From: Sergei Trofimovich <siarh...@google.com>
There are 3 GC root tables:
gt_ggc_rtab
gt_ggc_deletable_rtab
gt_pch_scalar_rtab
`deletable` and `scalar` tables are both simple: each element always
contains a pointer to the beginning of the object and it's size is the
full object.
`rtab` is different: it's `base` is a pointer in the middle of the
struct and `stride` points to the next GC pointer in the array.
Before the change there were 2 problems:
1. We memset()ed not just pointers but data around them.
2. We wen out of bounds of the last object described by gt_ggc_rtab
and triggered bootstrap failures in profile and asan bootstraps.
After the change we handle only pointers themselves like the rest of
ggc-common.cc code.
gcc/
PR/111505
* ggc-common.cc (ggc_zero_out_root_pointers): New helper.
* ggc-common.cc (ggc_common_finalize): Use helper instead of
memset() to wipe out pointers.
---
gcc/ggc-common.cc | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/gcc/ggc-common.cc b/gcc/ggc-common.cc
index 95803fa95a1..39e2581affd 100644
--- a/gcc/ggc-common.cc
+++ b/gcc/ggc-common.cc
@@ -75,6 +75,18 @@ ggc_mark_root_tab (const_ggc_root_tab_t rt)
(*rt->cb) (*(void **) ((char *)rt->base + rt->stride * i));
}
+/* Zero out all the roots in the table RT. */
+
+static void
+ggc_zero_rtab_roots (const_ggc_root_tab_t rt)
+{
+ size_t i;
+
+ for ( ; rt->base != NULL; rt++)
+ for (i = 0; i < rt->nelt; i++)
+ (*(void **) ((char *)rt->base + rt->stride * i)) = (void*)0;
+}
+
/* Iterate through all registered roots and mark each element. */
void
@@ -1307,8 +1319,7 @@ ggc_common_finalize ()
memset (rti->base, 0, rti->stride * rti->nelt);
for (rt = gt_ggc_rtab; *rt; rt++)
- for (rti = *rt; rti->base != NULL; rti++)
- memset (rti->base, 0, rti->stride * rti->nelt);
+ ggc_zero_rtab_roots (*rt);
for (rt = gt_pch_scalar_rtab; *rt; rt++)
for (rti = *rt; rti->base != NULL; rti++)
--
2.42.0
