[Glibc-bsd-hackers] cpp error: attempt to use poisoned "CPP_PREDEFINES"

[Robert Millan]

Hi!

I'm trying to update Bruno Haible's patch for GCC to support GNU/KFreeBSD,
but hit this strange CPP error. The macro is being #undefed and then #defined,
so I don't understand what the error is about. Anyone knows what "poisoned"
means here?

gcc -c   -g -O2 -DIN_GCC   -W -Wall -Wwrite-strings -Wstrict-prototypes 
-Wmissing-prototypes -pedantic -Wno-long-long -fno-common   -DHAVE_CONFIG_H 
-DGENERATOR_FILE    -I. -I. -I../../gcc/gcc -I../../gcc/gcc/. 
-I../../gcc/gcc/../include  ../../gcc/gcc/gengenrtl.c -o gengenrtl.o
In file included from tm.h:11,
                 from ../../gcc/gcc/gengenrtl.c:26:
../../gcc/gcc/config/kfreebsdgnu.h:25:8: attempt to use poisoned 
"CPP_PREDEFINES"
../../gcc/gcc/config/kfreebsdgnu.h:26:9: attempt to use poisoned 
"CPP_PREDEFINES"
make[1]: *** [gengenrtl.o] Error 1

Thanks,

-- 
Robert Millan

"[..] but the delight and pride of Aule is in the deed of making, and in the
thing made, and neither in possession nor in his own mastery; wherefore he
gives and hoards not, and is free from care, passing ever on to some new work."

 -- J.R.R.T, Ainulindale (Silmarillion)