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| author | Jason Merrill <jason@redhat.com> | 2016-10-15 17:25:55 -0400 |
|---|---|---|
| committer | Jason Merrill <jason@gcc.gnu.org> | 2016-10-15 17:25:55 -0400 |
| commit | 68d01920587dc9424344514676f8000b4add9cd4 (patch) | |
| tree | c94ec9046c17252cbf66d9b7b135d8464b37c85c /gcc | |
| parent | f9e9d32f79409fd2f4d7bc73d3576a33fac9b715 (diff) | |
| download | gcc-68d01920587dc9424344514676f8000b4add9cd4.zip gcc-68d01920587dc9424344514676f8000b4add9cd4.tar.gz gcc-68d01920587dc9424344514676f8000b4add9cd4.tar.bz2 | |
PR c++/77945 - constexpr and trivial copy
* constexpr.c (maybe_simplify_trivial_copy): New.
(cxx_eval_store_expression): Call it.
* call.c (build_over_call): Use unsigned char for trivial copy.
From-SVN: r241204
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/cp/ChangeLog | 7 | ||||
| -rw-r--r-- | gcc/cp/call.c | 2 | ||||
| -rw-r--r-- | gcc/cp/constexpr.c | 23 | ||||
| -rw-r--r-- | gcc/testsuite/g++.dg/cpp0x/constexpr-trivial2.C | 14 |
4 files changed, 45 insertions, 1 deletions
diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog index 43c573b..54ffee8 100644 --- a/gcc/cp/ChangeLog +++ b/gcc/cp/ChangeLog @@ -1,3 +1,10 @@ +2016-10-15 Jason Merrill <jason@redhat.com> + + PR c++/77945 + * constexpr.c (maybe_simplify_trivial_copy): New. + (cxx_eval_store_expression): Call it. + * call.c (build_over_call): Use unsigned char for trivial copy. + 2016-10-14 Jason Merrill <jason@redhat.com> Implement P0017R1, C++17 aggregates with bases. diff --git a/gcc/cp/call.c b/gcc/cp/call.c index 4bee487..4c19d2f 100644 --- a/gcc/cp/call.c +++ b/gcc/cp/call.c @@ -7909,7 +7909,7 @@ build_over_call (struct z_candidate *cand, int flags, tsubst_flags_t complain) arg2 = TYPE_SIZE_UNIT (as_base); arg0 = cp_build_addr_expr (to, complain); - array_type = build_array_type (char_type_node, + array_type = build_array_type (unsigned_char_type_node, build_index_type (size_binop (MINUS_EXPR, arg2, size_int (1)))); diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c index f5235fc..3c4fcfa 100644 --- a/gcc/cp/constexpr.c +++ b/gcc/cp/constexpr.c @@ -3206,6 +3206,26 @@ var_in_maybe_constexpr_fn (tree t) return var_in_constexpr_fn (t); } +/* We're assigning INIT to TARGET. In do_build_copy_constructor and + build_over_call we implement trivial copy of a class with tail padding using + assignment of character arrays, which is valid in normal code, but not in + constexpr evaluation. We don't need to worry about clobbering tail padding + in constexpr evaluation, so strip the type punning. */ + +static void +maybe_simplify_trivial_copy (tree &target, tree &init) +{ + if (TREE_CODE (target) == MEM_REF + && TREE_CODE (init) == MEM_REF + && TREE_TYPE (target) == TREE_TYPE (init) + && TREE_CODE (TREE_TYPE (target)) == ARRAY_TYPE + && TREE_TYPE (TREE_TYPE (target)) == unsigned_char_type_node) + { + target = build_fold_indirect_ref (TREE_OPERAND (target, 0)); + init = build_fold_indirect_ref (TREE_OPERAND (init, 0)); + } +} + /* Evaluate an INIT_EXPR or MODIFY_EXPR. */ static tree @@ -3222,6 +3242,9 @@ cxx_eval_store_expression (const constexpr_ctx *ctx, tree t, /* First we figure out where we're storing to. */ tree target = TREE_OPERAND (t, 0); + + maybe_simplify_trivial_copy (target, init); + tree type = TREE_TYPE (target); target = cxx_eval_constant_expression (ctx, target, true, diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-trivial2.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-trivial2.C new file mode 100644 index 0000000..d241114 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-trivial2.C @@ -0,0 +1,14 @@ +// PR c++/77945 +// { dg-do compile { target c++11 } } + +struct T +{ + int x = 0; + bool y = 0; + constexpr T() {} +}; + +int main() +{ + constexpr T t = (T{} = T{}); +} |