Protect internal symbols from uninterning.

Issue: TXR holds numerous symbol references in global
variables, like list_s. These variables are not registered as
root pointers with the garbage collector. This is normally
okay because symbols are reachable via packages. However,
if such a symbol is uninterned, that causes an integrity problem.

Solution: protect those symbols from being removed from their
packages.

* Makefile (OBJS): Add protsym.o.

* genprotsym.txr, protsym.c: New files.

* lib.c (prot_sym_check): New static function.
(use_sym, uintern, rehome_sym): Use prot_sym_check to
implement a defense against internal symbols being booted
out of their package.

1 files changed, 1 insertions, 1 deletions

diff --git a/Makefile b/Makefile
index b5f164ce..7bf1d3db 100644
--- a/Makefile
+++ b/Makefile
@@ -49,7 +49,7 @@ EXTRA_OBJS-y :=
 
 OBJS := txr.o lex.yy.o y.tab.o match.o lib.o regex.o gc.o unwind.o stream.o
 OBJS += arith.o hash.o utf8.o filter.o eval.o parser.o rand.o combi.o sysif.o
-OBJS += args.o lisplib.o cadr.o struct.o jmp.o
+OBJS += args.o lisplib.o cadr.o struct.o jmp.o protsym.o
 OBJS-$(debug_support) += debug.o
 OBJS-$(have_syslog) += syslog.o
 OBJS-$(have_glob) += glob.o