Re: c/9762: Address of 'char' is incorrect.

Re: c/9762: Address of 'char' is incorrect.

[ebotcazou]

Synopsis: Address of 'char' is incorrect.

State-Changed-From-To: open->feedback
State-Changed-By: ebotcazou
State-Changed-When: Thu Feb 20 08:06:46 2003
State-Changed-Why:
    Neil's question.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=9762

Re: c/9762: Address of 'char' is incorrect.

[neil]

Synopsis: Address of 'char' is incorrect.

State-Changed-From-To: feedback->closed
State-Changed-By: neil
State-Changed-When: Thu Feb 20 20:33:30 2003
State-Changed-Why:
    Not a bug, just not what user expected.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=9762

Re: c/9762: Address of 'char' is incorrect.

[Daniel Jacobowitz]

The following reply was made to PR c/9762; it has been noted by GNATS.

From: Daniel Jacobowitz <dan@debian.org>
To: Stephen Kennedy <Stephen.Kennedy@havok.com>
Cc: 'Neil Booth' <neil@daikokuya.co.uk>, gcc-gnats@gcc.gnu.org,
	debian-gcc@lists.debian.org
Subject: Re: c/9762: Address of 'char' is incorrect.
Date: Thu, 20 Feb 2003 14:03:30 -0500

 On Thu, Feb 20, 2003 at 06:32:19PM -0000, Stephen Kennedy wrote:
 > 
 > OK, the C standard does not say that this should work, so you
 > can consider this bug closed.
 > 
 > However, given knowledge of the calling convention of a
 > particular machine, you can do neat things such as dynamic
 > function binding. See www.drizzle.com/~scottb/gdc/fubi-paper.htm
 > for instance.
 > 
 > I've since changed to using assembly, but why does gcc
 > return the address of a temp when 'a' is a char and not
 > when 'a' is an int?
 
 Because it's passed as an int; you have to convert it to a char on
 arrival in the function.
 
 > 
 > Surprised, not unhappy,
 > Stephen.
 > 
 > ---
 > Stephen Kennedy <Stephen.Kennedy@havok.com>
 > t: +353 1 6693679   f: +353 1 6767094
 > Game Developer Frontline Award Winner
 > http://www.havok.com/news/release.html
 > 
 > > > 	In the example below, '&a' is the address of a local 
 > > copy of 'a' not of 'a'.
 > > > 	if the type of 'a' is changed to int, it works as expected.
 > > 
 > > Works as who expected?  Where is the bug?  Please quote which part of
 > > the C standard is violated.  You got an address, why are you unhappy?
 > > 
 > > Neil.
 > > 
 > > > #define TA char
 > > > #define TB int
 > > > #define TC int
 > > > 
 > > > void foobar(TA a, TB b, TC c);
 > > > 
 > > > int main()
 > > > {
 > > > 	foobar(1,2,3);
 > > > 	return 0;
 > > > }
 > > > 
 > > > void foobar(TA a, TB b, TC c)
 > > > {
 > > > 	printf("a == %i  claims %x\n", a, &a);
 > > > 	printf("a == %i  really %x\n", (&b)[-1], (&b)-1);
 > > > 	printf("b == %i  %x\n", b, &b);
 > > > 	printf("c == %i  %x\n", c, &c);
 > > > }
 > > 
 > 
 > 
 > -- 
 > To UNSUBSCRIBE, email to debian-gcc-request@lists.debian.org
 > with a subject of "unsubscribe". Trouble? Contact listmaster@lists.debian.org
 > 
 > 
 
 -- 
 Daniel Jacobowitz
 MontaVista Software                         Debian GNU/Linux Developer

RE: c/9762: Address of 'char' is incorrect.

[Stephen Kennedy]

The following reply was made to PR c/9762; it has been noted by GNATS.

From: "Stephen Kennedy" <Stephen.Kennedy@havok.com>
To: "'Neil Booth'" <neil@daikokuya.co.uk>
Cc: <gcc-gnats@gcc.gnu.org>,
	<debian-gcc@lists.debian.org>
Subject: RE: c/9762: Address of 'char' is incorrect.
Date: Thu, 20 Feb 2003 18:32:19 -0000

 OK, the C standard does not say that this should work, so you
 can consider this bug closed.
 
 However, given knowledge of the calling convention of a
 particular machine, you can do neat things such as dynamic
 function binding. See www.drizzle.com/~scottb/gdc/fubi-paper.htm
 for instance.
 
 I've since changed to using assembly, but why does gcc
 return the address of a temp when 'a' is a char and not
 when 'a' is an int?
 
 Surprised, not unhappy,
 Stephen.
 
