On Tue, Mar 12, 2024 at 06:26:14PM -0400, Jason Merrill wrote: > On 3/12/24 11:56, Marek Polacek wrote: > > On Tue, Mar 12, 2024 at 09:57:14AM -0400, Jason Merrill wrote: > > > On 3/11/24 19:27, Marek Polacek wrote: > > > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/13? > > > > > > > > -- >8 -- > > > > This ICE started with the fairly complicated r13-765. We crash in > > > > gimplify_var_or_parm_decl because a stray VAR_DECL leaked there. > > > > The problem is ultimately that potential_prvalue_result_of wasn't > > > > correctly handling arrays and replace_placeholders_for_class_temp_r > > > > replaced a PLACEHOLDER_EXPR in a TARGET_EXPR which is used in the > > > > context of copy elision. If I have > > > > > > > > M m[2] = { M{""}, M{""} }; > > > > > > > > then we don't invoke the M(const M&) copy-ctor. I think the fix is > > > > to detect such a case in potential_prvalue_result_of. > > > > > > > > PR c++/109966 > > > > > > > > gcc/cp/ChangeLog: > > > > > > > > * typeck2.cc (potential_prvalue_result_of): Add walk_subtrees > > > > parameter. Handle initializing an array from a > > > > brace-enclosed-initializer. > > > > (replace_placeholders_for_class_temp_r): Pass walk_subtrees > > > > down to > > > > potential_prvalue_result_of. > > > > > > > > gcc/testsuite/ChangeLog: > > > > > > > > * g++.dg/cpp1y/nsdmi-aggr20.C: New test. > > > > * g++.dg/cpp1y/nsdmi-aggr21.C: New test. > > > > --- > > > > gcc/cp/typeck2.cc | 27 ++++++++--- > > > > gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr20.C | 17 +++++++ > > > > gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr21.C | 59 > > > > +++++++++++++++++++++++ > > > > 3 files changed, 96 insertions(+), 7 deletions(-) > > > > create mode 100644 gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr20.C > > > > create mode 100644 gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr21.C > > > > > > > > diff --git a/gcc/cp/typeck2.cc b/gcc/cp/typeck2.cc > > > > index 31198b2f9f5..8b99ce78e9a 100644 > > > > --- a/gcc/cp/typeck2.cc > > > > +++ b/gcc/cp/typeck2.cc > > > > @@ -1406,46 +1406,59 @@ digest_init_flags (tree type, tree init, int > > > > flags, tsubst_flags_t complain) > > > > A a = (A{}); // initializer > > > > A a = (1, A{}); // initializer > > > > A a = true ? A{} : A{}; // initializer > > > > + A arr[1] = { A{} }; // initializer > > > > auto x = A{}.x; // temporary materialization > > > > auto x = foo(A{}); // temporary materialization > > > > FULL_EXPR is the whole expression, SUBOB is its TARGET_EXPR > > > > subobject. */ > > > > static bool > > > > -potential_prvalue_result_of (tree subob, tree full_expr) > > > > +potential_prvalue_result_of (tree subob, tree full_expr, int > > > > *walk_subtrees) > > > > { > > > > +#define RECUR(t) potential_prvalue_result_of (subob, t, walk_subtrees) > > > > if (subob == full_expr) > > > > return true; > > > > else if (TREE_CODE (full_expr) == TARGET_EXPR) > > > > { > > > > tree init = TARGET_EXPR_INITIAL (full_expr); > > > > if (TREE_CODE (init) == COND_EXPR) > > > > - return (potential_prvalue_result_of (subob, TREE_OPERAND (init, > > > > 1)) > > > > - || potential_prvalue_result_of (subob, TREE_OPERAND > > > > (init, 2))); > > > > + return (RECUR (TREE_OPERAND (init, 1)) > > > > + || RECUR (TREE_OPERAND (init, 2))); > > > > else if (TREE_CODE (init) == COMPOUND_EXPR) > > > > - return potential_prvalue_result_of (subob, TREE_OPERAND (init, > > > > 1)); > > > > + return RECUR (TREE_OPERAND (init, 1)); > > > > /* ??? I don't know if this can be hit. */ > > > > else if (TREE_CODE (init) == PAREN_EXPR) > > > > { > > > > gcc_checking_assert (false); > > > > - return potential_prvalue_result_of (subob, TREE_OPERAND > > > > (init, 0)); > > > > + return RECUR (TREE_OPERAND (init, 0)); > > > > } > > > > } > > > > + /* The array case listed above. */ > > > > + else if (TREE_CODE (full_expr) == CONSTRUCTOR > > > > + && TREE_CODE (TREE_TYPE (full_expr)) == ARRAY_TYPE) > > > > + for (constructor_elt &e: CONSTRUCTOR_ELTS (full_expr)) > > > > + if (e.value == subob) > > > > + { > > > > + *walk_subtrees = 0; > > > > > > Why clear walk_subtrees? Won't that mean we fail to replace any > > > placeholders nested within an array element initializer? > > > > Right. I