Re: copy lfs build to older CPU

Hallo,
>>> dmesg should show exactly which file contains the offending instruction.
I still have the non-functioning LFS partition so I can do further 
experiments.
Still runs on the same error at compiling sff-common.c, still no dmesg 
output despite the sysctl change.
Checked with "sysctl -a | grep trace" - it's really set to 1.
Is there anything else to switch on to have dmesg output like yours?

Recompiling gmp-6.3.0 on i7, packing a .tar archive with these files:
# tar -tf /sources/gmp-6.3.0.tar
usr/
usr/lib/
usr/lib/libgmp.so.10
usr/lib/libgmpxx.la
usr/lib/pkgconfig/
usr/lib/pkgconfig/gmpxx.pc
usr/lib/pkgconfig/gmp.pc
usr/lib/libgmpxx.so.4
usr/lib/libgmp.so.10.5.0
usr/lib/libgmpxx.so
usr/lib/libgmpxx.so.4.7.0
usr/lib/libgmp.la
usr/lib/libgmp.so
usr/share/
usr/share/info/
usr/share/info/gmp.info
usr/share/info/gmp.info-1
usr/share/info/gmp.info-2
usr/share/info/dir
usr/include/
usr/include/gmp.h
usr/include/gmpxx.h

scp'ed to the i5 system, unpacked, still no luck.

Then recompiled libffi, and I noticed only at the 3rd glance that Fedora 
forces (yes, really hard) installation in /usr/lib64, even if I try to 
override it with --libdir=/usr/lib on the configure command line. I even 
changed the global "config.site" script where it forces lib64.
I'm rebooting the i5 machine so that I have a native LFS gcc compiler to 
rebuild gmp and libffi.
Funny that gmp is installed in the correct, intended location of 
/usr/lib, but libffi is stubbornly insisting on /usr/lib64.

After rebooting and recompiling gmp and libffi, copying to their places, 
rebooting to the defect build, still doesn't work :-(.
I had really high hopes for this latest try.

# tar tvf /libffi-3.5.2.tar
drwxr-xr-x root/root         0 2025-09-26 17:56 usr/
drwxr-xr-x root/root         0 2025-09-26 17:56 usr/share/
drwxr-xr-x root/root         0 2025-09-26 17:56 usr/share/info/
-rw-r--r-- root/root       631 2025-09-26 17:56 usr/share/info/dir
-rw-r--r-- root/root     40391 2025-09-26 17:56 usr/share/info/libffi.info
drwxr-xr-x root/root         0 2025-09-26 17:56 usr/share/man/
drwxr-xr-x root/root         0 2025-09-26 17:56 usr/share/man/man3/
-rw-r--r-- root/root      2333 2025-09-26 17:56 
usr/share/man/man3/ffi_call.3
-rw-r--r-- root/root       850 2025-09-26 17:56 usr/share/man/man3/ffi.3
-rw-r--r-- root/root      1321 2025-09-26 17:56 
usr/share/man/man3/ffi_prep_cif_var.3
-rw-r--r-- root/root      1158 2025-09-26 17:56 
usr/share/man/man3/ffi_prep_cif.3
drwxr-xr-x root/root         0 2025-09-26 17:56 usr/lib/
drwxr-xr-x root/root         0 2025-09-26 17:56 usr/lib/pkgconfig/
-rw-r--r-- root/root       256 2025-09-26 17:56 usr/lib/pkgconfig/libffi.pc
-rwxr-xr-x root/root     73720 2025-09-26 17:56 usr/lib/libffi.so.8.2.0
lrwxrwxrwx root/root         0 2025-09-26 17:56 usr/lib/libffi.so.8 -> 
libffi.so.8.2.0
lrwxrwxrwx root/root         0 2025-09-26 17:56 usr/lib/libffi.so -> 
libffi.so.8.2.0
-rwxr-xr-x root/root       903 2025-09-26 17:56 usr/lib/libffi.la
drwxr-xr-x root/root         0 2025-09-26 17:56 usr/include/
-rw-r--r-- root/root      4928 2025-09-26 17:56 usr/include/ffitarget.h
-rw-r--r-- root/root     14600 2025-09-26 17:56 usr/include/ffi.h

# cd /sources/ethtool-5.0/
root@lfs /sources/ethtool-5.0 # gcc -DHAVE_CONFIG_H -I. 
-I/usr/include/tirpc -Wall -g -O -c -o sff-common.o sff-common.c
sff-common.c: In function ‘convert_mw_to_dbm’:
sff-common.c:29:9: internal compiler error: Illegal instruction
    29 |         return (10. * log10(mw / 1000.)) + 30.;
       |         ^~~~~~

# sysctl -a |grep -- -trace
debug.exception-trace = 1

# dmesg | tail -5
[    2.397732] EXT4-fs (sda5): mounted filesystem 
bd9efb79-cb7e-4fa1-999e-e7723bf7b3bf r/w with ordered data mode. Quota 
mode: none.
[    2.718763] RTL8211E Gigabit Ethernet r8169-0-300:00: attached PHY 
driver (mii_bus:phy_addr=r8169-0-300:00, irq=MAC)
[    2.902460] ip (2260) used greatest stack depth: 11144 bytes left
[    2.903993] r8169 0000:03:00.0 enp3s0: Link is Down
[    5.691338] r8169 0000:03:00.0 enp3s0: Link is Up - 1Gbps/Full - flow 
control rx/tx


Thanks again +
Stay healthy,
Thomas
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