Open
Description
Optimizations for format_args! can construct a &str constant longer than isize::MAX or even usize::MAX. I have observed this when cross-compiling to a 32-bit target from a 64-bit host. If compiled on a 32-bit host, rustc would probably panic in String resizing.
Setup
#![allow(internal_features)]
#![feature(core_intrinsics)]
use core::{fmt, intrinsics};
macro_rules! concat_repeat(
(16, $($x:literal)*) => { concat_repeat!(15, $($x)* $($x)*) };
(15, $($x:literal)*) => { concat_repeat!(14, $($x)* $($x)*) };
(14, $($x:literal)*) => { concat_repeat!(13, $($x)* $($x)*) };
(13, $($x:literal)*) => { concat_repeat!(12, $($x)* $($x)*) };
(12, $($x:literal)*) => { concat_repeat!(11, $($x)* $($x)*) };
(11, $($x:literal)*) => { concat_repeat!(10, $($x)* $($x)*) };
(10, $($x:literal)*) => { concat_repeat!(9, $($x)* $($x)*) };
(9, $($x:literal)*) => { concat_repeat!(8, $($x)* $($x)*) };
(8, $($x:literal)*) => { concat_repeat!(7, $($x)* $($x)*) };
(7, $($x:literal)*) => { concat_repeat!(6, $($x)* $($x)*) };
(6, $($x:literal)*) => { concat_repeat!(5, $($x)* $($x)*) };
(5, $($x:literal)*) => { concat_repeat!(4, $($x)* $($x)*) };
(4, $($x:literal)*) => { concat_repeat!(3, $($x)* $($x)*) };
(3, $($x:literal)*) => { concat_repeat!(2, $($x)* $($x)*) };
(2, $($x:literal)*) => { concat_repeat!(1, $($x)* $($x)*) };
(1, $($x:literal)*) => { concat!($($x),*, $($x),*) };
);
// fmt::Arguments::as_statically_known_str
#[inline]
fn as_statically_known_str(args: &fmt::Arguments<'_>) -> Option<&'static str> {
let s = args.as_str();
if intrinsics::is_val_statically_known(s.is_some()) {
s
} else {
None
}
}
fn print_len(args: fmt::Arguments<'_>) {
let s = as_statically_known_str(&args).expect("statically known");
println!("len = {}", s.len());
}isize::MAX overflow
This format_args! is optimized to a constant &str with length 2147483648 (i32::MAX + 1).
fn main() {
print_len(format_args!(
concat_repeat!(8, "{x}{x}{x}{x}{x}{x}{x}{x}"),
x = concat_repeat!(15, "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"),
));
}Compilation produces this error:
$ cargo build --release --target=i686-unknown-linux-gnu
error[E0080]: it is undefined behavior to use this value
--> src/main.rs:36:1
|
36 | fn main() {
| ^^^^^^^^^ constructing invalid value at .<deref>[0]: encountered invalid reference metadata: slice is bigger than largest supported object
|
= note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
= note: the raw bytes of the constant (size: 4, align: 4) {
╾─a6<imm>─╼ │ ╾──╼
}
note: erroneous constant encountered
--> src/main.rs:22:30
|
22 | (1, $($x:literal)*) => { concat!($($x),*, $($x),*) };
| ^^^^^^^^^^^^^^^^^^^^^^^^^
...
38 | concat_repeat!(8, "{x}{x}{x}{x}{x}{x}{x}{x}"),
| --------------------------------------------- in this macro invocation
|
= note: this note originates in the macro `concat` which comes from the expansion of the macro `concat_repeat` (in Nightly builds, run with -Z macro-backtrace for more info)
For more information about this error, try `rustc --explain E0080`.
error: could not compile `fmt-large-string` (bin "fmt-large-string") due to 1 previous error
usize::MAX overflow
This format_args! is optimized to a constant &str with length 4294967296 (1 << 32).
