Stream: git-wasmtime

Topic: wasmtime / issue #11086 When a component panics, the subs...

Wasmtime GitHub notifications bot (Jun 20 2025 at 10:02):

xiaocq2001 opened issue #11086:

Steps to Reproduce

• first, modify examples/component/wasm/guest.rs to generate panic in some cases, let's say generate panic when input is over 100.0
• second, modify examples/component/main.rs to invoke the guest function several times and print the result directly, e.g., use these values: 0.0, 32.0, 100.0, 100.1, 31.0, 50.0.
• Check output to see function call fails

Expected Results

Just value >100 panics and since panic is catched by trap, I expect the subsequent component calls recover to normal state.

Actual Results

Component calls after the panic keep failing, returning "wasm trap: cannot enter component instance"

Versions and Environment

Wasmtime version or commit: cfe17cb1c61658a157e7ad9da2ecbe5f314a2536

Operating system: Ubuntu

Architecture: wasm32-unknown-unknown, wasm32-wasip2 and maybe more

Extra Info

My testing output:

Converted 0 to: Ok(32.0)
Converted 32 to: Ok(89.6)
Converted 100 to: Ok(212.0)
Converted 100.1 to: Err(error while executing at wasm backtrace:
    0:   0x2e65 - guest.wasm!__rustc[90fd524071601a38]::__rust_abort
    1:   0x3980 - guest.wasm!__rustc[90fd524071601a38]::__rust_start_panic
    2:   0x393e - guest.wasm!__rustc[90fd524071601a38]::rust_panic
    3:   0x391f - guest.wasm!std::panicking::rust_panic_with_hook::h885a2e0f7cb6094c
    4:   0x2f31 - guest.wasm!std::panicking::begin_panic_handler::{{closure}}::hf631a5b49e1d8742
    5:   0x2e6b - guest.wasm!std::sys::backtrace::__rust_end_short_backtrace::h055708a75b60b26d
    6:   0x349a - guest.wasm!__rustc[90fd524071601a38]::rust_begin_unwind
    7:   0x3d6f - guest.wasm!core::panicking::panic_fmt::h3b9ae52b0e452a99
    8:    0x3e9 - guest.wasm!<guest::GuestComponent as guest::Guest>::convert_celsius_to_fahrenheit::hf763edc0af92d5f6
    9:    0x2f7 - guest.wasm!guest::_export_convert_celsius_to_fahrenheit_cabi::h7eba130e8e72a055
   10:    0x427 - guest.wasm!convert-celsius-to-fahrenheit
note: using the `WASMTIME_BACKTRACE_DETAILS=1` environment variable may show more debugging information

