See also PR 47648 (same issue for FreeBSD on ia64; contrary to NetBSD/this PR it works on x86-64).

For FreeBSD/ia64 the problem is that _U_Q* are missing, though it is unclear whether NetBSD's libc or GCC's libgcc should provide those.
Cf. also bug 47649 comment 5.

--disable-libquadmath-support was enough to build.

However gfortran test results are pretty poor:

                === gfortran Summary ===

# of expected passes            24669
# of unexpected failures        11625
# of expected failures          41
# of unresolved testcases       40
# of unsupported tests          622


Lots of failures seems to be excess warning for cabsf() and cabs():

Executing on host: /home/guerby/build/gcc/testsuite/gfortran1/../../gfortran -B/home/guerby/build/gcc/testsuite/gfortran1/../../ -B/home/guerby/build/x86_64-unknown-netbsd5.1/./libgfortran/ /home/guerby/trunk/gcc/testsuite/gfortran.dg
/achar_1.f90   -O3 -g   -pedantic-errors  -B/home/guerby/build/x86_64-unknown-netbsd5.1/./libgfortran/.libs -L/home/guerby/build/x86_64-unknown-netbsd5.1/./libgfortran/.libs -L/home/guerby/build/x86_64-unknown-netbsd5.1/./libgfortran/
.libs  -lm   -o ./achar_1.exe    (timeout = 300)
spawn /home/guerby/build/gcc/testsuite/gfortran1/../../gfortran -B/home/guerby/build/gcc/testsuite/gfortran1/../../ -B/home/guerby/build/x86_64-unknown-netbsd5.1/./libgfortran/ /home/guerby/trunk/gcc/testsuite/gfortran.dg/achar_1.f90 
-O3 -g -pedantic-errors -B/home/guerby/build/x86_64-unknown-netbsd5.1/./libgfortran/.libs -L/home/guerby/build/x86_64-unknown-netbsd5.1/./libgfortran/.libs -L/home/guerby/build/x86_64-unknown-netbsd5.1/./libgfortran/.libs -lm -o ./ach
ar_1.exe
/home/guerby/build/x86_64-unknown-netbsd5.1/./libgfortran/.libs/libgfortran.so: warning: warning: reference to compatibility cabsf()
/home/guerby/build/x86_64-unknown-netbsd5.1/./libgfortran/.libs/libgfortran.so: warning: warning: reference to compatibility cabs()
output is:
/home/guerby/build/x86_64-unknown-netbsd5.1/./libgfortran/.libs/libgfortran.so: warning: warning: reference to compatibility cabsf()
/home/guerby/build/x86_64-unknown-netbsd5.1/./libgfortran/.libs/libgfortran.so: warning: warning: reference to compatibility cabs()

FAIL: gfortran.dg/achar_1.f90  -O3 -g  (test for excess errors)
Excess errors:
/home/guerby/build/x86_64-unknown-netbsd5.1/./libgfortran/.libs/libgfortran.so: warning: warning: reference to compatibility cabsf()
/home/guerby/build/x86_64-unknown-netbsd5.1/./libgfortran/.libs/libgfortran.so: warning: warning: reference to compatibility cabs()

-bash-4.1$ grep cabsf\(\) ./gcc/testsuite/gfortran/gfortran.log|wc -l
   38235

(In reply to comment #2)
> --disable-libquadmath-support was enough to build.

Could you try whether using the patch in attachment 23341 [details] (from PR 47648) allows you to build GCC without --disable-libquadmath-support? It copies the configure check from libquadmath to libgfortran.


> However gfortran test results are pretty poor:
> warning: warning: reference to compatibility cabsf()

Looks as if complex numbers are not well supported; I do not quite see why the warning is generated - and for which library.

(libgfortran contains at libgfortran/intrinsics/c99_functions.c a fall-back implementation for cabsf, which uses hypotf, which uses (if not present) hypot.)

Tobias, the patch you mentionned did allow bootstrap with c,fortran and without disabling libquadmath for gcc version 4.6.0 20110212 (experimental) [trunk revision 170072] (GCC).

