Naive short circuiting implementation for user panics and results. (#167)

* Add panic and result catching

* exit process on panic and user runtime error

* Complete initial implementation

lib/clif-backend/src/module.rs

@@ -16,7 +16,7 @@ use wasmer_runtime_core::{
     cache::{Cache, Error as CacheError},
 };
 use wasmer_runtime_core::{
-    backend::{Backend, FuncResolver, ProtectedCaller, Token},
+    backend::{Backend, FuncResolver, ProtectedCaller, Token, UserTrapper},
     error::{CompileResult, RuntimeResult},
     module::{ModuleInfo, ModuleInner, StringTable},
     structures::{Map, TypedIndex},
@@ -51,6 +51,10 @@ impl ProtectedCaller for Placeholder {
     ) -> RuntimeResult<Vec<Value>> {
         Ok(vec![])
     }
+
+    fn get_early_trapper(&self) -> Box<dyn UserTrapper> {
+        unimplemented!()
+    }
 }
 
 /// This contains all of the items in a `ModuleInner` except the `func_resolver`.

lib/clif-backend/src/signal/mod.rs

@@ -2,9 +2,9 @@ use crate::relocation::{TrapData, TrapSink};
 use crate::trampoline::Trampolines;
 use hashbrown::HashSet;
 use libc::c_void;
-use std::sync::Arc;
+use std::{cell::Cell, sync::Arc};
 use wasmer_runtime_core::{
-    backend::{ProtectedCaller, Token},
+    backend::{ProtectedCaller, Token, UserTrapper},
     error::RuntimeResult,
     export::Context,
     module::{ExportIndex, ModuleInfo, ModuleInner},
@@ -24,6 +24,19 @@ pub use self::unix::*;
 #[cfg(windows)]
 pub use self::windows::*;
 
+thread_local! {
+    pub static TRAP_EARLY_DATA: Cell<Option<String>> = Cell::new(None);
+}
+
+pub struct Trapper;
+
+impl UserTrapper for Trapper {
+    unsafe fn do_early_trap(&self, msg: String) -> ! {
+        TRAP_EARLY_DATA.with(|cell| cell.set(Some(msg)));
+        trigger_trap()
+    }
+}
+
 pub struct Caller {
     func_export_set: HashSet<FuncIndex>,
     handler_data: HandlerData,
@@ -118,6 +131,10 @@ impl ProtectedCaller for Caller {
             })
             .collect())
     }
+
+    fn get_early_trapper(&self) -> Box<dyn UserTrapper> {
+        Box::new(Trapper)
+    }
 }
 
 fn get_func_from_index(

lib/clif-backend/src/signal/unix.rs

@@ -9,7 +9,7 @@
 //! are very special, the async signal unsafety of Rust's TLS implementation generally does not affect the correctness here
 //! unless you have memory unsafety elsewhere in your code.
 //!
-use crate::relocation::{TrapCode, TrapData, TrapSink};
+use crate::relocation::{TrapCode, TrapData};
 use crate::signal::HandlerData;
 use libc::{c_int, c_void, siginfo_t};
 use nix::sys::signal::{
@@ -60,6 +60,12 @@ thread_local! {
     pub static CURRENT_EXECUTABLE_BUFFER: Cell<*const c_void> = Cell::new(ptr::null());
 }
 
+pub unsafe fn trigger_trap() -> ! {
+    let jmp_buf = SETJMP_BUFFER.with(|buf| buf.get());
+
+    longjmp(jmp_buf as *mut c_void, 0)
+}
+
 pub fn call_protected<T>(handler_data: &HandlerData, f: impl FnOnce() -> T) -> RuntimeResult<T> {
     unsafe {
         let jmp_buf = SETJMP_BUFFER.with(|buf| buf.get());
@@ -72,6 +78,10 @@ pub fn call_protected<T>(handler_data: &HandlerData, f: impl FnOnce() -> T) -> R
         let signum = setjmp(jmp_buf as *mut _);
         if signum != 0 {
             *jmp_buf = prev_jmp_buf;
+
+            if let Some(msg) = super::TRAP_EARLY_DATA.with(|cell| cell.replace(None)) {
+                Err(RuntimeError::User { msg })
+            } else {
                 let (faulting_addr, inst_ptr) = CAUGHT_ADDRESSES.with(|cell| cell.get());
 
                 if let Some(TrapData {
@@ -121,6 +131,7 @@ pub fn call_protected<T>(handler_data: &HandlerData, f: impl FnOnce() -> T) -> R
                     }
                     .into())
                 }
+            }
         } else {
             let ret = f(); // TODO: Switch stack?
             *jmp_buf = prev_jmp_buf;