fn main() {
print_len(format_args!(
concat_repeat!(8, "{x}{x}{x}{x}{x}{x}{x}{x}"),
x = concat_repeat!(16, "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"),
));
}Compilation aborts with this ICE:
$ cargo build --release --target=i686-unknown-linux-gnu
thread 'rustc' panicked at /rustc/78948ac259253ce89effca1e8bb64d16f4684aa4/compiler/rustc_middle/src/mir/interpret/value.rs:139:32:
Box<dyn Any>
stack backtrace:
0: 0x117933967 - std::backtrace::Backtrace::create::he72e5c6ec1676771
1: 0x1179338b5 - std::backtrace::Backtrace::force_capture::h83527e80780e82cc
2: 0x11552e127 - std[e6c9211e353aebe9]::panicking::update_hook::<alloc[ec63ab7aac1f102d]::boxed::Box<rustc_driver_impl[8c05a4638ee6701e]::install_ice_hook::{closure#1}>>::{closure#0}
3: 0x11794fb23 - std::panicking::rust_panic_with_hook::h46cbd39e2fba8522
4: 0x1155c4ef7 - std[e6c9211e353aebe9]::panicking::begin_panic::<rustc_errors[3696162f341b2643]::ExplicitBug>::{closure#0}
5: 0x1155b0289 - std[e6c9211e353aebe9]::sys::backtrace::__rust_end_short_backtrace::<std[e6c9211e353aebe9]::panicking::begin_panic<rustc_errors[3696162f341b2643]::ExplicitBug>::{closure#0}, !>
6: 0x11ace515e - std[e6c9211e353aebe9]::panicking::begin_panic::<rustc_errors[3696162f341b2643]::ExplicitBug>
7: 0x11ace5716 - <rustc_errors[3696162f341b2643]::diagnostic::BugAbort as rustc_errors[3696162f341b2643]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
8: 0x11ad7322c - rustc_middle[a14ca4759a2c046f]::util::bug::opt_span_bug_fmt::<rustc_span[e538c9ec2b20cab]::span_encoding::Span>::{closure#0}
9: 0x1163c9217 - rustc_middle[a14ca4759a2c046f]::ty::context::tls::with_opt::<rustc_middle[a14ca4759a2c046f]::util::bug::opt_span_bug_fmt<rustc_span[e538c9ec2b20cab]::span_encoding::Span>::{closure#0}, !>::{closure#0}
10: 0x1163c8d25 - rustc_middle[a14ca4759a2c046f]::ty::context::tls::with_context_opt::<rustc_middle[a14ca4759a2c046f]::ty::context::tls::with_opt<rustc_middle[a14ca4759a2c046f]::util::bug::opt_span_bug_fmt<rustc_span[e538c9ec2b20cab]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
11: 0x11ad7310b - rustc_middle[a14ca4759a2c046f]::util::bug::bug_fmt
12: 0x11ad8a899 - <rustc_middle[a14ca4759a2c046f]::mir::interpret::value::Scalar<rustc_middle[a14ca4759a2c046f]::mir::interpret::AllocId>>::from_uint::<u128>::{closure#0}
13: 0x11662629c - <rustc_const_eval[7027bb1ad2ba1c5d]::interpret::operand::Immediate>::new_slice::<rustc_const_eval[7027bb1ad2ba1c5d]::interpret::eval_context::InterpCx<rustc_const_eval[7027bb1ad2ba1c5d]::const_eval::dummy_machine::DummyMachine>>
14: 0x11668f04e - <rustc_const_eval[7027bb1ad2ba1c5d]::interpret::eval_context::InterpCx<rustc_const_eval[7027bb1ad2ba1c5d]::const_eval::dummy_machine::DummyMachine>>::eval_mir_constant::{closure#0}
15: 0x1167c092e - <rustc_mir_transform[e6e01cd5aad92b91]::known_panics_lint::ConstPropagator>::eval_constant
16: 0x1167c17c9 - <rustc_mir_transform[e6e01cd5aad92b91]::known_panics_lint::ConstPropagator as rustc_middle[a14ca4759a2c046f]::mir::visit::Visitor>::visit_assign