Feel free to ask for a farm account this will be much more efficient than going through me for each test, instructions here:

http://gcc.gnu.org/wiki/CompileFarm

Building GCC on gcc70/NetBSD is simple:

PATH=/opt/cfarm/dejagnu-1.4.4/bin:$PATH
export MAKE=gmake
cd
svn co svn://gcc.gnu.org/svn/gcc/trunk
cd trunk
contrib/gcc_update
cd
mkdir build
cd build
../trunk/configure --prefix=${HOME}/install-4.6-r170072-c --disable-nls --enable-__cxa_atexit --enable-threads=posix --with-gmp=/opt/cfarm/gmp-5.0.1 --with-mpfr=/opt/cfarm/mpfr-3.0.0 --with-mpc=/opt/cfarm/mpc-0.8.2 --enable-languages=c,fortran
gmake -j 2

Author: burnus
Date: Tue Feb 15 21:30:43 2011
New Revision: 170200

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=170200
Log:
2011-02-15  Tobias Burnus  <burnus@net-b.de>

        PR fortran/47716
        PR fortran/47648
        * acinclude.m4 (LIBGFOR_CHECK_FLOAT128): Use check from
        libquadmath, which uses more features.
        * configure: Regenerate.


Modified:
    trunk/libgfortran/ChangeLog
    trunk/libgfortran/acinclude.m4
    trunk/libgfortran/configure

For reference a verbose version of the testsuite warnings that cause FAIL. I will deactivate fortran in my future builds because otherwise the gcc-testresults@ mail is too big and gets rejected.

