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Date: Wed, 10 Apr 2013 00:38:06 +0200
From: Szabolcs Nagy <nsz@...t70.net>
To: musl@...ts.openwall.com
Subject: Re: vfprintf.c:(.text+0xc6c): undefined reference to
`__signbitl'
* meres5@...ha.tmit.bme.hu <meres5@...ha.tmit.bme.hu> [2013-04-09 22:15:40 +0200]:
> > this is bad, it is 'double-double' long double format
> > which means broken long double arithmetics
> >
>
> Its the out of the box debian, installed on our
> old IBM eServer pSeries 615 (7029 6C3).
> Surprisingly a native PPC host/target/and everything. . .
yes, double-double is also called the 128bit ibm format
and it used to be defined this way in the powerpc abi
(recently gcc changed to the 128bit ieee format if i
understood the libgcc code correctly)
> > (every trivial program will get an entire floating point
> > emulation library linked in from libgcc pulled in by printf
> > so the students will get the impression that static linking
> > always gives bloated binaries..)
>
> The picture is not that bad.
> Finally I managed to unleash the two functions in question
> in ~/src/musl-0.9.9/src/math: __signbitl and __fpclassifyl with some
> #if bombing and voilla!
>
> root@...ha:/home/meres5/tmp# ld crt1.o stdhello.o -L. -lc -lgcc -o stdhello
> root@...ha:/home/meres5/tmp# chroot . ./stdhello
> Hello
>
> worked and its 'only' 25k.
nice
> > linux did not drop it, but for some reason the glibc and
> > binutils maintainers thought that dynamic linking is always
> > better so it's enough to support that
> Yep.
> Finally I got it - thanks for the MUSL team!
>
> And the good news:
> - worked
> - I have checked several other libc for embedded, supporting static ld
> and only musl prevails with some really little hack in source.
> Others claimed broken tool-chain (by being surprised not in a
> cross compling toolchain)
i'm glad it worked
> Bad news:
> - Someone had better to have a look at those conditionals in
> __signbitl.c and __fpclassifyl.c
adding support for a new long double representation
is non-trivial
but you are right that code without floating-point
should work even on systems with weird long double
i will look into that later
meanwhile on powerpc gcc has -mlong-double-64 option
to compile with 64bit long doubles, maybe the musl
config script should check for that and add it when
the long double format is unsupported
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