New: stack overflow protection.

* configure: detect getrlimit, producing HAVE_RLIMIT in
config.h.

* eval.c (do_eval, do_expand): Call gc_stack_check inline
function to check stack pointer against limit.

* gc.c (gc_stack_bottom): Static becomes extern, so inline
function in gc.h can refer to it.
(gc_stack_limit): New global variable.
(gc_init): If we have rlimit, then probe RLIMIT_STACK.
If the stack is sufficiently large, then enable the stack
overflow protection, which kicks in when the stack pointer
appears to be within a certain percentage of the limit.
(set_stack_limit, get_stack_limit): New static functions.
(gc_late_init): Register set-stack-limit and get-stack-limit
intrinsics.
(gc_stack_overflow): New function.

* gc.h (gc_stack_bottom, gc_stack_limit, gc_stack_overflow):
Declared.
(gc_stack_check): New inline function.

* lib.c (stack_overflow_s): New symbol variable.
(obj_print_impl): Call gc_stack_check to protect recursive
printing againts overflow.

* lib.h (stack_overflow_s): Declared.

* unwind.c (uw_init): Register stack-overflow symbol as a an
exception symbol subtyped from error.
(uw_unwind_to_exit_point): When dealing with an unhandled
exception, turn off the stack limit, so we can print the
messages without triggering it in a loop.

* vm.c (vm_execute_closure, vm_funcall_common): Insert
gc_stack_check to the top of the execution of every VM
function.

* txr.1: Documented.

* share/txr/stdlib/doc-syms.tl: Updated.

1 files changed, 1 insertions, 1 deletions

diff --git a/lib.h b/lib.h
index 262d6468..97a7dbd4 100644
--- a/lib.h
+++ b/lib.h
@@ -517,7 +517,7 @@ extern val eof_s, eol_s, assert_s, name_s;
 extern val error_s, type_error_s, internal_error_s, panic_s;
 extern val numeric_error_s, range_error_s;
 extern val query_error_s, file_error_s, process_error_s, syntax_error_s;
-extern val timeout_error_s, system_error_s, alloc_error_s;
+extern val timeout_error_s, system_error_s, alloc_error_s, stack_overflow_s;
 extern val path_not_found_s, path_exists_s, path_permission_s;
 extern val warning_s, defr_warning_s, restart_s, continue_s;
 extern val gensym_counter_s, length_s;