17: 0x1167c7272 - <rustc_mir_transform[e6e01cd5aad92b91]::known_panics_lint::ConstPropagator as rustc_middle[a14ca4759a2c046f]::mir::visit::Visitor>::visit_basic_block_data
18: 0x1167c12b5 - <rustc_mir_transform[e6e01cd5aad92b91]::known_panics_lint::ConstPropagator as rustc_middle[a14ca4759a2c046f]::mir::visit::Visitor>::visit_body
19: 0x1167bdb0c - <rustc_mir_transform[e6e01cd5aad92b91]::known_panics_lint::KnownPanicsLint as rustc_mir_transform[e6e01cd5aad92b91]::pass_manager::MirLint>::run_lint
20: 0x116724e3e - rustc_mir_transform[e6e01cd5aad92b91]::pass_manager::run_passes_inner
21: 0x11674c2f8 - rustc_mir_transform[e6e01cd5aad92b91]::run_analysis_to_runtime_passes
22: 0x11674d32b - rustc_mir_transform[e6e01cd5aad92b91]::promoted_mir
23: 0x116ec6b36 - rustc_query_impl[4198737f17c2ba68]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[4198737f17c2ba68]::query_impl::promoted_mir::dynamic_query::{closure#2}::{closure#0}, rustc_middle[a14ca4759a2c046f]::query::erase::Erased<[u8; 8usize]>>
24: 0x116c65b59 - rustc_query_system[e1590dd222ee792c]::query::plumbing::try_execute_query::<rustc_query_impl[4198737f17c2ba68]::DynamicConfig<rustc_query_system[e1590dd222ee792c]::query::caches::DefIdCache<rustc_middle[a14ca4759a2c046f]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[4198737f17c2ba68]::plumbing::QueryCtxt, false>
25: 0x116ee4d74 - rustc_query_impl[4198737f17c2ba68]::query_impl::promoted_mir::get_query_non_incr::__rust_end_short_backtrace
26: 0x1154a4550 - rustc_const_eval[7027bb1ad2ba1c5d]::const_eval::eval_queries::eval_to_allocation_raw_provider
27: 0x116ec976c - rustc_query_impl[4198737f17c2ba68]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[4198737f17c2ba68]::query_impl::eval_to_allocation_raw::dynamic_query::{closure#2}::{closure#0}, rustc_middle[a14ca4759a2c046f]::query::erase::Erased<[u8; 24usize]>>
28: 0x116e7aa5e - <rustc_query_impl[4198737f17c2ba68]::query_impl::eval_to_allocation_raw::dynamic_query::{closure#2} as core[c2a971250a84775]::ops::function::FnOnce<(rustc_middle[a14ca4759a2c046f]::ty::context::TyCtxt, rustc_middle[a14ca4759a2c046f]::ty::PseudoCanonicalInput<rustc_middle[a14ca4759a2c046f]::mir::interpret::GlobalId>)>>::call_once
29: 0x116c9de27 - rustc_query_system[e1590dd222ee792c]::query::plumbing::try_execute_query::<rustc_query_impl[4198737f17c2ba68]::DynamicConfig<rustc_query_system[e1590dd222ee792c]::query::caches::DefaultCache<rustc_middle[a14ca4759a2c046f]::ty::PseudoCanonicalInput<rustc_middle[a14ca4759a2c046f]::mir::interpret::GlobalId>, rustc_middle[a14ca4759a2c046f]::query::erase::Erased<[u8; 24usize]>>, false, false, false>, rustc_query_impl[4198737f17c2ba68]::plumbing::QueryCtxt, false>
30: 0x116f06130 - rustc_query_impl[4198737f17c2ba68]::query_impl::eval_to_allocation_raw::get_query_non_incr::__rust_end_short_backtrace
31: 0x1154a02cc - rustc_const_eval[7027bb1ad2ba1c5d]::const_eval::eval_queries::eval_to_const_value_raw_provider
32: 0x116ec9f3c - rustc_query_impl[4198737f17c2ba68]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[4198737f17c2ba68]::query_impl::eval_to_const_value_raw::dynamic_query::{closure#2}::{closure#0}, rustc_middle[a14ca4759a2c046f]::query::erase::Erased<[u8; 24usize]>>
