>From 5018b663c6c0d31f27fb44630a69d9e0bd73273d Mon Sep 17 00:00:00 2001 From: Paul Eggert Date: Sat, 20 Jul 2019 19:40:03 -0700 Subject: [PATCH 4/6] Inhibit GC after inhibit_garbage_collection Without this patch, there are unlikely ways that garbage collection could occur (sometimes causing undefined behavior) even when inhibit_garbage_collection is in effect. * src/alloc.c (garbage_collection_inhibited): New var. (pure_alloc): Increment it if pure space is exhausted, so that garbage_collect_1 no longer needs to inspect pure_bytes_used_before_overflow. (allow_garbage_collection): New function. (inhibit_garbage_collection): Increment the new variable rather than specbinding a user variable. (garbage_collect_1): Do not garbage collect if the new variable is set, rather than if pure_bytes_used_before_overflow is set. --- src/alloc.c | 21 +++++++++++++++++---- 1 file changed, 17 insertions(+), 4 deletions(-) diff --git a/src/alloc.c b/src/alloc.c index 9d18fd918b..09b3a4ea7e 100644 --- a/src/alloc.c +++ b/src/alloc.c @@ -292,6 +292,10 @@ #define PUREBEG (char *) pure static ptrdiff_t pure_bytes_used_non_lisp; +/* If positive, garbage collection is inhibited. Otherwise, zero. */ + +static intptr_t garbage_collection_inhibited; + /* If nonzero, this is a warning delivered by malloc and not yet displayed. */ @@ -5120,6 +5124,10 @@ pure_alloc (size_t size, int type) pure_bytes_used_before_overflow += pure_bytes_used - size; pure_bytes_used = 0; pure_bytes_used_lisp = pure_bytes_used_non_lisp = 0; + + /* Can't GC if pure storage overflowed because we can't determine + if something is a pure object or not. */ + garbage_collection_inhibited++; goto again; } @@ -5486,12 +5494,19 @@ staticpro (Lisp_Object const *varaddress) /* Temporarily prevent garbage collection. */ +static void +allow_garbage_collection (void) +{ + garbage_collection_inhibited--; +} + ptrdiff_t inhibit_garbage_collection (void) { ptrdiff_t count = SPECPDL_INDEX (); - specbind (Qgc_cons_threshold, make_fixnum (MOST_POSITIVE_FIXNUM)); + record_unwind_protect_void (allow_garbage_collection); + garbage_collection_inhibited++; return count; } @@ -5779,9 +5794,7 @@ garbage_collect_1 (struct gcstat *gcst) eassert (weak_hash_tables == NULL); - /* Can't GC if pure storage overflowed because we can't determine - if something is a pure object or not. */ - if (pure_bytes_used_before_overflow) + if (garbage_collection_inhibited) return false; /* Record this function, so it appears on the profiler's backtraces. */ -- 2.17.1