Bootstrapped and regtested on x86_64-pc-linux-gnu, does this approach
look reasonable?
-- >8 --
One known missing piece in the modules implementation is merging of a
streamed-in local class with the corresponding in-TU version of the
local class. This missing piece turns out to cause a hard-to-reduce
use-after-free GC issue due to the entity_ary not being marked as a GC
root (deliberately), and manifests as a serialization error on stream-in
as in PR99426 (see comment #6 for a reduction). It's also reproducible
on trunk when running the xtreme-header tests without -fno-module-lazy.
This patch makes us merge such local classes according to their position
within the containing function's definition, similar to how we merge
FIELD_DECLs of a class according to their index in the TYPE_FIELDS
list.
PR c++/99426
gcc/cp/ChangeLog:
* module.cc (merge_kind::MK_local_class): New enumerator.
(merge_kind_name): Update.
(trees_out::chained_decls): Move BLOCK-specific handling
of DECL_LOCAL_DECL_P decls to ...
(trees_out::core_vals) <case BLOCK>: ... here. Stream
BLOCK_VARS manually.
(trees_in::core_vals) <case BLOCK>: Stream BLOCK_VARS
manually. Handle deduplicated local classes.
(trees_out::key_local_class): Define.
(trees_in::key_local_class): Define.
(trees_out::get_merge_kind) <case FUNCTION_DECL>: Return
MK_local_class for a local class.
(trees_out::key_mergeable) <case FUNCTION_DECL>: Use
key_local_class.
(trees_in::key_mergeable) <case FUNCTION_DECL>: Likewise.
(trees_in::is_matching_decl): Be flexible with type mismatches
for local entities.
gcc/testsuite/ChangeLog:
* g++.dg/modules/xtreme-header-7_a.H: New test.
* g++.dg/modules/xtreme-header-7_b.C: New test.
---
gcc/cp/module.cc | 167 +++++++++++++++---
.../g++.dg/modules/xtreme-header-7_a.H | 4 +
.../g++.dg/modules/xtreme-header-7_b.C | 6 +
3 files changed, 149 insertions(+), 28 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/modules/xtreme-header-7_a.H
create mode 100644 gcc/testsuite/g++.dg/modules/xtreme-header-7_b.C
diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index fa91c6ff9cb..f77f73a59ed 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -2771,6 +2771,7 @@ enum merge_kind
MK_enum, /* Found by CTX, & 1stMemberNAME. */
MK_keyed, /* Found by key & index. */
+ MK_local_class, /* Found by CTX, index. */
MK_friend_spec, /* Like named, but has a tmpl & args too. */
MK_local_friend, /* Found by CTX, index. */
@@ -2799,7 +2800,7 @@ static char const *const merge_kind_name[MK_hwm] =
"unique", "named", "field", "vtable", /* 0...3 */
"asbase", "partial", "enum", "attached", /* 4...7 */
- "friend spec", "local friend", NULL, NULL, /* 8...11 */
+ "local class", "friend spec", "local friend", NULL, /* 8...11 */
NULL, NULL, NULL, NULL,
"type spec", "type tmpl spec", /* 16,17 type (template). */
@@ -2928,6 +2929,7 @@ public:
unsigned binfo_mergeable (tree *);
private:
+ tree key_local_class (const merge_key&, tree);
uintptr_t *find_duplicate (tree existing);
void register_duplicate (tree decl, tree existing);
/* Mark as an already diagnosed bad duplicate. */
@@ -3086,6 +3088,7 @@ public:
void binfo_mergeable (tree binfo);
private:
+ void key_local_class (merge_key&, tree, tree);
bool decl_node (tree, walk_kind ref);
void type_node (tree);
void tree_value (tree);
@@ -4952,18 +4955,7 @@ void
trees_out::chained_decls (tree decls)
{
for (; decls; decls = DECL_CHAIN (decls))
- {
- if (VAR_OR_FUNCTION_DECL_P (decls)
- && DECL_LOCAL_DECL_P (decls))
- {
- /* Make sure this is the first encounter, and mark for
- walk-by-value. */
- gcc_checking_assert (!TREE_VISITED (decls)
- && !DECL_TEMPLATE_INFO (decls));
- mark_by_value (decls);
- }
- tree_node (decls);
- }
+ tree_node (decls);
tree_node (NULL_TREE);
}
@@ -6204,7 +6196,21 @@ trees_out::core_vals (tree t)
/* DECL_LOCAL_DECL_P decls are first encountered here and
