Make FunctionContext::control fallible

This helps centralize some error reporting and otherwise makes the code a bit more streamlined!
rustwasm · Jan 25, 2019 · 560ff0f · 560ff0f
1 parent 034ddc7
commit 560ff0f
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Showing 2 changed files with 11 additions and 26 deletions.
diff --git a/src/module/functions/local_function/context.rs b/src/module/functions/local_function/context.rs
@@ -165,9 +165,12 @@ impl<'a> FunctionContext<'a> {
         impl_unreachable(&mut self.operands, &mut self.controls, expr);
     }
 
-    pub fn control(&self, n: usize) -> &ControlFrame {
+    pub fn control(&self, n: usize) -> Result<&ControlFrame> {
+        if n >= self.controls.len() {
+            failure::bail!("jump to nonexistent control block");
+        }
         let idx = self.controls.len() - n - 1;
-        &self.controls[idx]
+        Ok(&self.controls[idx])
     }
 
     pub fn add_to_block<E>(&mut self, block: BlockId, expr: E)
@@ -182,7 +185,7 @@ impl<'a> FunctionContext<'a> {
     where
         E: Into<ExprId>,
     {
-        let ctrl = self.control(control_frame);
+        let ctrl = self.control(control_frame).unwrap();
         if ctrl.unreachable.is_some() {
             return;
         }

diff --git a/src/module/functions/local_function/mod.rs b/src/module/functions/local_function/mod.rs
@@ -783,16 +783,10 @@ fn validate_instruction(
                 .context("`br` to out-of-bounds block")?;
 
             let n = relative_depth as usize;
-            if ctx.controls.len() <= n {
-                return Err(ErrorKind::InvalidWasm
-                    .context("attempt to branch to out-of-bounds block")
-                    .into());
-            }
-
-            let expected = ctx.control(n).label_types.clone();
+            let expected = ctx.control(n)?.label_types.clone();
             let args = ctx.pop_operands(&expected)?.into_boxed_slice();
 
-            let to_block = ctx.control(n).block;
+            let to_block = ctx.control(n)?.block;
             let expr = ctx.func.alloc(Br {
                 block: to_block,
                 args,
@@ -805,18 +799,12 @@ fn validate_instruction(
                 .context("`br_if` to out-of-bounds block")?;
 
             let n = relative_depth as usize;
-            if ctx.controls.len() <= n {
-                return Err(ErrorKind::InvalidWasm
-                    .context("attempt to branch to out-of-bounds block")
-                    .into());
-            }
-
             let (_, condition) = ctx.pop_operand_expected(Some(ValType::I32))?;
 
-            let expected = ctx.control(n).label_types.clone();
+            let expected = ctx.control(n)?.label_types.clone();
             let args = ctx.pop_operands(&expected)?.into_boxed_slice();
 
-            let to_block = ctx.control(n).block;
+            let to_block = ctx.control(n)?.block;
             let expr = ctx.func.alloc(BrIf {
                 condition,
                 block: to_block,
@@ -837,13 +825,7 @@ fn validate_instruction(
                 ctx.validation
                     .label(n)
                     .context("`br_table` with out-of-bounds block")?;
-                let n = n as usize;
-                if ctx.controls.len() < n {
-                    return Err(ErrorKind::InvalidWasm
-                        .context("attempt to jump to an out-of-bounds block from a table entry")
-                        .into());
-                }
-                let control = ctx.control(n);
+                let control = ctx.control(n as usize)?;
                 match label_types {
                     None => label_types = Some(&control.label_types),
                     Some(n) => {