 ---
 Stephen Kennedy <Stephen.Kennedy@havok.com>
 t: +353 1 6693679   f: +353 1 6767094
 Game Developer Frontline Award Winner
 http://www.havok.com/news/release.html
 
 > > 	In the example below, '&a' is the address of a local 
 > copy of 'a' not of 'a'.
 > > 	if the type of 'a' is changed to int, it works as expected.
 > 
 > Works as who expected?  Where is the bug?  Please quote which part of
 > the C standard is violated.  You got an address, why are you unhappy?
 > 
 > Neil.
 > 
 > > #define TA char
 > > #define TB int
 > > #define TC int
 > > 
 > > void foobar(TA a, TB b, TC c);
 > > 
 > > int main()
 > > {
 > > 	foobar(1,2,3);
 > > 	return 0;
 > > }
 > > 
 > > void foobar(TA a, TB b, TC c)
 > > {
 > > 	printf("a == %i  claims %x\n", a, &a);
 > > 	printf("a == %i  really %x\n", (&b)[-1], (&b)-1);
 > > 	printf("b == %i  %x\n", b, &b);
 > > 	printf("c == %i  %x\n", c, &c);
 > > }
 > 

Re: c/9762: Address of 'char' is incorrect.

[Andreas Schwab]

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The following reply was made to PR c/9762; it has been noted by GNATS.

From: Andreas Schwab <schwab@suse.de>
To: stephen.kennedy@havok.com
Cc: gcc-gnats@gcc.gnu.org, debian-gcc@lists.debian.org
Subject: Re: c/9762: Address of 'char' is incorrect.
Date: Thu, 20 Feb 2003 15:26:33 +0100

 stephen.kennedy@havok.com writes:
 
 |> #define TA char
 |> #define TB int
 |> #define TC int
 |> 
 |> void foobar(TA a, TB b, TC c);
 |> 
 |> int main()
 |> {
 |> 	foobar(1,2,3);
 |> 	return 0;
 |> }
 |> 
 |> void foobar(TA a, TB b, TC c)
 |> {
 |> 	printf("a == %i  claims %x\n", a, &a);
 |> 	printf("a == %i  really %x\n", (&b)[-1], (&b)-1);
 
 There is nothing in the C standard that requires that (char*)(&b-1) == &a.
 They are distinct objects, thus not comparable, and &b-1 by itself is
 already invalid.
 
 Andreas.
 
 -- 
 Andreas Schwab, SuSE Labs, schwab@suse.de
 SuSE Linux AG, Deutschherrnstr. 15-19, D-90429 Nürnberg
 Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
 "And now for something completely different."

Re: c/9762: Address of 'char' is incorrect.

[Neil Booth]

The following reply was made to PR c/9762; it has been noted by GNATS.

From: Neil Booth <neil@daikokuya.co.uk>
To: stephen.kennedy@havok.com
Cc: gcc-gnats@gcc.gnu.org, debian-gcc@lists.debian.org
Subject: Re: c/9762: Address of 'char' is incorrect.
Date: Wed, 19 Feb 2003 21:23:55 +0000

 stephen.kennedy@havok.com wrote:-
 
 > 	In the example below, '&a' is the address of a local copy of 'a' not of 'a'.
 > 	if the type of 'a' is changed to int, it works as expected.
 
 Works as who expected?  Where is the bug?  Please quote which part of
 the C standard is violated.  You got an address, why are you unhappy?
 
 Neil.
 
 > #define TA char
 > #define TB int
 > #define TC int
 > 
 > void foobar(TA a, TB b, TC c);
 > 
 > int main()
 > {
 > 	foobar(1,2,3);
 > 	return 0;
 > }
 > 
 > void foobar(TA a, TB b, TC c)
 > {
 > 	printf("a == %i  claims %x\n", a, &a);
 > 	printf("a == %i  really %x\n", (&b)[-1], (&b)-1);
 > 	printf("b == %i  %x\n", b, &b);
 > 	printf("c == %i  %x\n", c, &c);
 > }

c/9762: Address of 'char' is incorrect.

[stephen.kennedy]

>Number:         9762
>Category:       c
>Synopsis:       Address of 'char' is incorrect.
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          wrong-code
>Submitter-Id:   net
>Arrival-Date:   Wed Feb 19 19:56:01 UTC 2003
>Closed-Date:
>Last-Modified:
>Originator:     Stephen Kennedy
>Release:        3.2.3 20030210 (Debian prerelease) (Debian testing/unstable)
>Organization:
Telekinesys Research
>Environment:
System: Linux stag 2.4.19-686 #1 Thu Aug 8 21:30:09 EST 2002 i686 unknown
Architecture: i686

	
host: i386-pc-linux-gnu
build: i386-pc-linux-gnu
target: i386-pc-linux-gnu
configured with: ../src/configure -v --enable-languages=c,c++,java,f77,proto,pascal,objc,ada --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --with-gxx-include-dir=/usr/include/c++/3.2 --enable-shared --with-system-zlib --enable-nls --without-included-gettext --enable-__cxa_atexit --enable-clocale=gnu --enable-java-gc=boehm --enable-objc-gc i386-linux
>Description:

	In the example below, '&a' is the address of a local copy of 'a' not of 'a'.
	if the type of 'a' is changed to int, it works as expected.

>How-To-Repeat:

#define TA char
#define TB int
#define TC int

void foobar(TA a, TB b, TC c);

int main()
{
	foobar(1,2,3);
	return 0;
}

void foobar(TA a, TB b, TC c)
{
	printf("a == %i  claims %x\n", a, &a);
	printf("a == %i  really %x\n", (&b)[-1], (&b)-1);
	printf("b == %i  %x\n", b, &b);
	printf("c == %i  %x\n", c, &c);
}

>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted: