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Correct outdated object size limit #127546

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merged 8 commits into from
Sep 21, 2024
Merged

Correct outdated object size limit #127546

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42dbf29
Correct outdated object size limit
workingjubilee Jul 10, 2024
d6383b4
bless issue-56762.rs as huge-static.rs
workingjubilee Jul 10, 2024
f4cb6ef
Keep object-size-dependent tests failing
workingjubilee Jul 10, 2024
65f132f
Bless rustc_abi::obj_size_bound tests
workingjubilee Jul 10, 2024
28628f3
Normalize being an annoying little compile test
workingjubilee Sep 19, 2024
325af25
TL note: current means target
workingjubilee Sep 20, 2024
d93d2f1
miri: An error message got changed
workingjubilee Sep 20, 2024
cf78f26
compiler: Precisely name units of object size
workingjubilee Sep 21, 2024
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10 changes: 4 additions & 6 deletions compiler/rustc_abi/src/lib.rs
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Expand Up @@ -337,23 +337,21 @@ impl TargetDataLayout {
Ok(dl)
}

/// Returns exclusive upper bound on object size.
/// Returns **exclusive** upper bound on object size.
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///
/// The theoretical maximum object size is defined as the maximum positive `isize` value.
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I am not entirely sure what is even meant by "object". In general we are saying that "allocated objects" are limited by isize::MAX, and we do not publicly document anything else even for 64bit targets. So we do currently allow people to create heap allocations larger than obj_size_bound, and we rely on LLVM supporting that. It is only Rust types that can't be any bigger, and therefore static and let-bound variables and Box.

So either we should clarify the comment to say that this does not apply to all heap allocations, or we need to fix our docs.

@nikic will LLVM miscompile things if a heap allocation gets bigger than 2^61 bytes because that overflows u64 when counting in bits? Or does the 2^64 bits limit only apply to LLVM "typed objects"? Or is this too theoretical because nothing can be that big anyway? ;)

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I think it would only be a problem if it's a typed allocation/access, but I'm not particularly confident in that :)

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anyone got a 64-bit address space computer lying around to find out?

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I am not entirely sure what is even meant by "object".

Honestly I'm also not completely confident... I think allocation is what is meant?

I was pretty much just rolling with it because "we have a slightly wibbly definition of 'object' deep in the codegen backend" feels kinda low on our list of concerns. Relatively speaking.

/// This ensures that the `offset` semantics remain well-defined by allowing it to correctly
/// index every address within an object along with one byte past the end, along with allowing
/// `isize` to store the difference between any two pointers into an object.
///
/// The upper bound on 64-bit currently needs to be lower because LLVM uses a 64-bit integer
/// to represent object size in bits. It would need to be 1 << 61 to account for this, but is
/// currently conservatively bounded to 1 << 47 as that is enough to cover the current usable
/// address space on 64-bit ARMv8 and x86_64.
/// LLVM uses a 64-bit integer to represent object size in bits, but we care only for bytes,
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/// so we adopt such a more-constrained address space due to its technical limitations.
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#[inline]
pub fn obj_size_bound(&self) -> u64 {
match self.pointer_size.bits() {
16 => 1 << 15,
32 => 1 << 31,
64 => 1 << 47,
64 => 1 << 61,
bits => panic!("obj_size_bound: unknown pointer bit size {bits}"),
}
}
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2 changes: 1 addition & 1 deletion compiler/rustc_hir_analysis/messages.ftl
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Expand Up @@ -497,7 +497,7 @@ hir_analysis_tait_forward_compat2 = item does not constrain `{$opaque_type}`, bu

hir_analysis_target_feature_on_main = `main` function is not allowed to have `#[target_feature]`

hir_analysis_too_large_static = extern static is too large for the current architecture
hir_analysis_too_large_static = extern static is too large for the target architecture