streamed by value. */
- chained_decls (t->block.vars);
+ for (tree decls = t->block.vars; decls; decls = DECL_CHAIN (decls))
+ {
+ if (VAR_OR_FUNCTION_DECL_P (decls)
+ && DECL_LOCAL_DECL_P (decls))
+ {
+ /* Make sure this is the first encounter, and mark for
+ walk-by-value. */
+ gcc_checking_assert (!TREE_VISITED (decls)
+ && !DECL_TEMPLATE_INFO (decls));
+ mark_by_value (decls);
+ }
+ tree_node (decls);
+ }
+ tree_node (NULL_TREE);
+
/* nonlocalized_vars is a middle-end thing. */
WT (t->block.subblocks);
WT (t->block.supercontext);
@@ -6717,7 +6723,34 @@ trees_in::core_vals (tree t)
case BLOCK:
t->block.locus = state->read_location (*this);
t->block.end_locus = state->read_location (*this);
- t->block.vars = chained_decls ();
+
+ for (tree *chain = &t->block.vars;;)
+ if (tree decl = tree_node ())
+ {
+ /* For a deduplicated local class, chain the to-be-discarded
+ decl not the in-TU decl (which is already chained to in-TU
+ entities). */
+ if (is_duplicate (decl))
+ decl = maybe_duplicate (decl);
+ else if (DECL_IMPLICIT_TYPEDEF_P (decl)
+ && TYPE_TEMPLATE_INFO (TREE_TYPE (decl)))
+ {
+ tree tmpl = TYPE_TI_TEMPLATE (TREE_TYPE (decl));
+ if (DECL_TEMPLATE_RESULT (tmpl) == decl && is_duplicate (tmpl))
+ decl = DECL_TEMPLATE_RESULT (maybe_duplicate (tmpl));
+ }
+
+ if (!DECL_P (decl) || DECL_CHAIN (decl))
+ {
+ set_overrun ();
+ break;
+ }
+ *chain = decl;
+ chain = &DECL_CHAIN (decl);
+ }
+ else
+ break;
+
/* nonlocalized_vars is middle-end. */
RT (t->block.subblocks);
RT (t->block.supercontext);
@@ -10335,6 +10368,83 @@ trees_in::fn_parms_fini (int tag, tree fn, tree
existing, bool is_defn)
}
}
+/* Encode into KEY the position of the local class declaration DECL
+ within FN. The position is encoded as the index of the innermost
+ BLOCK (numbered in BFS order) along with the index within its
+ BLOCK_VARS list. */
+
+void
+trees_out::key_local_class (merge_key& key, tree decl, tree fn)
+{
+ auto_vec<tree, 4> blocks;
+ blocks.quick_push (DECL_INITIAL (fn));
+ unsigned block_ix = 0;
+ while (block_ix != blocks.length ())
+ {
+ tree block = blocks[block_ix];
+ unsigned decl_ix = 0;
+ for (tree var = BLOCK_VARS (block); var; var = DECL_CHAIN (var))
+ {
+ if (TREE_CODE (var) != TYPE_DECL)
+ continue;
+ if (var == decl)
+ {
+ key.index = (block_ix << 10) | decl_ix;
+ return;
+ }
+ ++decl_ix;
+ }
+ for (tree sub = BLOCK_SUBBLOCKS (block); sub; sub = BLOCK_CHAIN (sub))
+ blocks.safe_push (sub);
+ ++block_ix;
+ }
+
+ /* Not-found value. */
+ key.index = 1023;
+}
+
+/* Look up the local class corresponding at the position encoded by
+ KEY within FN. */
+
+tree
+trees_in::key_local_class (const merge_key& key, tree fn)
+{
+ if (!DECL_INITIAL (fn))
+ return NULL_TREE;
+
+ const unsigned block_pos = key.index >> 10;
+ const unsigned decl_pos = key.index & 1023;
+
+ if (decl_pos == 1023)
+ return NULL_TREE;
+
+ auto_vec<tree, 4> blocks;
+ blocks.quick_push (DECL_INITIAL (fn));
+ unsigned block_ix = 0;
+ while (block_ix != blocks.length ())
+ {
+ tree block = blocks[block_ix];
+ if (block_ix == block_pos)
+ {
+ unsigned decl_ix = 0;
+ for (tree var = BLOCK_VARS (block); var; var = DECL_CHAIN (var))
+ {
+ if (TREE_CODE (var) != TYPE_DECL)
+ continue;
+ if (decl_ix == decl_pos)
+ return var;
+ ++decl_ix;
+ }
+ return NULL_TREE;
+ }
+ for (tree sub = BLOCK_SUBBLOCKS (block); sub; sub = BLOCK_CHAIN (sub))
+ blocks.safe_push (sub);
+ ++block_ix;
+ }
+
+ return NULL_TREE;
+}
+
/* DEP is the depset of some decl we're streaming by value. Determine
the merging behaviour. */
@@ -10454,17 +10564,10 @@ trees_out::get_merge_kind (tree decl, depset *dep)
gcc_unreachable ();
case FUNCTION_DECL:
- // FIXME: This can occur for (a) voldemorty TYPE_DECLS
- // (which are returned from a function), or (b)
- // block-scope class definitions in template functions.