lib/runtime-core/src/backend.rs

@@ -82,6 +82,12 @@ pub trait ProtectedCaller: Send + Sync {
         vmctx: *mut vm::Ctx,
         _: Token,
     ) -> RuntimeResult<Vec<Value>>;
+
+    fn get_early_trapper(&self) -> Box<dyn UserTrapper>;
+}
+
+pub trait UserTrapper {
+    unsafe fn do_early_trap(&self, msg: String) -> !;
 }
 
 pub trait FuncResolver: Send + Sync {

lib/runtime-core/src/error.rs

@@ -97,6 +97,9 @@ pub enum RuntimeError {
         table: TableIndex,
     },
     IllegalArithmeticOperation,
+    User {
+        msg: String,
+    },
     Unknown {
         msg: String,
     },

lib/runtime-core/src/instance.rs

@@ -7,7 +7,6 @@ use crate::{
     import::{ImportObject, LikeNamespace},
     memory::Memory,
     module::{ExportIndex, Module, ModuleInner},
-    sig_registry::SigRegistry,
     table::Table,
     typed_func::{Func, Safe, WasmTypeList},
     types::{FuncIndex, FuncSig, GlobalIndex, LocalOrImport, MemoryIndex, TableIndex, Value},

lib/runtime-core/src/module.rs

@@ -3,6 +3,7 @@ use crate::{
     error::Result,
     import::ImportObject,
     structures::{Map, TypedIndex},
+    typed_func::EARLY_TRAPPER,
     types::{
         FuncIndex, FuncSig, GlobalDescriptor, GlobalIndex, GlobalInit, ImportedFuncIndex,
         ImportedGlobalIndex, ImportedMemoryIndex, ImportedTableIndex, Initializer,
@@ -63,6 +64,10 @@ pub struct Module(#[doc(hidden)] pub Arc<ModuleInner>);
 
 impl Module {
     pub(crate) fn new(inner: Arc<ModuleInner>) -> Self {
+        unsafe {
+            EARLY_TRAPPER
+                .with(|ucell| *ucell.get() = Some(inner.protected_caller.get_early_trapper()));
+        }
         Module(inner)
     }
 

lib/runtime-core/src/typed_func.rs

@@ -1,11 +1,16 @@
 use crate::{
+    backend::UserTrapper,
     error::RuntimeError,
     export::{Context, Export, FuncPointer},
     import::IsExport,
     types::{FuncSig, Type, WasmExternType},
     vm::Ctx,
 };
-use std::{marker::PhantomData, mem, ptr, sync::Arc};
+use std::{cell::UnsafeCell, fmt, marker::PhantomData, mem, panic, ptr, sync::Arc};
+
+thread_local! {
+    pub static EARLY_TRAPPER: UnsafeCell<Option<Box<dyn UserTrapper>>> = UnsafeCell::new(None);
+}
 
 pub trait Safeness {}
 pub struct Safe;
@@ -28,9 +33,44 @@ where
     Args: WasmTypeList,
     Rets: WasmTypeList,
 {
-    fn to_raw(self) -> *const ();
+    fn to_raw(&self) -> *const ();
 }
 
+pub trait TrapEarly<Rets>
+where
+    Rets: WasmTypeList,
+{
+    fn report(self) -> Result<Rets, String>;
+}
+
+impl<Rets> TrapEarly<Rets> for Rets
+where
+    Rets: WasmTypeList,
+{
+    fn report(self) -> Result<Rets, String> {
+        Ok(self)
+    }
+}
+
+impl<Rets, E> TrapEarly<Rets> for Result<Rets, E>
+where
+    Rets: WasmTypeList,
+    E: fmt::Debug,
+{
+    fn report(self) -> Result<Rets, String> {
+        self.map_err(|err| format!("Error: {:?}", err))
+    }
+}
+
+// pub fn Func<'a, Args, Rets, F>(f: F) -> Func<'a, Args, Rets, Unsafe>
+// where
+//     Args: WasmTypeList,
+//     Rets: WasmTypeList,
+//     F: ExternalFunction<Args, Rets>
+// {
+//     Func::new(f)
+// }
+
 pub struct Func<'a, Args = (), Rets = (), Safety: Safeness = Safe> {
     f: *const (),
     ctx: *mut Ctx,
@@ -143,18 +183,41 @@ macro_rules! impl_traits {
             }
         }
 