hir_analysis_track_caller_on_main = `main` function is not allowed to be `#[track_caller]`
.suggestion = remove this annotation
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_hir_typeck/src/intrinsicck.rs
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Expand Up @@ -95,7 +95,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
format!("{v} bits")
} else {
// `u128` should definitely be able to hold the size of different architectures
// larger sizes should be reported as error `are too big for the current architecture`
// larger sizes should be reported as error `are too big for the target architecture`
// otherwise we have a bug somewhere
bug!("{:?} overflow for u128", size)
}
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2 changes: 1 addition & 1 deletion compiler/rustc_middle/messages.ftl
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Expand Up @@ -103,5 +103,5 @@ middle_unknown_layout =
the type `{$ty}` has an unknown layout

middle_values_too_big =
values of the type `{$ty}` are too big for the current architecture
values of the type `{$ty}` are too big for the target architecture
middle_written_to_path = the full type name has been written to '{$path}'
2 changes: 1 addition & 1 deletion compiler/rustc_middle/src/ty/layout.rs
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Expand Up @@ -264,7 +264,7 @@ impl<'tcx> fmt::Display for LayoutError<'tcx> {
match *self {
LayoutError::Unknown(ty) => write!(f, "the type `{ty}` has an unknown layout"),
LayoutError::SizeOverflow(ty) => {
write!(f, "values of the type `{ty}` are too big for the current architecture")
write!(f, "values of the type `{ty}` are too big for the target architecture")
}
LayoutError::NormalizationFailure(t, e) => write!(
f,
Expand Down
4 changes: 2 additions & 2 deletions compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs
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Expand Up @@ -2269,12 +2269,12 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
}
rustc_transmute::Reason::SrcSizeOverflow => {
format!(
"values of the type `{src}` are too big for the current architecture"
"values of the type `{src}` are too big for the target architecture"
)
}
rustc_transmute::Reason::DstSizeOverflow => {
format!(
"values of the type `{dst}` are too big for the current architecture"
"values of the type `{dst}` are too big for the target architecture"
)
}
rustc_transmute::Reason::DstHasStricterAlignment {
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4 changes: 2 additions & 2 deletions src/tools/miri/tests/fail/type-too-large.stderr
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@@ -1,8 +1,8 @@
error: post-monomorphization error: values of the type `[u8; 2305843011361177600]` are too big for the current architecture
error: post-monomorphization error: values of the type `[u8; 2305843011361177600]` are too big for the target architecture
--> tests/fail/type-too-large.rs:LL:CC
|
LL | _fat = [0; (1u64 << 61) as usize + (1u64 << 31) as usize];
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ values of the type `[u8; 2305843011361177600]` are too big for the current architecture
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ values of the type `[u8; 2305843011361177600]` are too big for the target architecture
|
= note: BACKTRACE:
= note: inside `main` at tests/fail/type-too-large.rs:LL:CC
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2 changes: 0 additions & 2 deletions src/tools/tidy/src/issues.txt
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Expand Up @@ -552,7 +552,6 @@ ui/const-generics/infer/issue-77092.rs
ui/const-generics/issue-102124.rs
ui/const-generics/issue-105689.rs
ui/const-generics/issue-106419-struct-with-multiple-const-params.rs
ui/const-generics/issue-112505-overflow.rs
ui/const-generics/issue-46511.rs
ui/const-generics/issue-66451.rs
ui/const-generics/issue-70408.rs
Expand Down Expand Up @@ -2718,7 +2717,6 @@ ui/limits/issue-15919-32.rs
ui/limits/issue-15919-64.rs
ui/limits/issue-17913.rs
ui/limits/issue-55878.rs
ui/limits/issue-56762.rs
ui/limits/issue-69485-var-size-diffs-too-large.rs
ui/limits/issue-75158-64.rs
ui/linkage-attr/auxiliary/issue-12133-dylib.rs
Expand Down
2 changes: 1 addition & 1 deletion tests/crashes/125476.rs
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@@ -1,4 +1,4 @@
//@ known-bug: rust-lang/rust#125476
//@ only-x86_64
pub struct Data([u8; usize::MAX >> 16]);
pub struct Data([u8; usize::MAX >> 2]);
const _: &'static [Data] = &[];
7 changes: 0 additions & 7 deletions tests/ui/const-generics/issue-112505-overflow.rs
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This file was deleted.

