Message ID | ZfB7NHoYci59QEAZ@redhat.com |
---|---|
State | New |
Headers | show |
Series | [v2] c++: ICE with temporary of class type in array DMI [PR109966] | expand |
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? Jason
diff --git a/gcc/cp/typeck2.cc b/gcc/cp/typeck2.cc index 31198b2f9f5..21d4f42ae20 100644 --- a/gcc/cp/typeck2.cc +++ b/gcc/cp/typeck2.cc @@ -1406,6 +1406,7 @@ 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 @@ -1414,24 +1415,33 @@ digest_init_flags (tree type, tree init, int flags, tsubst_flags_t complain) static bool potential_prvalue_result_of (tree subob, tree full_expr) { +#define RECUR(t) potential_prvalue_result_of (subob, t) 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 + && can_convert (strip_array_types (TREE_TYPE (full_expr)), + TREE_TYPE (subob), tf_none)) + return true; + return false; +#undef RECUR } /* Callback to replace PLACEHOLDER_EXPRs in a TARGET_EXPR (which isn't used 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;