Caused by:
    wasm trap: wasm `unreachable` instruction executed

Stack backtrace:
   0: anyhow::error::<impl core::convert::From<E> for anyhow::Error>::from
             at /home/cxiao/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/anyhow-1.0.93/src/backtrace.rs:27:14
   1: <T as core::convert::Into<U>>::into
             at /home/cxiao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/convert/mod.rs:768:9
   2: wasmtime::runtime::trap::from_runtime_box
             at ./crates/wasmtime/src/runtime/trap.rs:101:39
   3: wasmtime::runtime::func::invoke_wasm_and_catch_traps::{{closure}}
             at ./crates/wasmtime/src/runtime/func.rs:1535:28
   4: core::result::Result<T,E>::map_err
             at /home/cxiao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/result.rs:914:27
   5: wasmtime::runtime::func::invoke_wasm_and_catch_traps
             at ./crates/wasmtime/src/runtime/func.rs:1535:16
   6: wasmtime::runtime::func::Func::call_unchecked_raw
             at ./crates/wasmtime/src/runtime/func.rs:1021:9
   7: wasmtime::runtime::component::func::Func::call_raw
             at ./crates/wasmtime/src/runtime/component/func.rs:456:13
   8: wasmtime::runtime::component::func::typed::TypedFunc<Params,Return>::call_impl
             at ./crates/wasmtime/src/runtime/component/func/typed.rs:234:27
   9: wasmtime::runtime::component::func::typed::TypedFunc<Params,Return>::call
             at ./crates/wasmtime/src/runtime/component/func/typed.rs:164:14
  10: component::_::<impl component::Convert>::call_convert_celsius_to_fahrenheit
             at ./examples/component/main.rs:10:1
  11: component::main
             at ./examples/component/main.rs:59:30
  12: core::ops::function::FnOnce::call_once
             at /home/cxiao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:250:5
  13: std::sys::backtrace::__rust_begin_short_backtrace
             at /home/cxiao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/backtrace.rs:152:18
  14: std::rt::lang_start::{{closure}}
             at /home/cxiao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:206:18
  15: core::ops::function::impls::<impl core::ops::function::FnOnce<A> for &F>::call_once
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/core/src/ops/function.rs:284:21
  16: std::panicking::catch_unwind::do_call
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/panicking.rs:589:40
  17: std::panicking::catch_unwind
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/panicking.rs:552:19
  18: std::panic::catch_unwind
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/panic.rs:359:14
  19: std::rt::lang_start_internal::{{closure}}
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/rt.rs:175:24
  20: std::panicking::catch_unwind::do_call
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/panicking.rs:589:40
  21: std::panicking::catch_unwind
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/panicking.rs:552:19
  22: std::panic::catch_unwind
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/panic.rs:359:14
  23: std::rt::lang_start_internal
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/rt.rs:171:5
  24: std::rt::lang_start
             at /home/cxiao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:205:5
  25: main
  26: <unknown>
  27: __libc_start_main
  28: _start)
Converted 31 to: Err(wasm trap: cannot enter component instance

Stack backtrace:
   0: anyhow::error::<impl core::convert::From<E> for anyhow::Error>::from
             at /home/cxiao/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/anyhow-1.0.93/src/backtrace.rs:27:14
   1: <T as core::convert::Into<U>>::into
             at /home/cxiao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/convert/mod.rs:768:9
   2: anyhow::kind::Trait::new
             at /home/cxiao/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/anyhow-1.0.93/src/kind.rs:95:15
   3: wasmtime::runtime::component::func::Func::call_raw
             at ./crates/wasmtime/src/runtime/component/func.rs:432:17
   4: wasmtime::runtime::component::func::typed::TypedFunc<Params,Return>::call_impl
             at ./crates/wasmtime/src/runtime/component/func/typed.rs:234:27
   5: wasmtime::runtime::component::func::typed::TypedFunc<Params,Return>::call
             at ./crates/wasmtime/src/runtime/component/func/typed.rs:164:14
   6: component::_::<impl component::Convert>::call_convert_celsius_to_fahrenheit
             at ./examples/component/main.rs:10:1
   7: component::main
             at ./examples/component/main.rs:59:30
   8: core::ops::function::FnOnce::call_once
             at /home/cxiao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:250:5
   9: std::sys::backtrace::__rust_begin_short_backtrace
             at /home/cxiao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/backtrace.rs:152:18
  10: std::rt::lang_start::{{closure}}
             at /home/cxiao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:206:18
  11: core::ops::function::impls::<impl core::ops::function::FnOnce<A> for &F>::call_once
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/core/src/ops/function.rs:284:21
  12: std::panicking::catch_unwind::do_call
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/panicking.rs:589:40
  13: std::panicking::catch_unwind
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/panicking.rs:552:19
  14: std::panic::catch_unwind
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/panic.rs:359:14
  15: std::rt::lang_start_internal::{{closure}}
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/rt.rs:175:24
  16: std::panicking::catch_unwind::do_call
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/panicking.rs:589:40
  17: std::panicking::catch_unwind
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/panicking.rs:552:19
  18: std::panic::catch_unwind
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/panic.rs:359:14
  19: std::rt::lang_start_internal
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/rt.rs:171:5
  20: std::rt::lang_start
             at /home/cxiao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:205:5
  21: main
  22: <unknown>
  23: __libc_start_main
  24: _start)
Converted 50 to: Err(wasm trap: cannot enter component instance