12 changes: 0 additions & 12 deletions tests/ui/const-generics/issue-112505-overflow.stderr
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This file was deleted.

10 changes: 10 additions & 0 deletions tests/ui/const-generics/transmute-fail.rs
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@@ -1,3 +1,8 @@
// ignore-tidy-linelength
//@ normalize-stderr-32bit: "values of the type `[^`]+` are too big" -> "values of the type $$REALLY_TOO_BIG are too big"
//@ normalize-stderr-64bit: "values of the type `[^`]+` are too big" -> "values of the type $$REALLY_TOO_BIG are too big"


#![feature(transmute_generic_consts)]
#![feature(generic_const_exprs)]
#![allow(incomplete_features)]
Expand Down Expand Up @@ -31,6 +36,11 @@ fn overflow(v: [[[u32; 8888888]; 9999999]; 777777777]) -> [[[u32; 9999999]; 7777
}
}

fn overflow_more(v: [[[u32; 8888888]; 9999999]; 777777777]) -> [[[u32; 9999999]; 777777777]; 239] {
unsafe { std::mem::transmute(v) } //~ ERROR cannot transmute between types of different sizes
}


fn transpose<const W: usize, const H: usize>(v: [[u32; H]; W]) -> [[u32; W]; H] {
unsafe {
std::mem::transmute(v)
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43 changes: 26 additions & 17 deletions tests/ui/const-generics/transmute-fail.stderr
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@@ -1,11 +1,11 @@
error: the constant `W` is not of type `usize`
--> $DIR/transmute-fail.rs:12:42
--> $DIR/transmute-fail.rs:17:42
|
LL | fn bar<const W: bool, const H: usize>(v: [[u32; H]; W]) -> [[u32; W]; H] {
| ^^^^^^^^^^^^^ expected `usize`, found `bool`

error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
--> $DIR/transmute-fail.rs:7:9
--> $DIR/transmute-fail.rs:12:9
|
LL | std::mem::transmute(v)
| ^^^^^^^^^^^^^^^^^^^
Expand All @@ -14,13 +14,13 @@ LL | std::mem::transmute(v)
= note: target type: `[[u32; W + 1]; H]` (size can vary because of [u32; W + 1])

error: the constant `W` is not of type `usize`
--> $DIR/transmute-fail.rs:15:9
--> $DIR/transmute-fail.rs:20:9
|
LL | std::mem::transmute(v)
| ^^^^^^^^^^^^^^^^^^^ expected `usize`, found `bool`

error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
--> $DIR/transmute-fail.rs:22:9
--> $DIR/transmute-fail.rs:27:9
|
LL | std::mem::transmute(v)
| ^^^^^^^^^^^^^^^^^^^
Expand All @@ -29,16 +29,25 @@ LL | std::mem::transmute(v)
= note: target type: `[u32; W * H * H]` (this type does not have a fixed size)

error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
--> $DIR/transmute-fail.rs:29:9
--> $DIR/transmute-fail.rs:34:9
|
LL | std::mem::transmute(v)
| ^^^^^^^^^^^^^^^^^^^
|
= note: source type: `[[[u32; 8888888]; 9999999]; 777777777]` (values of the type `[[u32; 8888888]; 9999999]` are too big for the current architecture)
= note: target type: `[[[u32; 9999999]; 777777777]; 8888888]` (values of the type `[[u32; 9999999]; 777777777]` are too big for the current architecture)
= note: source type: `[[[u32; 8888888]; 9999999]; 777777777]` (values of the type $REALLY_TOO_BIG are too big for the target architecture)
= note: target type: `[[[u32; 9999999]; 777777777]; 8888888]` (values of the type $REALLY_TOO_BIG are too big for the target architecture)

error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
--> $DIR/transmute-fail.rs:36:9
--> $DIR/transmute-fail.rs:40:14
|
LL | unsafe { std::mem::transmute(v) }
| ^^^^^^^^^^^^^^^^^^^
|
= note: source type: `[[[u32; 8888888]; 9999999]; 777777777]` (values of the type $REALLY_TOO_BIG are too big for the target architecture)
= note: target type: `[[[u32; 9999999]; 777777777]; 239]` (values of the type $REALLY_TOO_BIG are too big for the target architecture)

