m4 build errors

I'm trying to build m4 on a Solaris platform, and the make is failing with:

source='strtod.c' object='strtod.o' libtool=no \
       DEPDIR=.deps depmode=none /bin/bash ../build-aux/depcomp \
       gcc -std=gnu99  -I.     -g -O2 -c strtod.c
strtod.c: In function 'rpl_strtod':
strtod.c:155: error: incompatible types in assignment
strtod.c:170: error: incompatible types in assignment
strtod.c:257: error: wrong type argument to unary minus
make[3]: *** [strtod.o] Error 1