Enables conditional compilation with gc

- Remove gc from default on c-api
- Adds fallback implementation for when gc is not enabled

Author: tolumide-ng

.github/workflows/main.yml

@@ -409,6 +409,7 @@ jobs:
               -p wasmtime-c-api --no-default-features
               -p wasmtime-c-api --no-default-features --features wat
               -p wasmtime-c-api --no-default-features --features wasi
+              -p wasmtime-c-api --no-default-features --features gc
 
           - name: wasmtime-wasi-http
             checks: |

crates/c-api/Cargo.toml

@@ -42,7 +42,6 @@ futures = { workspace = true, optional = true }
 
 [features]
 # WASMTIME_FEATURE_LIST
-default = ["gc"]
 async = ['wasmtime/async', 'futures']
 profiling = ["wasmtime/profiling"]
 cache = ["wasmtime/cache"]

crates/c-api/src/config.rs

@@ -91,20 +91,32 @@ pub extern "C" fn wasmtime_config_wasm_tail_call_set(c: &mut wasm_config_t, enab
 
 #[unsafe(no_mangle)]
 pub extern "C" fn wasmtime_config_wasm_reference_types_set(c: &mut wasm_config_t, enable: bool) {
+    #[cfg(feature = "gc")]
     c.config.wasm_reference_types(enable);
+
+    #[cfg(not(feature = "gc"))]
+    let _ = (c, enable);
 }
 
 #[unsafe(no_mangle)]
 pub extern "C" fn wasmtime_config_wasm_function_references_set(
     c: &mut wasm_config_t,
     enable: bool,
 ) {
+    #[cfg(feature = "gc")]
     c.config.wasm_function_references(enable);
+
+    #[cfg(not(feature = "gc"))]
+    let _ = (c, enable);
 }
 
 #[unsafe(no_mangle)]
 pub extern "C" fn wasmtime_config_wasm_gc_set(c: &mut wasm_config_t, enable: bool) {
+    #[cfg(feature = "gc")]
     c.config.wasm_gc(enable);
+
+    #[cfg(not(feature = "gc"))]
+    let _ = (c, enable);
 }
 
 #[unsafe(no_mangle)]
@@ -477,7 +489,11 @@ pub extern "C" fn wasmtime_config_wasm_wide_arithmetic_set(c: &mut wasm_config_t
 
 #[unsafe(no_mangle)]
 pub extern "C" fn wasmtime_config_wasm_exceptions_set(c: &mut wasm_config_t, enable: bool) {
+    #[cfg(feature = "gc")]
     c.config.wasm_exceptions(enable);
+
+    #[cfg(not(feature = "gc"))]
+    let _ = (c, enable);
 }
 
 #[unsafe(no_mangle)]

crates/c-api/src/func.rs

@@ -10,9 +10,11 @@ use std::mem::{self, MaybeUninit};
 use std::panic::{self, AssertUnwindSafe};
 use std::ptr;
 use std::str;
+#[cfg(feature = "gc")]
+use wasmtime::RootScope;
 use wasmtime::{
-    AsContext, AsContextMut, Error, Extern, Func, Result, RootScope, StoreContext, StoreContextMut,
-    Trap, Val, ValRaw,
+    AsContext, AsContextMut, Error, Extern, Func, Result, StoreContext, StoreContextMut, Trap, Val,
+    ValRaw,
 };
 
 #[derive(Clone)]
@@ -351,38 +353,74 @@ pub unsafe extern "C" fn wasmtime_func_call(
     nresults: usize,
     trap_ret: &mut *mut wasm_trap_t,
 ) -> Option<Box<wasmtime_error_t>> {
-    let mut scope = RootScope::new(&mut store);
-    let mut params = mem::take(&mut scope.as_context_mut().data_mut().wasm_val_storage);
-    let (wt_params, wt_results) = translate_args(
-        &mut params,
-        crate::slice_from_raw_parts(args, nargs)
-            .iter()
-            .map(|i| i.to_val(&mut scope)),
-        nresults,
-    );
+    #[cfg(feature = "gc")]
+    {
+        let mut scope = RootScope::new(&mut store);
+        let mut params = mem::take(&mut scope.as_context_mut().data_mut().wasm_val_storage);
+        let (wt_params, wt_results) = translate_args(
+            &mut params,
+            crate::slice_from_raw_parts(args, nargs)
+                .iter()
+                .map(|i| i.to_val(&mut scope)),
+            nresults,
+        );
 
