On 5/1/24 21:34, Nathaniel Shead wrote:
On Thu, May 02, 2024 at 12:15:44AM +1000, Nathaniel Shead wrote:
On Wed, May 01, 2024 at 09:57:38AM -0400, Patrick Palka wrote:
On Wed, 1 May 2024, Nathaniel Shead wrote:
Bootstrapped and regtested on x86_64-pc-linux-gnu, OK for trunk (and
later 14.2)? I don't think making it a GTY root is necessary but I felt
perhaps better to be safe than sorry.
Potentially another approach would be to use DECL_UID instead like how
entity_map does; would that be preferable?
-- >8 --
I got notified by Linaro CI and by checking testresults that there seems
to be some occasional failures in tpl-friend-4_b.C on some architectures
and standards modes since r15-59-gb5f6a56940e708. I haven't been able
to reproduce but looking at the backtrace I suspect the issue is that
we're adding to the 'imported_temploid_friend' map a decl that is
ultimately discarded, which then has its address reused by a later decl
causing a failure in the assert in 'set_originating_module'.
This patch attempts to fix the issue in two ways: by ensuring that we
only store the decl if we know it's a new decl (and hence won't be
discarded), and by making the imported_temploid_friends map a GTY root
so that even if the decl does get discarded later the address isn't
reused.
gcc/cp/ChangeLog:
* module.cc (imported_temploid_friends): Mark GTY, and...
(init_modules): ...allocate from GGC.
(trees_in::decl_value): Only write to imported_temploid_friends
for new decls.
Signed-off-by: Nathaniel Shead <nathanielosh...@gmail.com>
---
gcc/cp/module.cc | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index 5b8ff5bc483..37d38bb9654 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -2731,7 +2731,7 @@ static keyed_map_t *keyed_table;
need to be attached to the same module as the temploid. This maps
these decls to the temploid they are instantiated them, as there is
no other easy way to get this information. */
-static hash_map<tree, tree> *imported_temploid_friends;
+static GTY(()) hash_map<tree, tree> *imported_temploid_friends;
/********************************************************************/
/* Tree streaming. The tree streaming is very specific to the tree
@@ -8327,7 +8327,8 @@ trees_in::decl_value ()
if (TREE_CODE (inner) == FUNCTION_DECL
|| TREE_CODE (inner) == TYPE_DECL)
if (tree owner = tree_node ())
- imported_temploid_friends->put (decl, owner);
+ if (is_new)
+ imported_temploid_friends->put (decl, owner);
Hmm, I'm not seeing this code path getting reached for tpl-friend-4_b.C.
It seems we're instead adding to imported_temploid_friends from
propagate_defining_module, during tsubst_friend_function.
What seems to be happening is that we we first tsubst_friend_function
'foo' from TPL<int>, and then we tsubst_friend_function 'foo' from DEF<int>,
which ends up calling duplicate_decls, which ggc_frees this 'foo'
redeclaration that is still present in the imported_temploid_friends map.
So I don't think marking imported_temploid_friends as a GC root would
help with this situation. If we want to keep imported_temploid_friends
as a tree -> tree map, I think we just need to ensure that a decl
is removed from the map upon getting ggc_free'd from e.g. duplicate_decls.
Could we instead move the call to propagate_defining_module down a few
lines, after the pushdecl?
But it seems simpler to use DECL_UID as the key instead, since those
never get reused even after the decl gets ggc_free'd IIUC.
It still means garbage entries in the hash_map, which is undesirable
even if it doesn't cause the same kind of breakage.
Incidentally, decl_tree_map is preferable to hash_map<tree,tree> when
the key is always a decl.
Jason
