Re: regression in tgamma?

[Paul Zimmermann <Paul.Zimmermann@inria.fr>]

       Hi Jeff,

thank you for your answer. Here are the steps I followed to compile Newlib
(thanks Alexei Sibidanov):

# from newlib-3.3.0 or newlib-4.0.0
mkdir build
cd build
../configure --prefix=`pwd` --target=x86_64
# perform the following in $HOME/bin
ln -sf `which ar` x86_64-ar
ln -sf `which as` x86_64-as
ln -sf `which cc` x86_64-cc
ln -sf `which gcc` x86_64-gcc
ln -sf `which c++` x86_64-c++
ln -sf `which ld` x86_64-ld
ln -sf `which nm` x86_64-nm
ln -sf `which objdump` x86_64-objdump
ln -sf `which objcopy` x86_64-objcopy
ln -sf `which ranlib` x86_64-ranlib
ln -sf `which readelf` x86_64-readelf
ln -sf `which strip` x86_64-strip
make # it will fail but it is ok
cd x86_64/newlib/libm
make # fails too
cd tmp
ar cr libm.a *.o

If you have access to the GCC Compile Farm [1], you can reproduce on gcc67:

$ cd /home/zimmerma
$ gcc -DNEWLIB -no-pie test3.c newlib-3.3.0/build/x86_64/newlib/libm/tmp/libm.a
$ ./a.out 
x=-0x1.53f198fe3b278p+7 y=0x1.fd6d312572d9cp-1015
$ gcc -DNEWLIB -no-pie test3.c newlib-4.0.0/build/x86_64/newlib/libm/tmp/libm.a
$ ./a.out 
x=-0x1.53f198fe3b278p+7 y=0x1p+0

If you have a simpler way to compile Newlib, please tell me.

Best regards,
Paul

[1] https://gcc.gnu.org/wiki/CompileFarm#List_of_machines

> From: Jeff Johnston <jjohnstn@redhat.com>
> Date: Tue, 15 Dec 2020 12:11:25 -0500
> 
> Hi Paul,
> 
> I copied the newlib/libm/common directory and header files from master to a
> separate directory and called __ieee754_tgamma directly in your test (adding
> a declaration of __ieee754_tgamma as well).  I then built as follows:
> 
> gcc -g -O0 -I. -DNEWLIB  testtgamma.c e_tgamma.c e_exp.c k_sin.c math_err.c
> er_lgamma.c k_cos.c s_floor.c e_log.c w_log.c
> 
> I get the same result as you get for 3.3.0. 
> 
> Can you possibly recheck to see if your 4.0.0 library has been built
> correctly?  Perhaps I have somehow by-passed the cause of the problem by
> compiling directly.
> 
> -- Jeff J.
> 
> On Tue, Dec 15, 2020 at 8:36 AM Paul Zimmermann <Paul.Zimmermann@inria.fr>
> wrote:
> 
>         Hi,
> 
>  while updating my comparison from Newlib 3.3.0 to Newlib 4.0.0, I found
>  a
>  regression in tgamma on x86_64/Linux:
> 
>  $ cat test3.c
>  #include <stdio.h>
>  #include <math.h>
> 
>  #ifdef NEWLIB
>  int errno;
>  int* __errno () { return &errno; }
>  #endif
> 
>  int main()
>  {
>    double x = -0x1.53f198fe3b278p+7, y;
>    y = tgamma (x);
>    printf ("x=%a y=%a\n", x, y);
>  }
> 
>  Newlib 3.3.0:
>  $ gcc -DNEWLIB -no-pie test3.c /localdisk/zimmerma/newlib-3.3.0/libm.a;
>  ./a.out
>  x=-0x1.53f198fe3b278p+7 y=0x1.fd6d312572d9cp-1015
> 
>  Newlib 4.0.0:
>  $ gcc -DNEWLIB -no-pie test3.c /localdisk/zimmerma/newlib-4.0.0/libm.a;
>  ./a.out
>  x=-0x1.53f198fe3b278p+7 y=0x1p+0
> 
>  Please can someone confirm?
> 
>  Best regards,
>  Paul