Stack backtrace:
   0: anyhow::error::<impl core::convert::From<E> for anyhow::Error>::from
             at /home/cxiao/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/anyhow-1.0.93/src/backtrace.rs:27:14
   1: <T as core::convert::Into<U>>::into
             at /home/cxiao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/convert/mod.rs:768:9
   2: anyhow::kind::Trait::new
             at /home/cxiao/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/anyhow-1.0.93/src/kind.rs:95:15
   3: wasmtime::runtime::component::func::Func::call_raw
             at ./crates/wasmtime/src/runtime/component/func.r
[message truncated]

Wasmtime GitHub notifications bot (Jun 20 2025 at 10:02):

xiaocq2001 added the bug label to Issue #11086.

Wasmtime GitHub notifications bot (Jun 20 2025 at 10:06):

bjorn3 commented on issue #11086:

This is intentional. Once a component traps, you are no longer allowed to enter it. LLVM considers continuing after a trap UB. While core wasm doesn't enfore that you don't re-enter the module after a trap, the wasm component model does enforce this.

Wasmtime GitHub notifications bot (Jun 20 2025 at 14:01):

alexcrichton closed issue #11086:

Steps to Reproduce

• first, modify examples/component/wasm/guest.rs to generate panic in some cases, let's say generate panic when input is over 100.0
• second, modify examples/component/main.rs to invoke the guest function several times and print the result directly, e.g., use these values: 0.0, 32.0, 100.0, 100.1, 31.0, 50.0.
• Check output to see function call fails

Expected Results

Just value >100 panics and since panic is catched by trap, I expect the subsequent component calls recover to normal state.

Actual Results

Component calls after the panic keep failing, returning "wasm trap: cannot enter component instance"

Versions and Environment

Wasmtime version or commit: cfe17cb1c61658a157e7ad9da2ecbe5f314a2536

Operating system: Ubuntu

Architecture: wasm32-unknown-unknown, wasm32-wasip2 and maybe more

Extra Info

My testing output:

Converted 0 to: Ok(32.0)
Converted 32 to: Ok(89.6)
Converted 100 to: Ok(212.0)
Converted 100.1 to: Err(error while executing at wasm backtrace:
    0:   0x2e65 - guest.wasm!__rustc[90fd524071601a38]::__rust_abort
    1:   0x3980 - guest.wasm!__rustc[90fd524071601a38]::__rust_start_panic
    2:   0x393e - guest.wasm!__rustc[90fd524071601a38]::rust_panic
    3:   0x391f - guest.wasm!std::panicking::rust_panic_with_hook::h885a2e0f7cb6094c
    4:   0x2f31 - guest.wasm!std::panicking::begin_panic_handler::{{closure}}::hf631a5b49e1d8742
    5:   0x2e6b - guest.wasm!std::sys::backtrace::__rust_end_short_backtrace::h055708a75b60b26d
    6:   0x349a - guest.wasm!__rustc[90fd524071601a38]::rust_begin_unwind
    7:   0x3d6f - guest.wasm!core::panicking::panic_fmt::h3b9ae52b0e452a99
    8:    0x3e9 - guest.wasm!<guest::GuestComponent as guest::Guest>::convert_celsius_to_fahrenheit::hf763edc0af92d5f6
    9:    0x2f7 - guest.wasm!guest::_export_convert_celsius_to_fahrenheit_cabi::h7eba130e8e72a055
   10:    0x427 - guest.wasm!convert-celsius-to-fahrenheit
note: using the `WASMTIME_BACKTRACE_DETAILS=1` environment variable may show more debugging information

