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| author | Patrick Palka <ppalka@redhat.com> | 2020-08-05 15:05:30 -0400 |
|---|---|---|
| committer | Patrick Palka <ppalka@redhat.com> | 2020-08-05 15:05:30 -0400 |
| commit | d21252de6c81ed236d8981d47b9a57dc4f1c6d57 (patch) | |
| tree | 0998a63ef34180ce3fc314ad61f148431bd120b9 /gcc/cp/constexpr.c | |
| parent | dd30d93f1a3ead7b814c1b179cf7197e4bf1e183 (diff) | |
| download | gcc-d21252de6c81ed236d8981d47b9a57dc4f1c6d57.zip gcc-d21252de6c81ed236d8981d47b9a57dc4f1c6d57.tar.gz gcc-d21252de6c81ed236d8981d47b9a57dc4f1c6d57.tar.bz2 | |
c++: cxx_eval_vec_init after zero-initialization [PR96282]
In the first testcase below, expand_aggr_init_1 sets up t's default
constructor such that the ctor first zero-initializes the entire base b,
followed by calling b's default constructor, the latter of which just
default-initializes the array member b::m via a VEC_INIT_EXPR.
So upon constexpr evaluation of this latter VEC_INIT_EXPR, ctx->ctor is
nonempty due to the prior zero-initialization, and we proceed in
cxx_eval_vec_init to append new constructor_elts to the end of ctx->ctor
without first checking if a matching constructor_elt already exists.
This leads to ctx->ctor having two matching constructor_elts for each
index.
This patch fixes this issue by truncating a zero-initialized array
CONSTRUCTOR in cxx_eval_vec_init_1 before we begin appending array
elements to it. We propagate its zeroed out state during evaluation by
clearing CONSTRUCTOR_NO_CLEARING on each new appended aggregate element.
gcc/cp/ChangeLog:
PR c++/96282
* constexpr.c (cxx_eval_vec_init_1): Truncate ctx->ctor and
then clear CONSTRUCTOR_NO_CLEARING on each appended element
initializer if we're initializing a previously zero-initialized
array object.
gcc/testsuite/ChangeLog:
PR c++/96282
* g++.dg/cpp0x/constexpr-array26.C: New test.
* g++.dg/cpp0x/constexpr-array27.C: New test.
* g++.dg/cpp2a/constexpr-init18.C: New test.
Co-authored-by: Jason Merrill <jason@redhat.com>
Diffstat (limited to 'gcc/cp/constexpr.c')
| -rw-r--r-- | gcc/cp/constexpr.c | 18 |
1 files changed, 17 insertions, 1 deletions
diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c index b1c1d24..ab747a5 100644 --- a/gcc/cp/constexpr.c +++ b/gcc/cp/constexpr.c @@ -4171,6 +4171,18 @@ cxx_eval_vec_init_1 (const constexpr_ctx *ctx, tree atype, tree init, pre_init = true; } + bool zeroed_out = false; + if (!CONSTRUCTOR_NO_CLEARING (ctx->ctor)) + { + /* We're initializing an array object that had been zero-initialized + earlier. Truncate ctx->ctor, and propagate its zeroed state by + clearing CONSTRUCTOR_NO_CLEARING on each of the aggregate element + initializers we append to it. */ + gcc_checking_assert (initializer_zerop (ctx->ctor)); + zeroed_out = true; + vec_safe_truncate (*p, 0); + } + tree nelts = get_array_or_vector_nelts (ctx, atype, non_constant_p, overflow_p); unsigned HOST_WIDE_INT max = tree_to_uhwi (nelts); @@ -4182,7 +4194,11 @@ cxx_eval_vec_init_1 (const constexpr_ctx *ctx, tree atype, tree init, constexpr_ctx new_ctx; init_subob_ctx (ctx, new_ctx, idx, pre_init ? init : elttype); if (new_ctx.ctor != ctx->ctor) - CONSTRUCTOR_APPEND_ELT (*p, idx, new_ctx.ctor); + { + if (zeroed_out) + CONSTRUCTOR_NO_CLEARING (new_ctx.ctor) = false; + CONSTRUCTOR_APPEND_ELT (*p, idx, new_ctx.ctor); + } if (TREE_CODE (elttype) == ARRAY_TYPE) { /* A multidimensional array; recurse. */ |