Re: vfprintf.c:(.text+0xc6c): undefined reference to `__signbitl'

[Szabolcs Nagy <nsz@port70.net>]

* meres5@alpha.tmit.bme.hu <meres5@alpha.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@alpha:/home/meres5/tmp# ld crt1.o stdhello.o -L. -lc -lgcc -o stdhello
> root@alpha:/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