwise inversion
Date: Wed, 26 Mar 2003 11:27:06 -0800
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Actually I understood that the warning was tied to that error.
I would suggest:
warning : ~ operator caused promotion of unsigned short to int
Interestingly: Sun CC passes and Microsoft Fails without warning.
Michael.
-----Original Message-----
From: Falk Hueffner [mailto:falk.hueffner@student.uni-tuebingen.de]
Sent: Wednesday, March 26, 2003 10:23 AM
To: mmarks@internetmachines.com
Cc: gcc-gnats@gcc.gnu.org
Subject: Re: c/10226: unsigned short promotion with bitwise inversion
mmarks@internetmachines.com writes:
> When two unsigned shorts (16 bit) variables are compared with one being
inverted the comparison will fail.
> The following code should pass, while it does generate a warning it
> should instead just work.
>
> unsigned short A = 0xDEAD;
> unsigned short B;
> B = ~A;
> if ( B == ~A) {
> printf("Pass\n");
> }
> else {
> printf("Fail\n");
> }
Apparently, you didn't understand the warning. The C standard mandates
that "~A" will promote A to int first. So gcc is behaving correctly
here. Any suggestions on how the wording of the message could be
improved to be clearer?
--
Falk
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<TITLE>RE: c/10226: unsigned short promotion with bitwise =
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<P><FONT SIZE=3D2>Actually I understood that the warning was tied to =
that error.</FONT>
</P>
<P><FONT SIZE=3D2>I would suggest:</FONT>
<BR><FONT SIZE=3D2>warning : ~ operator caused promotion of unsigned =
short to int</FONT>
</P>
<P><FONT SIZE=3D2>Interestingly: Sun CC passes and Microsoft Fails =
without warning.</FONT>
</P>
<P><FONT SIZE=3D2>Michael.</FONT>
</P>
<P><FONT SIZE=3D2>-----Original Message-----</FONT>
<BR><FONT SIZE=3D2>From: Falk Hueffner [<A =
HREF=3D"mailto:falk.hueffner@student.uni-tuebingen.de">mailto:falk.hueff=
ner@student.uni-tuebingen.de</A>]</FONT>
<BR><FONT SIZE=3D2>Sent: Wednesday, March 26, 2003 10:23 AM</FONT>
<BR><FONT SIZE=3D2>To: mmarks@internetmachines.com</FONT>
<BR><FONT SIZE=3D2>Cc: gcc-gnats@gcc.gnu.org</FONT>
<BR><FONT SIZE=3D2>Subject: Re: c/10226: unsigned short promotion with =
bitwise inversion</FONT>
</P>
<BR>
<P><FONT SIZE=3D2>mmarks@internetmachines.com writes:</FONT>
</P>
<P><FONT SIZE=3D2>> When two unsigned shorts (16 bit) variables are =
compared with one being inverted the comparison will fail.</FONT>
<BR><FONT SIZE=3D2>> The following code should pass, while it does =
generate a warning it</FONT>
<BR><FONT SIZE=3D2>> should instead just work.</FONT>
<BR><FONT SIZE=3D2>> </FONT>
<BR><FONT SIZE=3D2>> unsigned short A =3D =
0xDEAD;</FONT>
<BR><FONT SIZE=3D2>> unsigned short B;</FONT>
<BR><FONT SIZE=3D2>> B =3D ~A;</FONT>
<BR><FONT SIZE=3D2>> if ( B =3D=3D ~A) {</FONT>
<BR><FONT SIZE=3D2>> =
printf("Pass\n");</FONT>
<BR><FONT SIZE=3D2>> }</FONT>
<BR><FONT SIZE=3D2>> else {</FONT>
<BR><FONT SIZE=3D2>> =
printf("Fail\n");</FONT>
<BR><FONT SIZE=3D2>> }</FONT>
</P>
<P><FONT SIZE=3D2>Apparently, you didn't understand the warning. The C =
standard mandates</FONT>
<BR><FONT SIZE=3D2>that "~A" will promote A to int first. So =
gcc is behaving correctly</FONT>
<BR><FONT SIZE=3D2>here. Any suggestions on how the wording of the =
message could be</FONT>
<BR><FONT SIZE=3D2>improved to be clearer?</FONT>
</P>
<P><FONT SIZE=3D2>-- </FONT>
<BR> <FONT =
SIZE=3D2>Falk</FONT>
</P>
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next reply other threads:[~2003-03-26 19:36 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-03-26 19:56 Michael Marks [this message]
-- strict thread matches above, loose matches on Subject: below --
2003-03-27 0:16 Michael Marks
2003-03-26 23:06 Falk Hueffner
2003-03-26 22:36 Glen Nakamura
2003-03-26 22:26 Glen Nakamura
2003-03-26 22:26 Falk Hueffner
2003-03-26 22:06 Michael Marks
2003-03-26 21:56 Glen Nakamura
2003-03-26 21:56 Falk Hueffner
2003-03-26 21:16 ebotcazou
2003-03-26 21:16 Michael Marks
2003-03-26 20:36 Glen Nakamura
2003-03-26 18:26 Falk Hueffner
2003-03-26 18:16 mmarks
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