-bash-4.1$ gfortran -v -v -v /home/guerby/trunk/gcc/testsuite/gfortran.dg/achar_1.f90 
Driving: gfortran -v -v -v /home/guerby/trunk/gcc/testsuite/gfortran.dg/achar_1.f90 -l gfortran -l m -shared-libgcc
Using built-in specs.
COLLECT_GCC=gfortran
COLLECT_LTO_WRAPPER=/home/guerby/install-4.6-r170072-c/libexec/gcc/x86_64-unknown-netbsd5.1/4.6.0/lto-wrapper
Target: x86_64-unknown-netbsd5.1
Configured with: ../trunk/configure --prefix=/home/guerby/install-4.6-r170072-c --disable-nls --enable-__cxa_atexit --enable-threads=posix --with-gmp=/opt/cfarm/gmp-5.0.1 --with-mpfr=/opt/cfarm/mpfr-3.0.0 --with-mpc=/opt/cfarm/mpc-0.8.2 --enable-languages=c,fortran
Thread model: posix
gcc version 4.6.0 20110212 (experimental) [trunk revision 170072] (GCC) 
COLLECT_GCC_OPTIONS='-v' '-v' '-v' '-shared-libgcc' '-mtune=generic' '-march=x86-64'
 /home/guerby/install-4.6-r170072-c/libexec/gcc/x86_64-unknown-netbsd5.1/4.6.0/f951 /home/guerby/trunk/gcc/testsuite/gfortran.dg/achar_1.f90 -quiet -dumpbase achar_1.f90 -mtune=generic -march=x86-64 -auxbase achar_1 -version -fintrinsic-modules-path /home/guerby/install-4.6-r170072-c/lib/gcc/x86_64-unknown-netbsd5.1/4.6.0/finclude -o /var/tmp//ccZrlOzx.s
GNU Fortran (GCC) version 4.6.0 20110212 (experimental) [trunk revision 170072] (x86_64-unknown-netbsd5.1)
        compiled by GNU C version 4.6.0 20110212 (experimental) [trunk revision 170072], GMP version 5.0.1, MPFR version 3.0.0, MPC version 0.8.2
GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
GNU Fortran (GCC) version 4.6.0 20110212 (experimental) [trunk revision 170072] (x86_64-unknown-netbsd5.1)
        compiled by GNU C version 4.6.0 20110212 (experimental) [trunk revision 170072], GMP version 5.0.1, MPFR version 3.0.0, MPC version 0.8.2
GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
COLLECT_GCC_OPTIONS='-v' '-v' '-v' '-shared-libgcc' '-mtune=generic' '-march=x86-64'
 as -o /var/tmp//cc49hqgX.o /var/tmp//ccZrlOzx.s
Reading specs from /home/guerby/install-4.6-r170072-c/lib/gcc/x86_64-unknown-netbsd5.1/4.6.0/../../../libgfortran.spec
rename spec lib to liborig
COLLECT_GCC_OPTIONS='-v' '-v' '-v' '-shared-libgcc' '-mtune=generic' '-march=x86-64'
COMPILER_PATH=/home/guerby/install-4.6-r170072-c/libexec/gcc/x86_64-unknown-netbsd5.1/4.6.0/:/home/guerby/install-4.6-r170072-c/libexec/gcc/x86_64-unknown-netbsd5.1/4.6.0/:/home/guerby/install-4.6-r170072-c/libexec/gcc/x86_64-unknown-netbsd5.1/:/home/guerby/install-4.6-r170072-c/lib/gcc/x86_64-unknown-netbsd5.1/4.6.0/:/home/guerby/install-4.6-r170072-c/lib/gcc/x86_64-unknown-netbsd5.1/
LIBRARY_PATH=/home/guerby/install-4.6-r170072-c/lib/gcc/x86_64-unknown-netbsd5.1/4.6.0/:/home/guerby/install-4.6-r170072-c/lib/gcc/x86_64-unknown-netbsd5.1/4.6.0/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-v' '-v' '-v' '-shared-libgcc' '-mtune=generic' '-march=x86-64'
 /home/guerby/install-4.6-r170072-c/libexec/gcc/x86_64-unknown-netbsd5.1/4.6.0/collect2 -dc -dp -e _start -dynamic-linker /usr/libexec/ld.elf_so /usr/lib/crt0.o /usr/lib/crti.o /home/guerby/install-4.6-r170072-c/lib/gcc/x86_64-unknown-netbsd5.1/4.6.0/crtbegin.o -L/home/guerby/install-4.6-r170072-c/lib/gcc/x86_64-unknown-netbsd5.1/4.6.0 -L/home/guerby/install-4.6-r170072-c/lib/gcc/x86_64-unknown-netbsd5.1/4.6.0/../../.. /var/tmp//cc49hqgX.o -lgfortran -lm -lgcc_s -lgcc -lm -lgcc_s -lgcc -lc -lgcc_s -lgcc /home/guerby/install-4.6-r170072-c/lib/gcc/x86_64-unknown-netbsd5.1/4.6.0/crtend.o /usr/lib/crtn.o
/home/guerby/install-4.6-r170072-c/lib/gcc/x86_64-unknown-netbsd5.1/4.6.0/../../../libgfortran.so: warning: warning: reference to compatibility cabsf()
/home/guerby/install-4.6-r170072-c/lib/gcc/x86_64-unknown-netbsd5.1/4.6.0/../../../libgfortran.so: warning: warning: reference to compatibility cabs()

(In reply to comment #6)
> warning: warning: reference to compatibility cabsf()

That seems to be a warning generated by NetBSD's libm, cf.
http://mirror.leaseweb.com/NetBSD/NetBSD-release-5-0/src/lib/libm/compat/compat_cabsf.c

That file contains:

float cabsf __P((struct complex));
__warn_references(cabsf, "warning: reference to compatibility cabsf()");

float
cabsf(struct complex z)
{
  return hypotf(z.x, z.y);
}

Which causes the warning. The __warn_references is defined in <sys/cdefs.h>.

Thus, you could also try to silence the warning. hypot(f) should be give an equivalent result to cabs(f) - thus I do not understand why there is a warning at the first place. (Depending, of course, on the quality of the hypot(f) implementation.)


As the warning is due to NetBSD itself and as the quadmath_weak.h issue is solved, I close this PR.

It would be nice if one could silence the warning - and again build with Fortran support.

Looks like a workaround for a similar problem was discussed here but not commited:

http://www.mailinglistarchive.com/fortran@gcc.gnu.org/msg17593.html
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39570

Fixed as per comment #7.