error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
--> $DIR/transmute-fail.rs:46:9
|
LL | std::mem::transmute(v)
| ^^^^^^^^^^^^^^^^^^^
Expand All @@ -47,7 +56,7 @@ LL | std::mem::transmute(v)
= note: target type: `[[u32; W]; H]` (size can vary because of [u32; W])

error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
--> $DIR/transmute-fail.rs:47:9
--> $DIR/transmute-fail.rs:57:9
|
LL | std::mem::transmute(v)
| ^^^^^^^^^^^^^^^^^^^
Expand All @@ -56,7 +65,7 @@ LL | std::mem::transmute(v)
= note: target type: `[u32; W * H]` (this type does not have a fixed size)

error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
--> $DIR/transmute-fail.rs:54:9
--> $DIR/transmute-fail.rs:64:9
|
LL | std::mem::transmute(v)
| ^^^^^^^^^^^^^^^^^^^
Expand All @@ -65,7 +74,7 @@ LL | std::mem::transmute(v)
= note: target type: `[[u32; W]; H]` (size can vary because of [u32; W])

error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
--> $DIR/transmute-fail.rs:63:9
--> $DIR/transmute-fail.rs:73:9
|
LL | std::mem::transmute(v)
| ^^^^^^^^^^^^^^^^^^^
Expand All @@ -74,7 +83,7 @@ LL | std::mem::transmute(v)
= note: target type: `[u32; D * W * H]` (this type does not have a fixed size)

error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
--> $DIR/transmute-fail.rs:72:9
--> $DIR/transmute-fail.rs:82:9
|
LL | std::mem::transmute(v)
| ^^^^^^^^^^^^^^^^^^^
Expand All @@ -83,7 +92,7 @@ LL | std::mem::transmute(v)
= note: target type: `[[u32; D * W]; H]` (size can vary because of [u32; D * W])

error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
--> $DIR/transmute-fail.rs:79:9
--> $DIR/transmute-fail.rs:89:9
|
LL | std::mem::transmute(v)
| ^^^^^^^^^^^^^^^^^^^
Expand All @@ -92,7 +101,7 @@ LL | std::mem::transmute(v)
= note: target type: `[u8; L * 2]` (this type does not have a fixed size)

error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
--> $DIR/transmute-fail.rs:86:9
--> $DIR/transmute-fail.rs:96:9
|
LL | std::mem::transmute(v)
| ^^^^^^^^^^^^^^^^^^^
Expand All @@ -101,7 +110,7 @@ LL | std::mem::transmute(v)
= note: target type: `[u16; L]` (this type does not have a fixed size)

error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
--> $DIR/transmute-fail.rs:93:9
--> $DIR/transmute-fail.rs:103:9
|
LL | std::mem::transmute(v)
| ^^^^^^^^^^^^^^^^^^^
Expand All @@ -110,14 +119,14 @@ LL | std::mem::transmute(v)
= note: target type: `[[u8; 1]; L]` (this type does not have a fixed size)

error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
--> $DIR/transmute-fail.rs:102:9
--> $DIR/transmute-fail.rs:112:9
|
LL | std::mem::transmute(v)
| ^^^^^^^^^^^^^^^^^^^
|
= note: source type: `[[u32; 2 * H]; W + W]` (size can vary because of [u32; 2 * H])
= note: target type: `[[u32; W + W]; 2 * H]` (size can vary because of [u32; W + W])

error: aborting due to 14 previous errors
error: aborting due to 15 previous errors

For more information about this error, try `rustc --explain E0512`.
2 changes: 1 addition & 1 deletion tests/ui/debuginfo/debuginfo-type-name-layout-ice-94961-1.rs
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Expand Up @@ -3,7 +3,7 @@

//@ compile-flags:-C debuginfo=2
//@ build-fail
//@ error-pattern: too big for the current architecture
//@ error-pattern: too big for the target architecture
//@ normalize-stderr-64bit: "18446744073709551615" -> "SIZE"
//@ normalize-stderr-32bit: "4294967295" -> "SIZE"

