Wasmtime GitHub notifications bot (Dec 28 2024 at 15:46): Wasmtime GitHub notifications bot (Dec 28 2024 at 15:46):puremourning added the bug label to Issue #9909.
Wasmtime GitHub notifications bot (Dec 28 2024 at 15:46):puremourning opened issue #9909:
According to the documentation it should be possible to use a source/line debugger with guest code running inside the wasmtime VM.
This works well for rust embeddings, but when using the
c-api(or anything based on it, likewasmtime-cpp), the DWARF data is not exposed to the debugger.After a little investigation and debugging, this is because the
debug-builtinscargo feature is not enabled in builds of the C api crate.Test Case
https://docs.wasmtime.dev/examples-c-debugging.html
Steps to Reproduce
- build the C api:
cmake -S crates/c-api -B target/c-api --install-prefix "$(pwd)/artifacts" \ -DCMAKE_BUILD_TYPE=Debug \ -DCMAKE_EXPORT_COMPILE_COMMANDS=ON cmake --build target/c-api --parallel 16 cmake --install target/c-api
- Build the example fib wasm
rustup target add wasm32-unknown-unknown cargo build -p example-fib-debug-wasm --target wasm32-unknown-unknown
- Build the example
main.cabove:cd examples/fib-debug gcc main.c -I../../artifacts/include -L../../artifacts/lib -Xlinker -rpath $(pwd)/../../artifacts/lib -Xlinker -lwasmtime
- Run the example in debugger (e.g. lldb)
ben@BenMBP2021 wasmtime % lldb examples/fib-debug/a.out (lldb) target create "examples/fib-debug/a.out" Current executable set to '/Users/ben/Development/wasm/wasmtime/examples/fib-debug/a.out' (arm64). (lldb) settings set plugin.jit-loader.gdb.enable on (lldb) break set -f examples/fib-debug/wasm/fib.rs -l 3 Breakpoint 1: no locations (pending). WARNING: Unable to resolve breakpoint to any actual locations. (lldb) run Process 55426 launched: '/Users/ben/Development/wasm/wasmtime/examples/fib-debug/a.out' (arm64) Initializing... Loading binary... Compiling module... Instantiating module... Calling fib... > fib(6) = 21 Shutting down... Done. Process 55426 exited with status = 0 (0x00000000)Expected Results
- Breakpoint is hit in the fib.rs file
Actual Results
- No breakpoint is hit
Versions and Environment
Wasmtime version or commit: 01a43ed65d00d92807c7a8ae075ba9a948814c83
Operating system: macOS
Architecture: arm64
Extra Info
I made a quick patch to enable the feature, repeated the test above and it works.
ben@BenMBP2021 wasmtime % lldb examples/fib-debug/a.out (lldb) target create "examples/fib-debug/a.out" Current executable set to '/Users/ben/Development/wasm/wasmtime/examples/fib-debug/a.out' (arm64). (lldb) break set -f /Users/ben/Devel^Cment/wasm/wasmtime/examples/fib-debug/wasm/fib.rs -l 3 bck?options b (lldb) settings set plugin.jit-loader.gdb.enable on (lldb) break set -f examples/fib-debug/wasm/fib.rs -l 3 Breakpoint 1: no locations (pending). WARNING: Unable to resolve breakpoint to any actual locations. (lldb) run Process 55596 launched: '/Users/ben/Development/wasm/wasmtime/examples/fib-debug/a.out' (arm64) Initializing... Loading binary... Compiling module... 1 location added to breakpoint 1 Instantiating module... Calling fib... Process 55596 stopped * thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1 frame #0: 0x0000000100090040 JIT(0x1402a8000)`fib(n=6) at fib.rs:3:17 1 #[no_mangle] 2 pub extern "C" fn fib(n: u32) -> u32 { -> 3 let mut a = 1; 4 let mut b = 1; 5 for _ in 0..n { 6 let t = a; 7 a = b; JIT(0x1402a8000)`fib: -> 0x100090040 <+64>: mov w0, #0x1 ; =1 0x100090044 <+68>: ldr x1, [x2, #0x60] 0x100090048 <+72>: add x1, x1, #0x10 0x10009004c <+76>: str w0, [x1, w22, uxtw] Target 0: (a.out) stopped. warning: This version of LLDB has no plugin for the language "rust". Inspection of frame variables will be limited. (lldb)Here's the trivial patch:
commit 8f69c41d998ddb33b1d099b913f104cb93ba1b3d (HEAD -> main) Author: Ben Jackson <puremourning@gmail.com> Date: Sat Dec 28 15:31:54 2024 +0000 Enable JIT DWARF info in c-api diff --git a/crates/c-api/Cargo.toml b/crates/c-api/Cargo.toml index 84b7d45ed..d77312f42 100644 --- a/crates/c-api/Cargo.toml +++ b/crates/c-api/Cargo.toml @@ -56,5 +56,6 @@ gc-drc = ["wasmtime/gc-drc"] gc-null = ["wasmtime/gc-null"] cranelift = ['wasmtime/cranelift'] winch = ['wasmtime/winch'] +debug-builtins = ['wasmtime/debug-builtins'] # ... if you add a line above this be sure to change the other locations # marked WASMTIME_FEATURE_LIST diff --git a/crates/c-api/artifact/Cargo.toml b/crates/c-api/artifact/Cargo.toml index 1eb6659ec..8aa846d23 100644 --- a/crates/c-api/artifact/Cargo.toml +++ b/crates/c-api/artifact/Cargo.toml @@ -38,6 +38,7 @@ default = [ 'gc-null', 'cranelift', 'winch', + 'debug-builtins', # ... if you add a line above this be sure to change the other locations # marked WASMTIME_FEATURE_LIST ] @@ -58,5 +59,6 @@ gc-drc = ["wasmtime-c-api/gc-drc"] gc-null = ["wasmtime-c-api/gc-null"] cranelift = ["wasmtime-c-api/cranelift"] winch = ["wasmtime-c-api/winch"] +debug-builtins = ["wasmtime-c-api/debug-builtins"] # ... if you add a line above this be sure to read the comment at the end of # `default` diff --git a/crates/c-api/build.rs b/crates/c-api/build.rs index b500fd1bf..12bc0b501 100644 --- a/crates/c-api/build.rs +++ b/crates/c-api/build.rs @@ -19,6 +19,7 @@ const FEATURES: &[&str] = &[ "GC_NULL", "CRANELIFT", "WINCH", + "DEBUG_BUILTINS", ]; // ... if you add a line above this be sure to change the other locations // marked WASMTIME_FEATURE_LIST diff --git a/crates/c-api/cmake/features.cmake b/crates/c-api/cmake/features.cmake index 385c13965..727412a04 100644 --- a/crates/c-api/cmake/features.cmake +++ b/crates/c-api/cmake/features.cmake @@ -43,5 +43,6 @@ feature(gc-null ON) feature(async ON) feature(cranelift ON) feature(winch ON) +feature(debug-builtins ON) # ... if you add a line above this be sure to change the other locations # marked WASMTIME_FEATURE_LIST diff --git a/crates/c-api/include/wasmtime/conf.h.in b/crates/c-api/include/wasmtime/conf.h.in index 3dff987ac..03f4debf9 100644 --- a/crates/c-api/include/wasmtime/conf.h.in +++ b/crates/c-api/include/wasmtime/conf.h.in @@ -25,6 +25,7 @@ #cmakedefine WASMTIME_FEATURE_ASYNC #cmakedefine WASMTIME_FEATURE_CRANELIFT #cmakedefine WASMTIME_FEATURE_WINCH +#cmakedefine WASMTIME_FEATURE_DEBUG_BUILTINS // ... if you add a line above this be sure to change the other locations // marked WASMTIME_FEATURE_LISTI'm not clear if the issue here is the feature _should_ be enabled, and the docs are right, or a decision was made to not enable it, and the docs are wrong, or if there is some other way to enable this feature in the C-api or other C embeddings.
Last updated: Jan 24 2025 at 00:11 UTC