-        impl< $( $x: WasmExternType, )* Rets: WasmTypeList, FN: Fn( $( $x, )* &mut Ctx) -> Rets> ExternalFunction<($( $x ),*), Rets> for FN {
+        impl< $( $x: WasmExternType, )* Rets: WasmTypeList, Trap: TrapEarly<Rets>, FN: Fn( $( $x, )* &mut Ctx) -> Trap> ExternalFunction<($( $x ),*), Rets> for FN {
             #[allow(non_snake_case)]
-            fn to_raw(self) -> *const () {
+            fn to_raw(&self) -> *const () {
                 assert_eq!(mem::size_of::<Self>(), 0, "you cannot use a closure that captures state for `Func`.");
 
-                extern fn wrap<$( $x: WasmExternType, )* Rets: WasmTypeList, FN: Fn( $( $x, )* &mut Ctx) -> Rets>( $( $x: $x, )* ctx: &mut Ctx) -> Rets::CStruct {
+                extern fn wrap<$( $x: WasmExternType, )* Rets: WasmTypeList, Trap: TrapEarly<Rets>, FN: Fn( $( $x, )* &mut Ctx) -> Trap>( $( $x: $x, )* ctx: &mut Ctx) -> Rets::CStruct {
                     let f: FN = unsafe { mem::transmute_copy(&()) };
-                    let rets = f( $( $x, )* ctx);
-                    rets.into_c_struct()
+
+                    let msg = match panic::catch_unwind(panic::AssertUnwindSafe(|| {
+                        f( $( $x, )* ctx).report()
+                    })) {
+                        Ok(Ok(returns)) => return returns.into_c_struct(),
+                        Ok(Err(err)) => err,
+                        Err(err) => {
+                            if let Some(s) = err.downcast_ref::<&str>() {
+                                s.to_string()
+                            } else if let Some(s) = err.downcast_ref::<String>() {
+                                s.clone()
+                            } else {
+                                "a panic occurred, but no additional information is available".to_string()
+                            }
+                        },
+                    };
+
+                    unsafe {
+                        if let Some(early_trapper) = &*EARLY_TRAPPER.with(|ucell| ucell.get()) {
+                            early_trapper.do_early_trap(msg)
+                        } else {
+                            eprintln!("panic handling not setup");
+                            std::process::exit(1)
+                        }
+                    }
                 }
 
-                wrap::<$( $x, )* Rets, Self> as *const ()
+                wrap::<$( $x, )* Rets, Trap, Self> as *const ()
             }
         }
 

lib/runtime-core/src/vm.rs

@@ -493,7 +493,7 @@ mod vm_ctx_tests {
 
     fn generate_module() -> ModuleInner {
         use super::Func;
-        use crate::backend::{Backend, FuncResolver, ProtectedCaller, Token};
+        use crate::backend::{Backend, FuncResolver, ProtectedCaller, Token, UserTrapper};
         use crate::error::RuntimeResult;
         use crate::types::{FuncIndex, LocalFuncIndex, Value};
         use hashbrown::HashMap;
@@ -520,6 +520,9 @@ mod vm_ctx_tests {
             ) -> RuntimeResult<Vec<Value>> {
                 Ok(vec![])
             }
+            fn get_early_trapper(&self) -> Box<dyn UserTrapper> {
+                unimplemented!()
+            }
         }
 
         ModuleInner {

lib/spectests/examples/simple/main.rs

@@ -3,7 +3,7 @@ use wabt::wat2wasm;
 use wasmer_clif_backend::CraneliftCompiler;
 use wasmer_runtime_core::{
     cache::Cache,
-    error::Result,
+    error,
     global::Global,
     memory::Memory,
     prelude::*,
@@ -14,7 +14,7 @@ use wasmer_runtime_core::{
 
 static EXAMPLE_WASM: &'static [u8] = include_bytes!("simple.wasm");
 
-fn main() -> Result<()> {
+fn main() -> error::Result<()> {
     let compiler = CraneliftCompiler::new();
     let wasm_binary = wat2wasm(IMPORT_MODULE.as_bytes()).expect("WAST not valid or malformed");
 
@@ -61,14 +61,14 @@ fn main() -> Result<()> {
     Ok(())
 }
 
-fn print_num(n: i32, ctx: &mut vm::Ctx) -> i32 {
+fn print_num(n: i32, ctx: &mut vm::Ctx) -> Result<i32, ()> {
     println!("print_num({})", n);
 
     let memory: &Memory = ctx.memory(0);
 
     let a: i32 = memory.view()[0].get();
 
-    a + n + 1
+    Ok(a + n + 1)
 }
 
 static IMPORT_MODULE: &str = r#"