Bug 55906 – libnids fails while compiling (gcc 3.5) with -fPIC due to clobbered register

• Status: RESOLVED FIXED
• Product: Gentoo Linux

[Description Jon Oberheide 2004-07-02 12:30:00 UTC]

when emerging libnids-1.18 with gcc 3.5:

cd src ; make  shared
make[1]: Entering directory `/var/tmp/portage/libnids-1.18/work/libnids-1.18/src'
gcc -fPIC -march=athlon-xp -O3 -pipe -D_BSD_SOURCE -Wall -DLIBNET_VER=1 -DHAVE_ICMPHDR=1 -DHAVE_TCP_STATES=1 -DHAVE_BSD_UDPHDR=1 -I. -I/usr/include -I/usr/include -D_BSD_SOURCE -D__BSD_SOURCE -D__FAVOR_BSD -DHAVE_NET_ETHERNET_H -c checksum.c -o checksum_pic.o
checksum.c: In function `csum_partial':
checksum.c:25: error: PIC register `bx' clobbered in `asm'
make[1]: *** [checksum_pic.o] Error 1
make[1]: Leaving directory `/var/tmp/portage/libnids-1.18/work/libnids-1.18/src'
make: *** [shared] Error 2

bx is already in the clobbered register list.  I'm no expert on how GCC handles the clobbered registers but removing bx from the clobber list allows it to compile successfully.  Can anyone verify that this is the correct way to handle this?

Regards,
Jon Oberheide
[e-mail]

Reproducible: Always
Steps to Reproduce:

[Comment 1 Jon Oberheide 2004-07-02 12:31:51 UTC]

Created attachment 34667 [details, diff]
patch

[Comment 2 Itay Greenspon 2004-10-12 06:00:31 UTC]

Same thing happens here, using:
gcc (GCC) 3.4.2  (Gentoo Linux 3.4.2-r2, ssp-3.4.1-1, pie-8.7.6.5)

Error message is:
----------------------------------------------------START-------------------
gcc -fPIC -march=pentium4 -O3 -mtune=pentium4 -fomit-frame-pointer -pipe -D_BSD_SOURCE -Wall -DLIBNET_VER=1 -DHAVE_ICMPHDR=1 -DHAVE_TCP_STATES=1 -DHAVE_BSD_UDPHDR=1 -I. -I/usr/include -I/usr/include -D_BSD_SOURCE -D__BSD_SOURCE -D__FAVOR_BSD -DHAVE_NET_ETHERNET_H -c checksum.c -o checksum_pic.o
checksum.c: In function `csum_partial':
checksum.c:25: error: PIC register `bx' clobbered in `asm'
make[1]: *** [checksum_pic.o] Error 1
------------------------------------------------------END-------------------

[Comment 3 Thomas 2004-11-02 11:45:30 UTC]

Created attachment 43179 [details, diff]
src/checksum.c, save/restore ebx

IMO one should be more careful about EBX. I would prefer saving/restoring it
instead of removing the register from the clobber list. See the attached patch.

(can confirm the same problem with gcc-3.4.2)

[Comment 4 Josh Nichols (RETIRED) 2004-11-04 08:59:39 UTC]

Created attachment 43291 [details]
An ebuild which uses Thomas's libnids-1.18-chksum.c.diff

I can confirm that Thomas's libnids-1.18-chksum.c.diff fixes the problem. I've
attached an ebuild that makes uses of it.

[Comment 5 Dion Sole 2004-11-08 18:00:09 UTC]

I had this bug with gcc 3.4.2. 
The ebuild and patch compiled cleanly for me and fixed the issue

[Comment 6 Eldad Zack (RETIRED) 2004-12-17 04:22:26 UTC]

Thomas, thanks for the patch.
in portage.