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wasm: fix roc_panic message retrieval

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Brian Carroll 2022-02-28 21:51:45 +00:00
parent 21a3ed4258
commit 85ba3154ec
1 changed files with 28 additions and 14 deletions
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42
compiler/test_gen/src/helpers/wasm.rs
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@ -1,8 +1,6 @@
use core::cell::Cell;
use libc::c_char;
use roc_gen_wasm::wasm_module::{Export, ExportType};
use std::collections::hash_map::DefaultHasher;
use std::ffi::CStr;
use std::hash::{Hash, Hasher};
use std::marker::PhantomData;
use std::path::{Path, PathBuf};
@ -196,19 +194,10 @@ where
match test_wrapper.call(&[]) {
Err(e) => {
// Check if the error is from roc_panic
// Our test roc_panic stores a pointer to its message in a global variable so we can find it.
let panic_msg_global = instance.exports.get_global(PANIC_MSG_NAME).unwrap();
let panic_msg_index = panic_msg_global.get().unwrap_i32() as usize;
if panic_msg_index == 0 {
// Pointer is null. The error isn't a roc_panic.
Err(e.to_string())
if let Some(msg) = get_roc_panic_msg(&instance, memory) {
Err(msg)
} else {
let memory_bytes = unsafe { memory.data_unchecked() };
let msg_ptr = memory_bytes[panic_msg_index..].as_ptr() as *const c_char;
let msg_cstr = unsafe { CStr::from_ptr(msg_ptr) };
let msg_str = msg_cstr.to_str().unwrap();
Err(msg_str.into())
Err(e.to_string())
}
}
Ok(result) => {
@ -231,6 +220,31 @@ where
}
}
/// Our test roc_panic stores a pointer to its message in a global variable so we can find it.
fn get_roc_panic_msg(instance: &wasmer::Instance, memory: &Memory) -> Option<String> {
let memory_bytes = unsafe { memory.data_unchecked() };
// We need to dereference twice!
// The Wasm Global only points at the memory location of the C global value
let panic_msg_global = instance.exports.get_global(PANIC_MSG_NAME).unwrap();
let global_addr = panic_msg_global.get().unwrap_i32() as usize;
let global_ptr = memory_bytes[global_addr..].as_ptr() as *const u32;
// Dereference again to find the bytes of the message string
let msg_addr = unsafe { *global_ptr };
if msg_addr == 0 {
return None;
}
let msg_index = msg_addr as usize;
let msg_len = memory_bytes[msg_index..]
.iter()
.position(|c| *c == 0)
.unwrap();
let msg_bytes = memory_bytes[msg_index..][..msg_len].to_vec();
let msg = unsafe { String::from_utf8_unchecked(msg_bytes) };
Some(msg)
}
#[allow(dead_code)]
pub fn assert_wasm_refcounts_help<T>(
src: &str,