33: 0x116e8004e - <rustc_query_impl[4198737f17c2ba68]::query_impl::eval_to_const_value_raw::dynamic_query::{closure#2} as core[c2a971250a84775]::ops::function::FnOnce<(rustc_middle[a14ca4759a2c046f]::ty::context::TyCtxt, rustc_middle[a14ca4759a2c046f]::ty::PseudoCanonicalInput<rustc_middle[a14ca4759a2c046f]::mir::interpret::GlobalId>)>>::call_once
34: 0x116ca0702 - rustc_query_system[e1590dd222ee792c]::query::plumbing::try_execute_query::<rustc_query_impl[4198737f17c2ba68]::DynamicConfig<rustc_query_system[e1590dd222ee792c]::query::caches::DefaultCache<rustc_middle[a14ca4759a2c046f]::ty::PseudoCanonicalInput<rustc_middle[a14ca4759a2c046f]::mir::interpret::GlobalId>, rustc_middle[a14ca4759a2c046f]::query::erase::Erased<[u8; 24usize]>>, false, true, false>, rustc_query_impl[4198737f17c2ba68]::plumbing::QueryCtxt, false>
35: 0x116f06cf0 - rustc_query_impl[4198737f17c2ba68]::query_impl::eval_to_const_value_raw::get_query_non_incr::__rust_end_short_backtrace
36: 0x116439c1d - <rustc_middle[a14ca4759a2c046f]::ty::context::TyCtxt>::const_eval_global_id
37: 0x116439057 - <rustc_middle[a14ca4759a2c046f]::ty::context::TyCtxt>::const_eval_resolve
38: 0x11668ed1c - <rustc_const_eval[7027bb1ad2ba1c5d]::interpret::eval_context::InterpCx<rustc_const_eval[7027bb1ad2ba1c5d]::const_eval::dummy_machine::DummyMachine>>::eval_mir_constant::{closure#0}
39: 0x1167c092e - <rustc_mir_transform[e6e01cd5aad92b91]::known_panics_lint::ConstPropagator>::eval_constant
40: 0x1167c1ab6 - <rustc_mir_transform[e6e01cd5aad92b91]::known_panics_lint::ConstPropagator as rustc_middle[a14ca4759a2c046f]::mir::visit::Visitor>::visit_assign
41: 0x1167c7272 - <rustc_mir_transform[e6e01cd5aad92b91]::known_panics_lint::ConstPropagator as rustc_middle[a14ca4759a2c046f]::mir::visit::Visitor>::visit_basic_block_data
42: 0x1167c12b5 - <rustc_mir_transform[e6e01cd5aad92b91]::known_panics_lint::ConstPropagator as rustc_middle[a14ca4759a2c046f]::mir::visit::Visitor>::visit_body
43: 0x1167bdb0c - <rustc_mir_transform[e6e01cd5aad92b91]::known_panics_lint::KnownPanicsLint as rustc_mir_transform[e6e01cd5aad92b91]::pass_manager::MirLint>::run_lint
44: 0x116724e3e - rustc_mir_transform[e6e01cd5aad92b91]::pass_manager::run_passes_inner
45: 0x11674c2f8 - rustc_mir_transform[e6e01cd5aad92b91]::run_analysis_to_runtime_passes
46: 0x11674bf0c - rustc_mir_transform[e6e01cd5aad92b91]::mir_drops_elaborated_and_const_checked
47: 0x116ecb23a - rustc_query_impl[4198737f17c2ba68]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[4198737f17c2ba68]::query_impl::mir_drops_elaborated_and_const_checked::dynamic_query::{closure#2}::{closure#0}, rustc_middle[a14ca4759a2c046f]::query::erase::Erased<[u8; 8usize]>>
48: 0x116cf5610 - rustc_query_system[e1590dd222ee792c]::query::plumbing::try_execute_query::<rustc_query_impl[4198737f17c2ba68]::DynamicConfig<rustc_data_structures[be3606a25063c5fa]::vec_cache::VecCache<rustc_hir[d33cae78527aecc7]::hir_id::OwnerId, rustc_middle[a14ca4759a2c046f]::query::erase::Erased<[u8; 8usize]>, rustc_query_system[e1590dd222ee792c]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[4198737f17c2ba68]::plumbing::QueryCtxt, false>
