Move trap handler initialization to per-Store (#1644)

Previously we initialized trap handling (signals/etc) once-per-instance
but that's a bit too granular since we only need to do this as
one-time per-program initialization. This moves the initialization to
`Store` instead which means that we'll call this at least once per
thread, which some platforms may need (none currently do, they all only
need per-program initialization, but Fuchsia will need per-thread
initialization).

crates/runtime/src/instance.rs

@@ -7,7 +7,6 @@ use crate::imports::Imports;
 use crate::jit_int::GdbJitImageRegistration;
 use crate::memory::{DefaultMemoryCreator, RuntimeLinearMemory, RuntimeMemoryCreator};
 use crate::table::Table;
-use crate::traphandlers;
 use crate::traphandlers::Trap;
 use crate::vmcontext::{
     VMBuiltinFunctionsArray, VMCallerCheckedAnyfunc, VMContext, VMFunctionBody, VMFunctionImport,
@@ -886,10 +885,6 @@ impl InstanceHandle {
         );
         *instance.interrupts() = &*instance.interrupts;
 
-        // Ensure that our signal handlers are ready for action.
-        // TODO: Move these calls out of `InstanceHandle`.
-        traphandlers::init();
-
         // Perform infallible initialization in this constructor, while fallible
         // initialization is deferred to the `initialize` method.
         initialize_passive_elements(instance);

crates/runtime/src/lib.rs

@@ -44,7 +44,7 @@ pub use crate::mmap::Mmap;
 pub use crate::sig_registry::SignatureRegistry;
 pub use crate::table::Table;
 pub use crate::traphandlers::{
-    catch_traps, raise_lib_trap, raise_user_trap, resume_panic, SignalHandler, Trap,
+    catch_traps, init_traps, raise_lib_trap, raise_user_trap, resume_panic, SignalHandler, Trap,
 };
 pub use crate::vmcontext::{
     VMCallerCheckedAnyfunc, VMContext, VMFunctionBody, VMFunctionImport, VMGlobalDefinition,

crates/runtime/src/traphandlers.rs

@@ -253,7 +253,7 @@ cfg_if::cfg_if! {
 /// function needs to be called at the end of the startup process, after other
 /// handlers have been installed. This function can thus be called multiple
 /// times, having no effect after the first call.
-pub fn init() {
+pub fn init_traps() {
     static INIT: Once = Once::new();
     INIT.call_once(real_init);
 }