Something

gcc -B/tools/bin/ ../sysdeps/ieee754/dbl-64/s_isinf.c -c -std=gnu99 -O2 -Wall -Winline -Wstrict-prototypes -Wwrite-strings -g -mpreferred-stack-boundary=4  -fPIC   -Wno-uninitialized -D__NO_MATH_INLINES -D__LIBC_INTERNAL_MATH_INLINES -I../include -I. -I/mnt/LFS/sources/glibc-build/math -I.. -I../libio -I../nptl -I/mnt/LFS/sources/glibc-build -I../sysdeps/i386/elf -I../nptl/sysdeps/unix/sysv/linux/i386/i686 -I../nptl/sysdeps/unix/sysv/linux/i386 -I../nptl/sysdeps/unix/sysv/linux -I../nptl/sysdeps/pthread -I../sysdeps/pthread -I../nptl/sysdeps/unix/sysv -I../nptl/sysdeps/unix -I../nptl/sysdeps/i386/i686 -I../nptl/sysdeps/i386 -I../sysdeps/unix/sysv/linux/i386 -I../sysdeps/unix/sysv/linux -I../sysdeps/gnu -I../sysdeps/unix/common -I../sysdeps/unix/mman -I../sysdeps/unix/inet -I../sysdeps/unix/sysv/i386 -I../sysdeps/unix/sysv -I../sysdeps/unix/i386 -I../sysdeps/unix -I../sysdeps/posix -I../sysdeps/i386/i686/fpu -I../sysdeps/i386/i686 -I../sysdeps/i386/i486 -I../nptl/sysdeps/i386/i486 -I../sysdeps/i386/fpu -I../sysdeps/i386 -I../sysdeps/wordsize-32 -I../sysdeps/ieee754/ldbl-96 -I../sysdeps/ieee754/dbl-64 -I../sysdeps/ieee754/flt-32 -I../sysdeps/ieee754 -I../sysdeps/generic/elf -I../sysdeps/generic -nostdinc -isystem /mnt/LFS/tools/bin/../lib/gcc/i686-pc-linux-gnu/4.0.2/include -isystem /tools/include -D_LIBC_REENTRANT -D_LIBC_REENTRANT -include ../include/libc-symbols.h  -DPIC -DSHARED     -o /mnt/LFS/sources/glibc-build/math/s_isinf.os -MD -MP -MF /mnt/LFS/sources/glibc-build/math/s_isinf.os.dt -MT /mnt/LFS/sources/glibc-build/math/s_isinf.os
../sysdeps/ieee754/dbl-64/s_isinf.c:29: error: 'isinf' aliased to undefined symbol '__isinf'
make[2]: *** [/mnt/LFS/sources/glibc-build/math/s_isinf.os] Error 1
make[2]: Leaving directory `/mnt/LFS/sources/glibc-2.3.5/math'
make[1]: *** [math/subdir_lib] Error 2
make[1]: Leaving directory `/mnt/LFS/sources/glibc-2.3.5'
make: *** [all] Error 2