-    // We're calling arbitrary code here most of the time, and we in general
-    // want to try to insulate callers against bugs in wasmtime/wasi/etc if we
-    // can. As a result we catch panics here and transform them to traps to
-    // allow the caller to have any insulation possible against Rust panics.
-    let result = panic::catch_unwind(AssertUnwindSafe(|| {
-        func.call(&mut scope, wt_params, wt_results)
-    }));
-    match result {
-        Ok(Ok(())) => {
-            let results = crate::slice_from_raw_parts_mut(results, nresults);
-            for (slot, val) in results.iter_mut().zip(wt_results.iter()) {
-                crate::initialize(slot, wasmtime_val_t::from_val(&mut scope, *val));
+        // We're calling arbitrary code here most of the time, and we in general
+        // want to try to insulate callers against bugs in wasmtime/wasi/etc if we
+        // can. As a result we catch panics here and transform them to traps to
+        // allow the caller to have any insulation possible against Rust panics.
+        let result = panic::catch_unwind(AssertUnwindSafe(|| {
+            func.call(&mut scope, wt_params, wt_results)
+        }));
+        match result {
+            Ok(Ok(())) => {
+                let results = crate::slice_from_raw_parts_mut(results, nresults);
+                for (slot, val) in results.iter_mut().zip(wt_results.iter()) {
+                    crate::initialize(slot, wasmtime_val_t::from_val(&mut scope, *val));
+                }
+                params.truncate(0);
+                scope.as_context_mut().data_mut().wasm_val_storage = params;
+                None
+            }
+            Ok(Err(trap)) => store_err(trap, trap_ret),
+            Err(panic) => {
+                let err = error_from_panic(panic);
+                *trap_ret = Box::into_raw(Box::new(wasm_trap_t::new(err)));
+                None
             }
-            params.truncate(0);
-            scope.as_context_mut().data_mut().wasm_val_storage = params;
-            None
         }
-        Ok(Err(trap)) => store_err(trap, trap_ret),
-        Err(panic) => {
-            let err = error_from_panic(panic);
-            *trap_ret = Box::into_raw(Box::new(wasm_trap_t::new(err)));
-            None
+    }
+
+    #[cfg(not(feature = "gc"))]
+    {
+        let mut params = mem::take(&mut store.data_mut().wasm_val_storage);
+        let (wt_params, wt_results) = translate_args(
+            &mut params,
+            crate::slice_from_raw_parts(args, nargs)
+                .iter()
+                .map(|i| i.to_val_unscoped(&mut store)),
+            nresults,
+        );
+
+        let result = panic::catch_unwind(AssertUnwindSafe(|| {
+            func.call(&mut store, wt_params, wt_results)
+        }));
+        match result {
+            Ok(Ok(())) => {
+                let results = crate::slice_from_raw_parts_mut(results, nresults);
+                for (slot, val) in results.iter_mut().zip(wt_results.iter()) {
+                    crate::initialize(slot, wasmtime_val_t::from_val_unscoped(&mut store, *val));
+                }
+                params.truncate(0);
+                store.data_mut().wasm_val_storage = params;
+                None
+            }
+            Ok(Err(trap)) => store_err(trap, trap_ret),
+            Err(panic) => {
+                let err = error_from_panic(panic);
+                *trap_ret = Box::into_raw(Box::new(wasm_trap_t::new(err)));
+                None
+            }
         }
     }
 }

crates/c-api/src/global.rs

@@ -3,7 +3,9 @@ use crate::{
     wasm_store_t, wasm_val_t, wasmtime_error_t, wasmtime_val_t,
 };
 use std::mem::MaybeUninit;
-use wasmtime::{Extern, Global, RootScope};
+#[cfg(feature = "gc")]
+use wasmtime::RootScope;
+use wasmtime::{Extern, Global};
 
 #[derive(Clone)]
 #[repr(transparent)]
@@ -84,12 +86,24 @@ pub unsafe extern "C" fn wasmtime_global_new(
     val: &wasmtime_val_t,
     ret: &mut Global,
 ) -> Option<Box<wasmtime_error_t>> {
-    let mut scope = RootScope::new(&mut store);
-    let val = val.to_val(&mut scope);
-    let global = Global::new(scope, gt.ty().ty.clone(), val);
-    handle_result(global, |global| {
-        *ret = global;
-    })
+    #[cfg(feature = "gc")]
+    {
+        let mut scope = RootScope::new(&mut store);
+        let val = val.to_val(&mut scope);
+        let global = Global::new(scope, gt.ty().ty.clone(), val);
+        handle_result(global, |global| {
+            *ret = global;
+        })
+    }
+
+    #[cfg(not(feature = "gc"))]
+    {
+        let val = val.to_val_unscoped(&mut store);
+        let global = Global::new(&mut store, gt.ty().ty.clone(), val);
+        handle_result(global, |global| {
+            *ret = global;
+        })
+    }
 }
 
 #[unsafe(no_mangle)]
@@ -106,9 +120,20 @@ pub extern "C" fn wasmtime_global_get(
     global: &Global,
     val: &mut MaybeUninit<wasmtime_val_t>,
 ) {
-    let mut scope = RootScope::new(store);
-    let gval = global.get(&mut scope);
-    crate::initialize(val, wasmtime_val_t::from_val(&mut scope, gval))
+    let mut store = store;
+
+    #[cfg(feature = "gc")]
+    {
+        let mut scope = RootScope::new(&mut store);
+        let gval = global.get(&mut scope);
+        crate::initialize(val, wasmtime_val_t::from_val(&mut scope, gval))
+    }
+
+    #[cfg(not(feature = "gc"))]
+    {
+        let gval = global.get(&mut store);
+        crate::initialize(val, wasmtime_val_t::from_val_unscoped(&mut store, gval))
+    }
 }
 
 #[unsafe(no_mangle)]
@@ -117,7 +142,16 @@ pub unsafe extern "C" fn wasmtime_global_set(
     global: &Global,
     val: &wasmtime_val_t,
 ) -> Option<Box<wasmtime_error_t>> {
-    let mut scope = RootScope::new(&mut store);
-    let val = val.to_val(&mut scope);
-    handle_result(global.set(scope, val), |()| {})
+    #[cfg(feature = "gc")]
+    {
+        let mut scope = RootScope::new(&mut store);
+        let val = val.to_val(&mut scope);
+        handle_result(global.set(scope, val), |()| {})
+    }
+
+    #[cfg(not(feature = "gc"))]
+    {
+        let val = val.to_val_unscoped(&mut store);
+        handle_result(global.set(&mut store, val), |()| {})
+    }
 }