Caused by:
    wasm trap: wasm `unreachable` instruction executed

Stack backtrace:
   0: anyhow::error::<impl core::convert::From<E> for anyhow::Error>::from
             at /home/cxiao/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/anyhow-1.0.93/src/backtrace.rs:27:14
   1: <T as core::convert::Into<U>>::into
             at /home/cxiao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/convert/mod.rs:768:9
   2: wasmtime::runtime::trap::from_runtime_box
             at ./crates/wasmtime/src/runtime/trap.rs:101:39
   3: wasmtime::runtime::func::invoke_wasm_and_catch_traps::{{closure}}
             at ./crates/wasmtime/src/runtime/func.rs:1535:28
   4: core::result::Result<T,E>::map_err
             at /home/cxiao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/result.rs:914:27
   5: wasmtime::runtime::func::invoke_wasm_and_catch_traps
             at ./crates/wasmtime/src/runtime/func.rs:1535:16
   6: wasmtime::runtime::func::Func::call_unchecked_raw
             at ./crates/wasmtime/src/runtime/func.rs:1021:9
   7: wasmtime::runtime::component::func::Func::call_raw
             at ./crates/wasmtime/src/runtime/component/func.rs:456:13
   8: wasmtime::runtime::component::func::typed::TypedFunc<Params,Return>::call_impl
             at ./crates/wasmtime/src/runtime/component/func/typed.rs:234:27
   9: wasmtime::runtime::component::func::typed::TypedFunc<Params,Return>::call
             at ./crates/wasmtime/src/runtime/component/func/typed.rs:164:14
  10: component::_::<impl component::Convert>::call_convert_celsius_to_fahrenheit
             at ./examples/component/main.rs:10:1
  11: component::main
             at ./examples/component/main.rs:59:30
  12: core::ops::function::FnOnce::call_once
             at /home/cxiao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:250:5
  13: std::sys::backtrace::__rust_begin_short_backtrace
             at /home/cxiao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/backtrace.rs:152:18
  14: std::rt::lang_start::{{closure}}
             at /home/cxiao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:206:18
  15: core::ops::function::impls::<impl core::ops::function::FnOnce<A> for &F>::call_once
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/core/src/ops/function.rs:284:21
  16: std::panicking::catch_unwind::do_call
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/panicking.rs:589:40
  17: std::panicking::catch_unwind
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/panicking.rs:552:19
  18: std::panic::catch_unwind
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/panic.rs:359:14
  19: std::rt::lang_start_internal::{{closure}}
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/rt.rs:175:24
  20: std::panicking::catch_unwind::do_call
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/panicking.rs:589:40
  21: std::panicking::catch_unwind
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/panicking.rs:552:19
  22: std::panic::catch_unwind
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/panic.rs:359:14
  23: std::rt::lang_start_internal
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/rt.rs:171:5
  24: std::rt::lang_start
             at /home/cxiao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:205:5
  25: main
  26: <unknown>
  27: __libc_start_main
  28: _start)
Converted 31 to: Err(wasm trap: cannot enter component instance

Stack backtrace:
   0: anyhow::error::<impl core::convert::From<E> for anyhow::Error>::from
             at /home/cxiao/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/anyhow-1.0.93/src/backtrace.rs:27:14
   1: <T as core::convert::Into<U>>::into
             at /home/cxiao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/convert/mod.rs:768:9
   2: anyhow::kind::Trait::new
             at /home/cxiao/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/anyhow-1.0.93/src/kind.rs:95:15
   3: wasmtime::runtime::component::func::Func::call_raw
             at ./crates/wasmtime/src/runtime/component/func.rs:432:17
   4: wasmtime::runtime::component::func::typed::TypedFunc<Params,Return>::call_impl
             at ./crates/wasmtime/src/runtime/component/func/typed.rs:234:27
   5: wasmtime::runtime::component::func::typed::TypedFunc<Params,Return>::call
             at ./crates/wasmtime/src/runtime/component/func/typed.rs:164:14
   6: component::_::<impl component::Convert>::call_convert_celsius_to_fahrenheit
             at ./examples/component/main.rs:10:1
   7: component::main
             at ./examples/component/main.rs:59:30
   8: core::ops::function::FnOnce::call_once
             at /home/cxiao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:250:5
   9: std::sys::backtrace::__rust_begin_short_backtrace
             at /home/cxiao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/backtrace.rs:152:18
  10: std::rt::lang_start::{{closure}}
             at /home/cxiao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:206:18
  11: core::ops::function::impls::<impl core::ops::function::FnOnce<A> for &F>::call_once
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/core/src/ops/function.rs:284:21
  12: std::panicking::catch_unwind::do_call
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/panicking.rs:589:40
  13: std::panicking::catch_unwind
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/panicking.rs:552:19
  14: std::panic::catch_unwind
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/panic.rs:359:14
  15: std::rt::lang_start_internal::{{closure}}
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/rt.rs:175:24
  16: std::panicking::catch_unwind::do_call
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/panicking.rs:589:40
  17: std::panicking::catch_unwind
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/panicking.rs:552:19
  18: std::panic::catch_unwind
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/panic.rs:359:14
  19: std::rt::lang_start_internal
             at /rustc/255aa220821c05c3eac7605fce4ea1c9ab2cbdb4/library/std/src/rt.rs:171:5
  20: std::rt::lang_start
             at /home/cxiao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:205:5
  21: main
  22: <unknown>
  23: __libc_start_main
  24: _start)
Converted 50 to: Err(wasm trap: cannot enter component instance

