RPM's -fsigned-char (Re: [COMMITTERS] pgsql/src/backend/utils/adt (cash.c))

Thomas Lockhart <lockhart(at)alumni(dot)caltech(dot)edu> writes:
>> as for the behavior of Linux distribution vendors who set RPM_OPT_FLAGS
>> differently from the way they built libc, well, words fail me...

> Which distros would these be? I know that Mandrake chooses some mutually
> exclusive flags (-On and -fast-math) but am not sure which other ones
> are inconsistant...

The particular problem I was having was with LinuxPPC 2000. gcc's
default behavior on PPC is -funsigned-char, and that seems to be the
way that libc was built in that distro. But /usr/lib/rpm/rpmrc sets
RPM_OPT_FLAGS to "-fsigned-char -O2". (The -O2 wreaks havoc with
Postgres too, pre-fmgr-rewrite, but at least we knew about that effect.)

On closer examination, I think the blame lies with the RPM people and
not with LinuxPPC per se, because /usr/lib/rpm/rpmrc comes straight
from the RPM distro. Seems to me that libc *should* be built with
the default char-signedness for the platform, because otherwise programs
built outside the RPM environment will be broken. When RPM attempts to
force a non-default signedness for programs built in the RPM
environment, the only possible consequence is that someone or other gets
broken --- either RPM-based programs or non-RPM-based-programs, take
your pick. Ergo, it's RPM that's broken.

That same file has a bunch of apparently non-default compiler options
for other platforms besides PPC (for your amusement, I attach the
relevant lines from rpm-3.0.5 below). I wonder how many of those are
equally misguided...

regards, tom lane

# Values for RPM_OPT_FLAGS for various platforms

optflags: i386 -O2 -m486 -fno-strength-reduce
optflags: i486 -O2 -march=i486
optflags: i586 -O2 -march=i586
optflags: i686 -O2 -march=i686
optflags: athlon -O2 -march=athlon
optflags: ia64 -O2

# XXX Please note that -mieee has been added in rpm-3.0.5.
optflags: alpha -O2 -mieee

optflags: sparc -O2 -m32 -mtune=ultrasparc
optflags: sparcv9 -O2 -m32 -mcpu=ultrasparc
optflags: sparc64 -O2 -m64 -mcpu=ultrasparc
optflags: m68k -O2 -fomit-frame-pointer
optflags: ppc -O2 -fsigned-char
optflags: parisc -O2 -mpa-risc-1-0
optflags: hppa1.0 -O2 -mpa-risc-1-0
optflags: hppa1.1 -O2 -mpa-risc-1-0
optflags: hppa1.2 -O2 -mpa-risc-1-0
optflags: hppa2.0 -O2 -mpa-risc-1-0
optflags: mipseb -O2
optflags: mipsel -O2
optflags: armv4b -O2 -fsigned-char -fomit-frame-pointer
optflags: armv4l -O2 -fsigned-char -fomit-frame-pointer
optflags: atarist -O2 -fomit-frame-pointer
optflags: atariste -O2 -fomit-frame-pointer
optflags: ataritt -O2 -fomit-frame-pointer
optflags: falcon -O2 -fomit-frame-pointer
optflags: atariclone -O2 -fomit-frame-pointer
optflags: milan -O2 -fomit-frame-pointer
optflags: hades -O2 -fomit-frame-pointer