Hi!
On 2022-11-09T14:53:44+0100, Richard Biener via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
> On Wed, Oct 26, 2022 at 10:37 AM <arthur.co...@embecosm.com> wrote:
>> This patch [...] also contains a constant evaluator, ported
>> over from the C++ frontend.
Given that, and then:
>> --- /dev/null
>> +++ b/gcc/rust/backend/rust-constexpr.cc
>> +struct constexpr_global_ctx
>> +{
>> + HOST_WIDE_INT constexpr_ops_count;
>
> If this isn't a INTEGER_CST related value then please avoid HOST_WIDE_INT
> and instead use uint64_t (or other more appropriate types).
>
>> +
>> + constexpr_global_ctx () : constexpr_ops_count (0) {}
>> +};
>> +[...]
>> +static tree
>> +constexpr_expression (const constexpr_ctx *ctx, tree t)
>> +{
>> + [...]
>> + // Avoid excessively long constexpr evaluations
>> + if (++ctx->global->constexpr_ops_count >= constexpr_ops_limit)
>> + {
>> + rust_error_at (
>> + Location (loc),
>> + "%<constexpr%> evaluation operation count exceeds limit of "
>> + "%wd (use %<-fconstexpr-ops-limit=%> to increase the limit)",
>> + constexpr_ops_limit);
>> +
>> + return t;
>> + }
Arthur thus turned the 'HOST_WIDE_INT constexpr_ops_count' into an
'unsigned long', see <https://github.com/Rust-GCC/gccrs/pull/1661>
"58e75f65e56d: Remove HOST_WIDE_INT struct member", but that results in
GCC bootstrap failure:
[...]/source-gcc/gcc/rust/backend/rust-constexpr.cc: In function
‘tree_node* Rust::Compile::constexpr_expression(const constexpr_ctx*, tree)’:
[...]/source-gcc/gcc/rust/backend/rust-constexpr.cc:99:42: error:
comparison of integer expressions of different signedness: ‘long unsigned int’
and ‘long int’ [-Werror=sign-compare]
99 | if (++ctx->global->constexpr_ops_count >= constexpr_ops_limit)
See the original C++ code:
gcc/cp/constexpr.cc: HOST_WIDE_INT constexpr_ops_count;
gcc/c-family/c.opt-fconstexpr-ops-limit=
gcc/c-family/c.opt:C++ ObjC++ Joined RejectNegative Host_Wide_Int
Var(constexpr_ops_limit) Init(33554432)
gcc/c-family/c.opt--fconstexpr-ops-limit=<number> Specify maximum
number of constexpr operations during a single constexpr evaluation.
So I suggest change back the GCC/Rust 'constexpr_ops_count' to
'HOST_WIDE_INT' (submitted <https://github.com/Rust-GCC/gccrs/pull/1666>
'Revert #1661 "58e75f65e56d: Remove HOST_WIDE_INT struct member"'), and
if anything needs to be changed, do thatt in GCC/C++ first, and then
mirror that into GCC/Rust.
Grüße
Thomas
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