49: 0x116ee14f8 - rustc_query_impl[4198737f17c2ba68]::query_impl::mir_drops_elaborated_and_const_checked::get_query_non_incr::__rust_end_short_backtrace
50: 0x115f05b76 - <rustc_middle[a14ca4759a2c046f]::ty::context::TyCtxt>::par_hir_body_owners::<rustc_interface[f99dd79e9a35495f]::passes::run_required_analyses::{closure#3}::{closure#0}>::{closure#0}
51: 0x115fa978b - rustc_interface[f99dd79e9a35495f]::passes::run_required_analyses
52: 0x115fabae3 - rustc_interface[f99dd79e9a35495f]::passes::analysis
53: 0x116ecb6ea - rustc_query_impl[4198737f17c2ba68]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[4198737f17c2ba68]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[a14ca4759a2c046f]::query::erase::Erased<[u8; 0usize]>>
54: 0x116c69d54 - rustc_query_system[e1590dd222ee792c]::query::plumbing::try_execute_query::<rustc_query_impl[4198737f17c2ba68]::DynamicConfig<rustc_query_system[e1590dd222ee792c]::query::caches::SingleCache<rustc_middle[a14ca4759a2c046f]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[4198737f17c2ba68]::plumbing::QueryCtxt, false>
55: 0x116ed75b5 - rustc_query_impl[4198737f17c2ba68]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
56: 0x11551eb78 - rustc_interface[f99dd79e9a35495f]::passes::create_and_enter_global_ctxt::<core[c2a971250a84775]::option::Option<rustc_interface[f99dd79e9a35495f]::queries::Linker>, rustc_driver_impl[8c05a4638ee6701e]::run_compiler::{closure#0}::{closure#2}>
57: 0x115534479 - rustc_interface[f99dd79e9a35495f]::interface::run_compiler::<(), rustc_driver_impl[8c05a4638ee6701e]::run_compiler::{closure#0}>::{closure#1}
58: 0x11551fe3d - std[e6c9211e353aebe9]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[f99dd79e9a35495f]::util::run_in_thread_with_globals<rustc_interface[f99dd79e9a35495f]::util::run_in_thread_pool_with_globals<rustc_interface[f99dd79e9a35495f]::interface::run_compiler<(), rustc_driver_impl[8c05a4638ee6701e]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
59: 0x115539fcd - <<std[e6c9211e353aebe9]::thread::Builder>::spawn_unchecked_<rustc_interface[f99dd79e9a35495f]::util::run_in_thread_with_globals<rustc_interface[f99dd79e9a35495f]::util::run_in_thread_pool_with_globals<rustc_interface[f99dd79e9a35495f]::interface::run_compiler<(), rustc_driver_impl[8c05a4638ee6701e]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[c2a971250a84775]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
60: 0x117956d4b - std::sys::pal::unix::thread::Thread::new::thread_start::h84c0937bf04c1f94
61: 0x7ff8030cd253 - __pthread_start
rustc version: 1.87.0-nightly (78948ac25 2025-03-20)
platform: x86_64-apple-darwin
query stack during panic:
#0 [promoted_mir] optimizing promoted MIR for `main`
#1 [eval_to_allocation_raw] const-evaluating + checking `main::promoted[1]`
#2 [eval_to_const_value_raw] simplifying constant for the type system `main::promoted[1]`
#3 [mir_drops_elaborated_and_const_checked] elaborating drops for `main`
#4 [analysis] running analysis passes on this crate
end of query stack