On 4/20/21 2:36 PM, Martin Sebor wrote:
On 4/20/21 2:13 PM, Marek Polacek wrote:
On Tue, Apr 20, 2021 at 02:03:00PM -0600, Martin Sebor via Gcc wrote:
I have a static hash_map object that needs to persist across passes:
static GTY(()) hash_map<tree, bitmap> *map;
I initialize the map like so:
map = hash_map<tree, bitmap>::create_ggc (4);
But I see crashes when accessing the map after adding and removing
some number of entries in a few passes. The crashes are due to
the map having been garbage-collected and the memory allocated to
it poisoned (it has the 0xa5a5a5a5a5a5a5a5 bit pattern that I see
in GDD being written into the map by poison_pages()).
I assumed marking the map pointer GTY(()) would keep the garbage
collector from touching the map. Is there something else I need
to do to keep it from doing that?
Thanks
Martin
PS Just in case it matters, the bitmap in the table is allocated
via BITMAP_ALLOC() with a bitmap_obstack variable defined alongside
the map.
My sense is that this is the problem. What happens if you use
BITMAP_GGC_ALLOC?
Same thing :(
I reduced the problem to the following patch/test case no involving
a bitmap or other pointers. With it applied, GCC reliably crashes.
An example of a stack trace is below the patch. What am I missing?
diff --git a/gcc/gimple.c b/gcc/gimple.c
index 87864f3d0dd..0e6cded166e 100644
--- a/gcc/gimple.c
+++ b/gcc/gimple.c
@@ -2749,11 +2749,21 @@ gimple_call_operator_delete_p (const gcall *stmt)
return false;
}
+typedef int_hash <int, 0, INT_MAX> i_hash;
+
+static GTY(()) hash_map<i_hash, int> *ii_map;
+
/* Return true when STMT is builtins call. */
bool
gimple_call_builtin_p (const gimple *stmt)
{
+ if (!ii_map)
+ ii_map = ii_map->create_ggc (4);
+
+ uintptr_t key = gimple_code (stmt);
+ ii_map->put (key, key);
+
tree fndecl;
if (is_gimple_call (stmt)
&& (fndecl = gimple_call_fndecl (stmt)) != NULL_TREE
during GIMPLE pass: cplxlower0
/src/gcc/master/gcc/testsuite/gcc.dg/builtins-1.c:97:55: internal
compiler error: Segmentation fault
0x1308b30 crash_signal
/src/gcc/master/gcc/toplev.c:327
0xe7eaa0 bool simple_hashmap_traits<default_hash_traits<int_hash<int, 0,
2147483647> >, int>::is_empty<hash_map<int_hash<int, 0, 2147483647>,
int, simple_hashmap_traits<default_hash_traits<int_hash<int, 0,
2147483647> >, int> >::hash_entry>(hash_map<int_hash<int, 0,
2147483647>, int,
simple_hashmap_traits<default_hash_traits<int_hash<int, 0, 2147483647>
>, int> >::hash_entry const&)
/src/gcc/master/gcc/hash-map-traits.h:75
0xe7e36a hash_map<int_hash<int, 0, 2147483647>, int,
simple_hashmap_traits<default_hash_traits<int_hash<int, 0, 2147483647>
>, int> >::hash_entry::is_empty(hash_map<int_hash<int, 0, 2147483647>,
int, simple_hashmap_traits<default_hash_traits<int_hash<int, 0,
2147483647> >, int> >::hash_entry const&)
/src/gcc/master/gcc/hash-map.h:71
0xe7ea32 hash_table<hash_map<int_hash<int, 0, 2147483647>, int,
simple_hashmap_traits<default_hash_traits<int_hash<int, 0, 2147483647>
>, int> >::hash_entry, false,
xcallocator>::is_empty(hash_map<int_hash<int, 0, 2147483647>, int,
simple_hashmap_traits<default_hash_traits<int_hash<int, 0, 2147483647>
>, int> >::hash_entry&)
/src/gcc/master/gcc/hash-table.h:541
0xe7e89d hash_table<hash_map<int_hash<int, 0, 2147483647>, int,
simple_hashmap_traits<default_hash_traits<int_hash<int, 0, 2147483647>
>, int> >::hash_entry, false, xcallocator>::expand()
/src/gcc/master/gcc/hash-table.h:819
0xe7e155 hash_table<hash_map<int_hash<int, 0, 2147483647>, int,
simple_hashmap_traits<default_hash_traits<int_hash<int, 0, 2147483647>
>, int> >::hash_entry, false, xcallocator>::find_slot_with_hash(int
const&, unsigned int, insert_option)
/src/gcc/master/gcc/hash-table.h:964
0xe7d9b8 hash_map<int_hash<int, 0, 2147483647>, int,
simple_hashmap_traits<default_hash_traits<int_hash<int, 0, 2147483647>
>, int> >::put(int const&, int const&)
/src/gcc/master/gcc/hash-map.h:166
0xe7932f gimple_call_builtin_p(gimple const*)
/src/gcc/master/gcc/gimple.c:2766
0xece684 maybe_fold_stmt
/src/gcc/master/gcc/gimplify.c:3303
0xed888e gimplify_modify_expr
/src/gcc/master/gcc/gimplify.c:5994
0xf03d14 gimplify_expr(tree_node**, gimple**, gimple**, bool
(*)(tree_node*), int)
/src/gcc/master/gcc/gimplify.c:14083
0xedbf17 gimplify_stmt(tree_node**, gimple**)
/src/gcc/master/gcc/gimplify.c:6877
0xec55f0 gimplify_and_add(tree_node*, gimple**)
/src/gcc/master/gcc/gimplify.c:489
0xec5d8f internal_get_tmp_var
/src/gcc/master/gcc/gimplify.c:642
0xec5dd6 get_formal_tmp_var(tree_node*, gimple**)
/src/gcc/master/gcc/gimplify.c:663
0xf07a6b gimplify_expr(tree_node**, gimple**, gimple**, bool
(*)(tree_node*), int)
/src/gcc/master/gcc/gimplify.c:15072
0xf0d30a force_gimple_operand_1(tree_node*, gimple**, bool
(*)(tree_node*), tree_node*)
/src/gcc/master/gcc/gimplify-me.c:78
0xf0d3d7 force_gimple_operand_gsi_1(gimple_stmt_iterator*, tree_node*,
bool (*)(tree_node*), tree_node*, bool, gsi_iterator_update)
/src/gcc/master/gcc/gimplify-me.c:115
0xf0d490 force_gimple_operand_gsi(gimple_stmt_iterator*, tree_node*,
bool, tree_node*, bool, gsi_iterator_update)
/src/gcc/master/gcc/gimplify-me.c:141
0x13791c5 gimplify_build1(gimple_stmt_iterator*, tree_code, tree_node*,
tree_node*)
/src/gcc/master/gcc/tree-cfg.c:9249
