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PR c++/91476 - anon-namespace reference temp clash between TUs.

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The problem in the PR was that make_temporary_var_for_ref_to_temp ran before
determine_visibility, so when we copied the linkage of the reference
variable it had not yet been restricted by its anonymous namespace context,
so the temporary wrongly ended up with TREE_PUBLIC set.  The natural
solution is to run determine_visibility earlier.  But that needs to happen
after maybe_commonize_var increases the linkage of some local variables, and
on targets without weak symbol support, that function does different things
based on the results of check_initializer, which is what calls
make_temporary_var_for_ref_to_temp.  To break this circular dependency I'm
calling maybe_commonize_var early, and then again later if the target
doesn't support weak symbols.

It also occurred to me that make_temporary_var_for_ref_to_temp wasn't
handling DECL_VISIBILITY at all, and verified that we were doing the wrong
thing.  So I've combined the linkage-copying code from there and two other
places.

	* decl2.c (copy_linkage): Factor out of get_guard.
	* call.c (make_temporary_var_for_ref_to_temp): Use it.
	* decl.c (cp_finish_decomp): Use it.
	(cp_finish_decl): determine_visibility sooner.
This commit is contained in:
Jason Merrill 2020-01-20 13:27:10 -05:00
parent 56e2cc43de
commit 8158a46408
6 changed files with 63 additions and 41 deletions
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8
gcc/cp/ChangeLog
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@ -1,3 +1,11 @@
2020-01-21 Jason Merrill <jason@redhat.com>
PR c++/91476 - anon-namespace reference temp clash between TUs.
* decl2.c (copy_linkage): Factor out of get_guard.
* call.c (make_temporary_var_for_ref_to_temp): Use it.
* decl.c (cp_finish_decomp): Use it.
(cp_finish_decl): determine_visibility sooner.
2020-01-21 Bin Cheng <bin.cheng@linux.alibaba.com>
* coroutines.cc (finish_co_await_expr): Set return value flag.

9
gcc/cp/call.c
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@ -11973,14 +11973,7 @@ make_temporary_var_for_ref_to_temp (tree decl, tree type)
GR and suffixed with a sequence number mangled using the usual rules
for a seq-id. Temporaries are numbered with a pre-order, depth-first,
left-to-right walk of the complete initializer. */
TREE_STATIC (var) = TREE_STATIC (decl);
TREE_PUBLIC (var) = TREE_PUBLIC (decl);
if (vague_linkage_p (decl))
comdat_linkage (var);
CP_DECL_THREAD_LOCAL_P (var) = CP_DECL_THREAD_LOCAL_P (decl);
set_decl_tls_model (var, DECL_TLS_MODEL (decl));
copy_linkage (var, decl);
tree name = mangle_ref_init_variable (decl);
DECL_NAME (var) = name;

1
gcc/cp/cp-tree.h
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@ -6636,6 +6636,7 @@ extern bool mark_used (tree);
extern bool mark_used (tree, tsubst_flags_t);
extern void finish_static_data_member_decl (tree, tree, bool, tree, int);
extern tree cp_build_parm_decl (tree, tree, tree);
extern void copy_linkage (tree, tree);
extern tree get_guard (tree);
extern tree get_guard_cond (tree, bool);
extern tree set_guard (tree);