- // These are as unique as the containing function. While
- // on read-back we can discover if the CTX was a
- // duplicate, we don't have a mechanism to get from the
- // existing CTX to the existing version of this decl.
gcc_checking_assert
(DECL_IMPLICIT_TYPEDEF_P (STRIP_TEMPLATE (decl)));
- mk = MK_unique;
+ mk = MK_local_class;
break;
case RECORD_TYPE:
@@ -10768,6 +10871,10 @@ trees_out::key_mergeable (int tag, merge_kind mk, tree
decl, tree inner,
}
break;
+ case MK_local_class:
+ key_local_class (key, STRIP_TEMPLATE (decl), container);
+ break;
+
case MK_enum:
{
/* Anonymous enums are located by their first identifier,
@@ -11117,11 +11224,10 @@ trees_in::key_mergeable (int tag, merge_kind mk, tree
decl, tree inner,
break;
case FUNCTION_DECL:
- // FIXME: What about a voldemort? how do we find what it
- // duplicates? Do we have to number vmorts relative to
- // their containing function? But how would that work
- // when matching an in-TU declaration?
- kind = "unique";
+ gcc_checking_assert (mk == MK_local_class);
+ existing = key_local_class (key, container);
+ if (existing && inner != decl)
+ existing = TYPE_TI_TEMPLATE (TREE_TYPE (existing));
break;
case TYPE_DECL:
@@ -11374,6 +11480,11 @@ trees_in::is_matching_decl (tree existing, tree decl,
bool is_typedef)
/* Just like duplicate_decls, presum the user knows what
they're doing in overriding a builtin. */
TREE_TYPE (existing) = TREE_TYPE (decl);
+ else if (decl_function_context (decl))
+ /* The type of a mergeable local entity (such as a function scope
+ capturing lambda's closure type fields) can depend on an
+ unmergeable local entity (such as a local variable), so type
+ equality isn't feasible in general for local entities. */;
else
{
// FIXME:QOI Might be template specialization from a module,
diff --git a/gcc/testsuite/g++.dg/modules/xtreme-header-7_a.H
b/gcc/testsuite/g++.dg/modules/xtreme-header-7_a.H
new file mode 100644
index 00000000000..bf7859fba99
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/xtreme-header-7_a.H
@@ -0,0 +1,4 @@
+// { dg-additional-options -fmodule-header }
+
+// { dg-module-cmi {} }
+#include "xtreme-header.h"
diff --git a/gcc/testsuite/g++.dg/modules/xtreme-header-7_b.C
b/gcc/testsuite/g++.dg/modules/xtreme-header-7_b.C
new file mode 100644
index 00000000000..03f3dc1bae6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/xtreme-header-7_b.C
@@ -0,0 +1,6 @@
+// A version of xtreme-header_{a.H,b.C} that doesn't pass
+// -fno-module-lazy.
+// { dg-additional-options -fmodules-ts }
+
+#include "xtreme-header.h"
+import "xtreme-header-7_a.H";
--
2.44.0.rc1.15.g4fc51f00ef
