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Extract copy/restore of first argument in method call.

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This commit is contained in:
Stephen Chung
2020-05-29 18:15:58 +08:00
parent 9616452c00
commit e1242df5c8
5 changed files with 74 additions and 46 deletions
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82
src/engine.rs
View File

@@ -615,33 +615,54 @@ impl Engine {
return Err(Box::new(EvalAltResult::ErrorStackOverflow(pos)));
}
}
let mut this_copy: Dynamic = Default::default();
let mut old_this_ptr: Option<&mut Dynamic> = None;
/// This function replaces the first argument of a method call with a clone copy.
/// This is to prevent a pure function unintentionally consuming the first argument.
fn normalize_first_arg<'a>(
normalize: bool,
this_copy: &mut Dynamic,
old_this_ptr: &mut Option<&'a mut Dynamic>,
args: &mut FnCallArgs<'a>,
) {
// Only do it for method calls with arguments.
if !normalize || args.is_empty() {
return;
}
// Clone the original value.
*this_copy = args[0].clone();
// Replace the first reference with a reference to the clone, force-casting the lifetime.
// Keep the original reference. Must remember to restore it later with `restore_first_arg_of_method_call`.
let this_pointer = mem::replace(
args.get_mut(0).unwrap(),
unsafe_mut_cast_to_lifetime(this_copy),
);
*old_this_ptr = Some(this_pointer);
}
/// This function restores the first argument that was replaced by `normalize_first_arg_of_method_call`.
fn restore_first_arg<'a>(old_this_ptr: Option<&'a mut Dynamic>, args: &mut FnCallArgs<'a>) {
if let Some(this_pointer) = old_this_ptr {
mem::replace(args.get_mut(0).unwrap(), this_pointer);
}
}
// First search in script-defined functions (can override built-in)
if !native_only {
if let Some(fn_def) = lib.get(&hashes.1) {
let mut this_copy: Option<Dynamic>;
let mut this_pointer: Option<&mut Dynamic> = None;
if is_ref && !args.is_empty() {
// Clone the original value. It'll be consumed because the function
// is pure and doesn't know that the first value is a reference (i.e. `is_ref`)
this_copy = Some(args[0].clone());
// Replace the first reference with a reference to the clone, force-casting the lifetime.
// Keep the original reference. Must remember to restore it before existing this function.
this_pointer = Some(mem::replace(
args.get_mut(0).unwrap(),
unsafe_mut_cast_to_lifetime(this_copy.as_mut().unwrap()),
));
}
normalize_first_arg(is_ref, &mut this_copy, &mut old_this_ptr, args);
// Run scripted function
let result =
self.call_script_fn(scope, state, lib, fn_name, fn_def, args, pos, level)?;
// Restore the original reference
if let Some(this_pointer) = this_pointer {
mem::replace(args.get_mut(0).unwrap(), this_pointer);
}
restore_first_arg(old_this_ptr, args);
return Ok((result, false));
}
@@ -654,29 +675,18 @@ impl Engine {
.or_else(|| self.packages.get_fn(hashes.0))
{
// Calling pure function in method-call?
let mut this_copy: Option<Dynamic>;
let mut this_pointer: Option<&mut Dynamic> = None;
if func.is_pure() && is_ref && !args.is_empty() {
// Clone the original value. It'll be consumed because the function
// is pure and doesn't know that the first value is a reference (i.e. `is_ref`)
this_copy = Some(args[0].clone());
// Replace the first reference with a reference to the clone, force-casting the lifetime.
// Keep the original reference. Must remember to restore it before existing this function.
this_pointer = Some(mem::replace(
args.get_mut(0).unwrap(),
unsafe_mut_cast_to_lifetime(this_copy.as_mut().unwrap()),
));
}
normalize_first_arg(
func.is_pure() && is_ref,
&mut this_copy,
&mut old_this_ptr,
args,
);
// Run external function
let result = func.get_native_fn()(args);
// Restore the original reference
if let Some(this_pointer) = this_pointer {
mem::replace(args.get_mut(0).unwrap(), this_pointer);
}
restore_first_arg(old_this_ptr, args);
let result = result.map_err(|err| err.new_position(pos))?;

6
src/module.rs
View File

@@ -544,7 +544,7 @@ impl Module {
/// use rhai::Module;
///
/// let mut module = Module::new();
/// let hash = module.set_fn_3("calc", |x: i64, y: String, z: i64, _w: ()| {
/// let hash = module.set_fn_4("calc", |x: i64, y: String, z: i64, _w: ()| {
/// Ok(x + y.len() as i64 + z)
/// });
/// assert!(module.get_fn(hash).is_some());
@@ -583,7 +583,7 @@ impl Module {
)
}
/// Set a Rust function taking three parameters (the first one mutable) into the module,
/// Set a Rust function taking four parameters (the first one mutable) into the module,
/// returning a hash key.
///
/// If there is a similar existing Rust function, it is replaced.
@@ -594,7 +594,7 @@ impl Module {
/// use rhai::Module;
///
/// let mut module = Module::new();
/// let hash = module.set_fn_3_mut("calc", |x: &mut i64, y: String, z: i64, _w: ()| {
/// let hash = module.set_fn_4_mut("calc", |x: &mut i64, y: String, z: i64, _w: ()| {
/// *x += y.len() as i64 + z; Ok(*x)
/// });
/// assert!(module.get_fn(hash).is_some());