couldn't find a testcase where that would cause a problem > > but I think I just wasn't inventive enough. > > > > Originally, I was checking same_type_ignoring_top_level_qualifiers_p > > but that's not going to work for code like > > > > struct N { N(M); }; > > N arr[2] = { M{""}, M{""} }; > > > > or with operator M(). But I suppose I could just use can_convert > > like below. What do you think about that? > > Basing this on the type seems unreliable, we're looking for where in the > expression the TARGET_EXPR occurs, and there could be others of the same > type elsewhere in the expression. > > Why not loop over CONSTRUCTOR_ELTS like you did above, just without clearing > walk_subtrees?
With the test with N(M) we are dealing with: {TARGET_EXPR <D.2892, <<< Unknown tree: aggr_init_expr 5 __ct_comp D.2892 (struct N *) <<< Unknown tree: void_cst >>> TARGET_EXPR <D.2864, {.name=TARGET_EXPR <D.2854, <<< Unknown tree: aggr_init_expr 5 __ct_comp D.2854 (struct k *) <<< Unknown tree: void_cst >>> (const char *) "" >>>>, .j=NON_LVALUE_EXPR <42>, .i=(&<PLACEHOLDER_EXPR struct M>)->j}> >>>>} where the TARGET_EXPR with slot=D.2864 is the problematic one. So looping over CONSTRUCTOR_ELTS of the outer CONSTRUCTOR wouldn't find it. But you're of course right that just checking the type is fragile. In the following patch, I'm taking a different tack. I believe we ought to use TARGET_EXPR_ELIDING_P. The gimplify_arg bit I'm talking about below is this: /* Also strip a TARGET_EXPR that would force an extra copy. */ if (TREE_CODE (*arg_p) == TARGET_EXPR) { tree init = TARGET_EXPR_INITIAL (*arg_p); if (init && !VOID_TYPE_P (TREE_TYPE (init))) *arg_p = init; } Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/13? -- >8 -- This ICE started with the fairly complicated r13-765. We crash in gimplify_var_or_parm_decl because a stray VAR_DECL leaked there. The problem is ultimately that potential_prvalue_result_of wasn't correctly handling arrays and replace_placeholders_for_class_temp_r replaced a PLACEHOLDER_EXPR in a TARGET_EXPR which is used in the context of copy elision. If I have M m[2] = { M{""}, M{""} }; then we don't invoke the M(const M&) copy-ctor. One part of the fix is to use TARGET_EXPR_ELIDING_P rather than potential_prvalue_result_of. That unfortunately doesn't handle the case like struct N { N(M); }; N arr[2] = { M{""}, M{""} }; because TARGET_EXPRs that initialize a function argument are not marked TARGET_EXPR_ELIDING_P even though gimplify_arg drops such TARGET_EXPRs on the floor. We can use a pset to avoid replacing placeholders in them. I made an attempt to use set_target_expr_eliding in convert_for_arg_passing but that regressed constexpr-diag1.C, and does not seem like a prudent change in stage 4 anyway. PR c++/109966 gcc/cp/ChangeLog: * typeck2.cc (potential_prvalue_result_of): Remove. (replace_placeholders_for_class_temp_r): Check TARGET_EXPR_ELIDING_P. Use a pset. Don't replace_placeholders in TARGET_EXPRs that initialize a function argument. gcc/testsuite/ChangeLog: * g++.dg/cpp1y/nsdmi-aggr20.C: New test. * g++.dg/cpp1y/nsdmi-aggr21.C: New test. --- gcc/cp/typeck2.cc | 55 ++++++--------------- gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr20.C | 17 +++++++ gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr21.C | 59 +++++++++++++++++++++++ 3 files changed, 92 insertions(+), 39 deletions(-) create mode 100644 gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr20.C create mode 100644 gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr21.C diff --git a/gcc/cp/typeck2.cc b/gcc/cp/typeck2.cc index 31198b2f9f5..4bf3201eedc 100644 --- a/gcc/cp/typeck2.cc +++ b/gcc/cp/typeck2.cc @@ -1399,41 +1399,6 @@ digest_init_flags (tree type, tree init, int flags, tsubst_flags_t complain) return digest_init_r (type, init, 0, flags, complain); } -/* Return true if SUBOB initializes the same object as FULL_EXPR. - For instance: - - A a = A{}; // initializer - A a = (A{}); // initializer - A a = (1, A{}); // initializer - A a = true ? A{} : A{}; // initializer - auto x = A{}.x; // temporary materialization - auto x = foo(A{}); // temporary materialization - - FULL_EXPR is the whole expression, SUBOB is its TARGET_EXPR subobject. */ - -static bool -potential_prvalue_result_of (tree subob, tree full_expr) -{ - if (subob == full_expr) - return true; - else if (TREE_CODE (full_expr) == TARGET_EXPR) - { - tree init = TARGET_EXPR_INITIAL (full_expr); - if (TREE_CODE (init) == COND_EXPR) - return (potential_prvalue_result_of (subob, TREE_OPERAND (init, 1)) - || potential_prvalue_result_of (subob, TREE_OPERAND (init, 2))); - else if (TREE_CODE (init) == COMPOUND_EXPR) - return potential_prvalue_result_of (subob, TREE_OPERAND (init, 1)); - /* ??? I don't know if this can be hit. */ - else if (TREE_CODE (init) == PAREN_EXPR) - { - gcc_checking_assert (false); - return potential_prvalue_result_of (subob, TREE_OPERAND (init, 0)); - } - } - return false; -} - /* Callback to replace PLACEHOLDER_EXPRs in a TARGET_EXPR (which isn't used in the context of guaranteed copy elision). */ @@ -1441,11 +1406,13 @@ static tree replace_placeholders_for_class_temp_r (tree *tp, int *, void *data) { tree t = *tp; - tree full_expr = *static_cast<tree *>(data); + auto pset = static_cast<hash_set<tree> *>(data); /* We're looking for a TARGET_EXPR nested in the whole expression. */ if (TREE_CODE (t) == TARGET_EXPR - && !potential_prvalue_result_of (t, full_expr)) + /* That serves as temporary materialization, not an initializer. */ + && !TARGET_EXPR_ELIDING_P (t) + && !pset->add (t)) { tree init = TARGET_EXPR_INITIAL (t); while (TREE_CODE (init) == COMPOUND_EXPR) @@ -1460,6 +1427,16 @@ replace_placeholders_for_class_temp_r (tree *tp, int *, void *data) gcc_checking_assert (!find_placeholders (init)); } } + /* TARGET_EXPRs initializing function arguments are not marked as eliding, + even though gimplify_arg drops them on the floor. Don't go replacing + placeholders in them. */ + else if (TREE_CODE (t) == CALL_EXPR || TREE_CODE (t) == AGGR_INIT_EXPR) + for (int i = 0; i < call_expr_nargs (t); ++i) + { + tree arg = get_nth_callarg (t, i); + if (TREE_CODE (arg) == TARGET_EXPR) + pset->add (arg); + } return NULL_TREE; } @@ -1507,8 +1484,8 @@ digest_nsdmi_init (tree decl, tree init, tsubst_flags_t complain) temporary materialization does not occur when initializing an object from a prvalue of the same type, therefore we must not replace the placeholder with a temporary object so that it can be elided. */ - cp_walk_tree (&init, replace_placeholders_for_class_temp_r, &init, - nullptr); + hash_set<tree> pset; + cp_walk_tree (&init, replace_placeholders_for_class_temp_r, &pset, nullptr); return init; } diff --git a/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr20.C b/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr20.C new file mode 100644 index 00000000000..4796d861e83 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr20.C @@ -0,0 +1,17 @@ +// PR c++/109966 +// { dg-do compile { target c++14 } } + +#define SA(X) static_assert ((X),#X) + +struct A { + int a; + int b = a; +}; + +struct B { + int x = 0; + int y[1]{A{x}.b}; +}; + +constexpr B b = { }; +SA(b.y[0] == 0); diff --git a/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr21.C b/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr21.C new file mode 100644 index 00000000000..efec45bc1a8 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr21.C @@ -0,0 +1,59 @@ +// PR c++/109966 +// { dg-do compile { target c++14 } } + +struct k { + k(const char *); +}; +struct M { + k name; + int j = 42; + int i = j; +}; + +M m = M{""}; + +struct S { + M arr1[1]{M{""}}; + M a1[1] = { (M{""}) }; + M a2[1] = { (true, M{""}) }; + M a3[1] = { true ? M{""} : M{""} }; + M arr2[2]{M{""}, M{""}}; + M arr3[3]{M{""}, M{""}, M{""}}; + + M arr1e[1] = {M{""}}; + M arr2e[2] = {M{""}, M{""}}; + M arr3e[3] = {M{""}, M{""}, M{""}}; + + M arr1l[1] = { m }; + M arr2l[2] = { m, m }; + M arr3l[3] = { m, m, m }; + + M m1 = M{""}; + M m2 = m; + M m3{M{""}}; + M m4 = {M{""}}; +} o; + +struct N { + N(M); +}; + +struct Z { + N arr1[1]{ M{""} }; + N arr2[2]{ M{""}, M{""} }; + N arr1e[1] = { M{""} }; + N arr2e[2] = { M{""}, M{""} }; +} z; + +struct Y { + k name; + int j = 42; + int i = j; + operator M(); +}; + +struct W { + M arr1[1]{ Y{""} }; + M arr2[2]{ Y{""}, Y{""} }; + M arr3[3]{ Y{""}, Y{""}, Y{""} }; +} w; base-commit: 6dbf0d252f69ab2924256e6778ba7dc55d5b6915 -- 2.44.0