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, 32 insertions, 0 deletions

diff --git a/genprotsym.txr b/genprotsym.txr
new file mode 100644
index 00000000..7d9f8c2a
--- /dev/null
+++ b/genprotsym.txr
@@ -0,0 +1,32 @@
+@(next (open-files (glob "*.c")))
+@(collect :vars (sym))
+val @(coll)@{sym /[A-Za-z0-9_]+_[sk]/}@/[,;]/@(end)
+@(end)
+@(next "lib.c")
+@(collect)
+@copyright
+@(until)
+
+@(end)
+@(flatten sym)
+@(bind gsym @(tuples 5 (sort sym)))
+@(output "protsym.c")
+/* This file is generated by genprotsym.txr */
+
+@{copyright "\n"}
+
+#include <stddef.h>
+#include "config.h"
+#include "lib.h"
+
+@  (repeat)
+extern val @(rep)@gsym, @(last)@gsym;@(end)
+@  (end)
+
+val *protected_sym[] = {
+@  (repeat)
+  @(rep)&@gsym, @(last)&@gsym,@(end)
+@  (end)
+  convert(val *, 0)
+};
+@(end)