Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look
OK for trunk
-- >8 --
It turns out that with modules we can call mangle_decl recursively,
which is a problem because the global mangling state isn't recursion
aware. The recursion happens from write_closure_type_name, which calls
lambda_function, which performs name lookup, which can trigger lazy
loading, which can call maybe_clone_body for a newly loaded cdtor, which
can inspect DECL_ASSEMBLER_NAME, which enters mangling. This was observed
when using fmtlib as a module with trunk and it leads to a bogus
"mangling conflicts with a previous mangle error" followed by an ICE
from cdtor_comdat_group due to a mangling mismatch.
This patch fixes this by sidestepping lazy loading when performing the
op() lookup in lambda_function, so that we don't accidentally end up
entering mangling recursively. This should be safe since the lazy load
should still get triggered by some other name lookup.
In passing it was noticed that lazy loading can get quite recursive
ultimately due to the name lookups from check_local_shadow, which may
perform lazy loading, which cause us to instantiate/clone things, which
end up calling check_local_shadow. This patch fixes this by
implementating an optimization suggested by Jason:
> I think we shouldn't bother with check_local_shadow in a clone or
> instantiation, only when actually parsing.
This reduces the maximum depth of lazy loading recursion for a simple
modular Hello World from ~115 to ~12.
gcc/cp/ChangeLog:
* lambda.cc (lambda_function): Call get_class_binding_direct
instead of lookup_member to sidestep lazy loading.
* name-lookup.cc (check_local_shadow): Punt if we're in a
function context that's definitely not actual parsing.
---
gcc/cp/lambda.cc | 4 +---
gcc/cp/name-lookup.cc | 17 +++++++++++++++++
2 files changed, 18 insertions(+), 3 deletions(-)
diff --git a/gcc/cp/lambda.cc b/gcc/cp/lambda.cc
index 1d37e5a52b9..4b1f9391fee 100644
--- a/gcc/cp/lambda.cc
+++ b/gcc/cp/lambda.cc
@@ -175,9 +175,7 @@ lambda_function (tree lambda)
if (CLASSTYPE_TEMPLATE_INSTANTIATION (type)
&& !COMPLETE_OR_OPEN_TYPE_P (type))
return NULL_TREE;
- lambda = lookup_member (type, call_op_identifier,
- /*protect=*/0, /*want_type=*/false,
- tf_warning_or_error);
+ lambda = get_class_binding_direct (type, call_op_identifier);
if (lambda)
lambda = STRIP_TEMPLATE (get_first_fn (lambda));
return lambda;
diff --git a/gcc/cp/name-lookup.cc b/gcc/cp/name-lookup.cc
index e58f3b5cb4d..ca5ba87bc76 100644
--- a/gcc/cp/name-lookup.cc
+++ b/gcc/cp/name-lookup.cc
@@ -3275,6 +3275,23 @@ check_local_shadow (tree decl)
if (TREE_CODE (decl) == PARM_DECL && !DECL_CONTEXT (decl))
return NULL_TREE;
+ if (DECL_FUNCTION_SCOPE_P (decl))
+ {
+ tree ctx = DECL_CONTEXT (decl);
+ if (DECL_CLONED_FUNCTION_P (ctx)
+ || DECL_TEMPLATE_INSTANTIATED (ctx)
+ || (DECL_LANG_SPECIFIC (ctx)
+ && DECL_DEFAULTED_FN (ctx))
+ || (LAMBDA_FUNCTION_P (ctx)
+ && LAMBDA_EXPR_REGEN_INFO (CLASSTYPE_LAMBDA_EXPR
+ (DECL_CONTEXT (ctx)))))
+ /* It suffices to check shadowing only when actually parsing.
+ So punt for clones, instantiations, defaulted functions and
+ regenerated lambdas. This optimization helps lazy loading
+ cascades with modules. */
+ return NULL_TREE;
+ }
+
tree old = NULL_TREE;
cp_binding_level *old_scope = NULL;
if (cxx_binding *binding = outer_binding (DECL_NAME (decl), NULL, true))
--
2.43.0.561.g235986be82
