Thanks. Two more problems:
1) The Makefile.in contains no rules for creating the c files from cmod. I had too add these lines:
tree.c : tree.cmod
inttree.c : inttree.cmod
floattree.c : floattree.cmod
2) After that, inttree.c was generated, but did not compile:
Compiling inttree.c /tmp/pike/src/post_modules/CritBit/inttree.cmod:41:10: error: expected '=', ',', ';', 'asm' or '__attribute__' before string constant
This is the generated code:
[...] static int IntTree_program_fun_num=-1; #line 41 "/tmp/pike/src/post_modules/CritBit/inttree.cmod" SET_TVAR "iterator_class" "Iterator"; SET_TVAR "tree_class" "IntTree"; SET_TVAR "OBJ2_TREE" "OBJ2_INTTREE"; [...]
It looks like a definition of "SET_TVAR" is missing somewhere...