>From 6a474a55e68a2bada13db69d4099a4b2de7b1271 Mon Sep 17 00:00:00 2001 From: Paul Eggert Date: Sat, 30 May 2020 10:10:02 -0700 Subject: [PATCH] Be more aggressive in marking objects during GC MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Simplified version of a patch from Pip Cet (Bug#41321#299). * src/alloc.c (maybe_lisp_pointer): Remove. All uses removed. (mark_memory): Also look at the pointer offset by ‘lispsym’, for symbols. --- src/alloc.c | 26 ++++++++++---------------- 1 file changed, 10 insertions(+), 16 deletions(-) diff --git a/src/alloc.c b/src/alloc.c index 1c6b664b22..568fee666f 100644 --- a/src/alloc.c +++ b/src/alloc.c @@ -4585,18 +4585,6 @@ mark_maybe_objects (Lisp_Object const *array, ptrdiff_t nelts) mark_maybe_object (*array); } -/* Return true if P might point to Lisp data that can be garbage - collected, and false otherwise (i.e., false if it is easy to see - that P cannot point to Lisp data that can be garbage collected). - Symbols are implemented via offsets not pointers, but the offsets - are also multiples of LISP_ALIGNMENT. */ - -static bool -maybe_lisp_pointer (void *p) -{ - return (uintptr_t) p % LISP_ALIGNMENT == 0; -} - /* If P points to Lisp data, mark that as live if it isn't already marked. */ @@ -4609,9 +4597,6 @@ mark_maybe_pointer (void *p) VALGRIND_MAKE_MEM_DEFINED (&p, sizeof (p)); #endif - if (!maybe_lisp_pointer (p)) - return; - if (pdumper_object_p (p)) { int type = pdumper_find_object_type (p); @@ -4715,7 +4700,16 @@ mark_memory (void const *start, void const *end) for (pp = start; (void const *) pp < end; pp += GC_POINTER_ALIGNMENT) { - mark_maybe_pointer (*(void *const *) pp); + char *p = *(char *const *) pp; + mark_maybe_pointer (p); + + /* Unmask any struct Lisp_Symbol pointer that make_lisp_symbol + previously disguised by adding the address of 'lispsym'. + On a host with 32-bit pointers and 64-bit Lisp_Objects, + a Lisp_Object might be split into registers saved into + non-adjacent words and P might be the low-order word's value. */ + p += (intptr_t) lispsym; + mark_maybe_pointer (p); verify (alignof (Lisp_Object) % GC_POINTER_ALIGNMENT == 0); if (alignof (Lisp_Object) == GC_POINTER_ALIGNMENT -- 2.17.1