33
gcc/cp/decl.c
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@ -7657,6 +7657,14 @@ cp_finish_decl (tree decl, tree init, bool init_const_expr_p,
TREE_READONLY (decl) = 0;
}
/* This needs to happen before extend_ref_init_temps. */
if (VAR_OR_FUNCTION_DECL_P (decl))
{
if (VAR_P (decl))
maybe_commonize_var (decl);
determine_visibility (decl);
}
if (VAR_P (decl))
{
duration_kind dk = decl_storage_duration (decl);
@ -7786,12 +7794,11 @@ cp_finish_decl (tree decl, tree init, bool init_const_expr_p,
if (VAR_P (decl))
{
layout_var_decl (decl);
maybe_commonize_var (decl);
if (!flag_weak)
/* Check again now that we have an initializer. */
maybe_commonize_var (decl);
}
/* This needs to happen after the linkage is set. */
determine_visibility (decl);
if (var_definition_p && TREE_STATIC (decl))
{
/* If a TREE_READONLY variable needs initialization
@ -8328,23 +8335,7 @@ cp_finish_decomp (tree decl, tree first, unsigned int count)
}
if (!processing_template_decl)
{
TREE_PUBLIC (v[i]) = TREE_PUBLIC (decl);
TREE_STATIC (v[i]) = TREE_STATIC (decl);
DECL_COMMON (v[i]) = DECL_COMMON (decl);
DECL_COMDAT (v[i]) = DECL_COMDAT (decl);
if (TREE_STATIC (v[i]))
{
CP_DECL_THREAD_LOCAL_P (v[i])
= CP_DECL_THREAD_LOCAL_P (decl);
set_decl_tls_model (v[i], DECL_TLS_MODEL (decl));
if (DECL_ONE_ONLY (decl))
make_decl_one_only (v[i], cxx_comdat_group (v[i]));
if (TREE_PUBLIC (decl))
DECL_WEAK (v[i]) = DECL_WEAK (decl);
DECL_VISIBILITY (v[i]) = DECL_VISIBILITY (decl);
DECL_VISIBILITY_SPECIFIED (v[i])
= DECL_VISIBILITY_SPECIFIED (decl);
}
copy_linkage (v[i], decl);
cp_finish_decl (v[i], init, /*constexpr*/false,
/*asm*/NULL_TREE, LOOKUP_NORMAL);
}

36
gcc/cp/decl2.c
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@ -3214,6 +3214,29 @@ build_cleanup (tree decl)
return clean;
}
/* GUARD is a helper variable for DECL; make them have the same linkage and
visibility. */
void
copy_linkage (tree guard, tree decl)
{
TREE_PUBLIC (guard) = TREE_PUBLIC (decl);
TREE_STATIC (guard) = TREE_STATIC (decl);
DECL_COMMON (guard) = DECL_COMMON (decl);
DECL_COMDAT (guard) = DECL_COMDAT (decl);
if (TREE_STATIC (guard))
{
CP_DECL_THREAD_LOCAL_P (guard) = CP_DECL_THREAD_LOCAL_P (decl);
set_decl_tls_model (guard, DECL_TLS_MODEL (decl));
/* We can't rely on DECL_WEAK (decl) or DECL_ONE_ONLY (decl) here, as
they may not be set until import_export_decl at EOF. */
if (vague_linkage_p (decl))
comdat_linkage (guard);
DECL_VISIBILITY (guard) = DECL_VISIBILITY (decl);
DECL_VISIBILITY_SPECIFIED (guard) = DECL_VISIBILITY_SPECIFIED (decl);
}
}
/* Returns the initialization guard variable for the variable DECL,
which has static storage duration. */
@ -3236,18 +3259,7 @@ get_guard (tree decl)
VAR_DECL, sname, guard_type);
/* The guard should have the same linkage as what it guards. */
TREE_PUBLIC (guard) = TREE_PUBLIC (decl);
TREE_STATIC (guard) = TREE_STATIC (decl);
DECL_COMMON (guard) = DECL_COMMON (decl);
DECL_COMDAT (guard) = DECL_COMDAT (decl);
CP_DECL_THREAD_LOCAL_P (guard) = CP_DECL_THREAD_LOCAL_P (decl);
set_decl_tls_model (guard, DECL_TLS_MODEL (decl));
if (DECL_ONE_ONLY (decl))
make_decl_one_only (guard, cxx_comdat_group (guard));
if (TREE_PUBLIC (decl))
DECL_WEAK (guard) = DECL_WEAK (decl);
DECL_VISIBILITY (guard) = DECL_VISIBILITY (decl);
DECL_VISIBILITY_SPECIFIED (guard) = DECL_VISIBILITY_SPECIFIED (decl);
copy_linkage (guard, decl);
DECL_ARTIFICIAL (guard) = 1;
DECL_IGNORED_P (guard) = 1;

17
gcc/testsuite/g++.dg/ext/visibility/ref-temp1.C Normal file
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@ -0,0 +1,17 @@
// PR c++/91476
// Test that hidden and internal visibility propagates to reference temps.
#define HIDDEN __attribute((visibility("hidden")))
// { dg-final { scan-hidden "_ZGRZ1fvE3foo_" } }
HIDDEN inline const int* f() { static const int &foo = 1; return &foo; }
// { dg-final { scan-assembler-not "(weak|globl)\[^\n\]*_ZGRN12_GLOBAL__N_13fooE_" } }
namespace { const int &foo = 1; }
const void *volatile p;
int main()
{
p = f();
p = &foo;
}