Stack backtrace:
   0: anyhow::error::<impl core::convert::From<E> for anyhow::Error>::from
             at /home/cxiao/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/anyhow-1.0.93/src/backtrace.rs:27:14
   1: <T as core::convert::Into<U>>::into
             at /home/cxiao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/convert/mod.rs:768:9
   2: anyhow::kind::Trait::new
             at /home/cxiao/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/anyhow-1.0.93/src/kind.rs:95:15
   3: wasmtime::runtime::component::func::Func::call_raw
             at ./crates/wasmtime/src/runtime/component/func
[message truncated]

Wasmtime GitHub notifications bot (Jun 20 2025 at 14:01):

alexcrichton commented on issue #11086:

Yes this is expected behavior, so I'm going to close this. @xiaocq2001 if you have a suggestion though about where best to document this let us know though!

Wasmtime GitHub notifications bot (Jun 23 2025 at 03:19):

xiaocq2001 commented on issue #11086:

Thanks for the quick response! So, if I want to make the component work again, I need to re-instantiate it, right? If I re-instantiate the component without re-creating the store, will there be any issues?

Wasmtime GitHub notifications bot (Jun 23 2025 at 14:32):

alexcrichton commented on issue #11086:

Yes that would work. While not problematic you may want to be aware that a store doesn't GC itself internally ever, meaning that any instances created within a store aren't deallocated until the store is deallocated. If that's a concern for you then you'll want to recreate the store each time, but if that's not a concern there's no issue putting more instances in a store.

Wasmtime GitHub notifications bot (Jun 24 2025 at 02:50):

xiaocq2001 commented on issue #11086:

Thanks for the clarification.

Regarding instances created within a store, I have a few questions based on the component example. Could you confirm if the following assumptions are correct?

• Local instances created inside convert_celsius_to_fahrenheit are deallocated if a panic occurs, e.g., a i32 variable.
• Global static instances created by convert_celsius_to_fahrenheit are not deallocated during a panic and will not be accessible if convert_celsius_to_fahrenheit is restarted. These instances remain allocated until the entire store is deallocated, e.g., a global static i32 variable.
  

Wasmtime GitHub notifications bot (Jun 24 2025 at 14:41):

alexcrichton commented on issue #11086:

Sort of I think, but panics in Rust do not run any destructors in the program at all. They're more like panic=abort semantics on native where the program aborts without doing anything else when a panic happens. You mention an i32 variable as a "local instance" but that's not really allocated anywhere. Panics do indeed clean up the stack but that's it, no destructors are run.

What I'm saying about instances staying in a store though is more a WebAssembly component instance than anything program-related. The WebAssembly component takes up resources such as tables, linear memories, etc, and all of those stay in the store. These then represent, inside them, program constructs like globals but it's moreso the host embedder resources I wanted to highlight.

Wasmtime GitHub notifications bot (Jun 26 2025 at 04:01):

xiaocq2001 commented on issue #11086:

Thanks very much.

Last updated: Dec 06 2025 at 06:05 UTC