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2 changes: 1 addition & 1 deletion tests/ui/debuginfo/debuginfo-type-name-layout-ice-94961-1.stderr
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@@ -1,4 +1,4 @@
error: values of the type `[u8; usize::MAX]` are too big for the current architecture
error: values of the type `[u8; usize::MAX]` are too big for the target architecture

error: aborting due to 1 previous error

2 changes: 1 addition & 1 deletion tests/ui/debuginfo/debuginfo-type-name-layout-ice-94961-2.rs
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Expand Up @@ -5,7 +5,7 @@

//@ compile-flags:-C debuginfo=2
//@ build-fail
//@ error-pattern: too big for the current architecture
//@ error-pattern: too big for the target architecture
//@ normalize-stderr-64bit: "18446744073709551615" -> "SIZE"
//@ normalize-stderr-32bit: "4294967295" -> "SIZE"

Expand Down
2 changes: 1 addition & 1 deletion tests/ui/debuginfo/debuginfo-type-name-layout-ice-94961-2.stderr
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@@ -1,4 +1,4 @@
error: values of the type `[u8; usize::MAX]` are too big for the current architecture
error: values of the type `[u8; usize::MAX]` are too big for the target architecture

error: aborting due to 1 previous error

30 changes: 6 additions & 24 deletions tests/ui/extern/extern-static-size-overflow.rs
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Expand Up @@ -4,31 +4,13 @@ struct ReallyBig {
}

// The limit for "too big for the current architecture" is dependent on the target pointer size
// however it's artificially limited on 64 bits
// logic copied from rustc_target::abi::TargetDataLayout::obj_size_bound()
// but is artificially limited due to LLVM's internal architecture
// logic based on rustc_target::abi::TargetDataLayout::obj_size_bound()
const fn max_size() -> usize {
#[cfg(target_pointer_width = "16")]
{
1 << 15
}

#[cfg(target_pointer_width = "32")]
{
1 << 31
}

#[cfg(target_pointer_width = "64")]
{
1 << 47
}

#[cfg(not(any(
target_pointer_width = "16",
target_pointer_width = "32",
target_pointer_width = "64"
)))]
{
isize::MAX as usize
if usize::BITS < 61 {
1 << (usize::BITS - 1)
} else {
1 << 61
}
}

Expand Down
12 changes: 6 additions & 6 deletions tests/ui/extern/extern-static-size-overflow.stderr
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@@ -1,17 +1,17 @@
error: extern static is too large for the current architecture
--> $DIR/extern-static-size-overflow.rs:38:5
error: extern static is too large for the target architecture
--> $DIR/extern-static-size-overflow.rs:20:5
|
LL | static BAZ: [u8; max_size()];
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: extern static is too large for the current architecture
--> $DIR/extern-static-size-overflow.rs:39:5
error: extern static is too large for the target architecture
--> $DIR/extern-static-size-overflow.rs:21:5
|
LL | static UWU: [usize; usize::MAX];
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: extern static is too large for the current architecture
--> $DIR/extern-static-size-overflow.rs:40:5
error: extern static is too large for the target architecture
--> $DIR/extern-static-size-overflow.rs:22:5
|
LL | static A: ReallyBig;
| ^^^^^^^^^^^^^^^^^^^
Expand Down
2 changes: 1 addition & 1 deletion tests/ui/layout/size-of-val-raw-too-big.rs
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@@ -1,7 +1,7 @@
//@ build-fail
//@ compile-flags: --crate-type lib
//@ only-32bit Layout computation rejects this layout for different reasons on 64-bit.
//@ error-pattern: too big for the current architecture
//@ error-pattern: too big for the target architecture
#![feature(core_intrinsics)]
#![allow(internal_features)]

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2 changes: 1 addition & 1 deletion tests/ui/layout/size-of-val-raw-too-big.stderr
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@@ -1,4 +1,4 @@
error: values of the type `Example` are too big for the current architecture
error: values of the type `Example` are too big for the target architecture

error: aborting due to 1 previous error

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