Correction to COBJ initialization pattern.

In fact, the previosuly documented process is not correct and still
leaves a corruption problem under generational GC (which has been the
default for some time).

* HACKING: Document flaw in the initialization pattern previously
thought to be correct, and show fix.

* hash.c (copy_hash): Fix instance of incorrect pattern.

* regex.c (regex_compile): Likewise.

1 files changed, 2 insertions, 2 deletions

diff --git a/regex.c b/regex.c
index b8e7daec..0c6cf363 100644
--- a/regex.c
+++ b/regex.c
@@ -1668,11 +1668,11 @@ val regex_compile(val regex_sexp, val error_stream)
   } else if (opt_derivative_regex || regex_requires_dv(regex_sexp)) {
     regex_t *regex = coerce(regex_t *, chk_malloc(sizeof *regex));
     val ret;
+    val dv = dv_compile_regex(regex_sexp);
     regex->kind = REGEX_DV;
-    regex->r.dv = nil;
     regex->source = nil;
     ret = cobj(coerce(mem_t *, regex), regex_s, &regex_obj_ops);
-    regex->r.dv = dv_compile_regex(regex_sexp);
+    regex->r.dv = dv;
     regex->source = regex_sexp;
     return ret;
   } else {