From 8c94ca94dc2772e5c651de6cf46bfffc388234d5 Mon Sep 17 00:00:00 2001 From: Philipp Stephani Date: Sat, 25 Jul 2020 23:04:05 +0200 Subject: [PATCH] Backport: Fix subtle bug when checking liveness of module values. We can't simply look up the Lisp object in the global reference table because an invalid local and a valid global reference might refer to the same object. Instead, we have to test the address of the global reference against the stored references. * src/emacs-module.c (module_global_reference_p): New helper function. (value_to_lisp): Use it. (cherry picked from commit 6355a3ec62f43c9b99d483982ff851d32dd78891) --- src/emacs-module.c | 27 ++++++++++++++++++++++++--- 1 file changed, 24 insertions(+), 3 deletions(-) diff --git a/src/emacs-module.c b/src/emacs-module.c index 4269b0ba2ac..099a6a3cf25 100644 --- a/src/emacs-module.c +++ b/src/emacs-module.c @@ -78,6 +78,7 @@ To add a new module function, proceed as follows: #include "emacs-module.h" #include +#include #include #include #include @@ -380,6 +381,28 @@ XMODULE_GLOBAL_REFERENCE (Lisp_Object o) return XUNTAG (o, Lisp_Vectorlike, struct module_global_reference); } +/* Returns whether V is a global reference. Only used to check module + assertions. If V is not a global reference, increment *N by the + number of global references (for debugging output). */ + +static bool +module_global_reference_p (emacs_value v, ptrdiff_t *n) +{ + struct Lisp_Hash_Table *h = XHASH_TABLE (Vmodule_refs_hash); + /* Note that we can't use `hash_lookup' because V might be a local + reference that's identical to some global reference. */ + for (ptrdiff_t i = 0; i < HASH_TABLE_SIZE (h); ++i) + { + if (!EQ (HASH_KEY (h, i), Qunbound) + && &XMODULE_GLOBAL_REFERENCE (HASH_VALUE (h, i))->value == v) + return true; + } + /* Only used for debugging, so we don't care about overflow, just + make sure the operation is defined. */ + INT_ADD_WRAPV (*n, h->count, n); + return false; +} + static emacs_value module_make_global_ref (emacs_env *env, emacs_value ref) { @@ -1217,10 +1240,8 @@ value_to_lisp (emacs_value v) ++num_environments; } /* Also check global values. */ - struct Lisp_Hash_Table *h = XHASH_TABLE (Vmodule_refs_hash); - if (hash_lookup (h, v->v, NULL) != -1) + if (module_global_reference_p (v, &num_values)) goto ok; - INT_ADD_WRAPV (num_values, h->count, &num_values); module_abort (("Emacs value not found in %"pD"d values " "of %"pD"d environments"), num_values, num_environments); -- 2.39.2