Fix expansion of "floating" WASM variables in repl/watch + readMemory when WASM memory is SharedArrayBuffer (#2199)

* Fix expansion of "floating" WASM variables in repl/watch + readMemory when WASM memory is SharedArrayBuffer

* Fix flaky test

Author: mikaelwaltersson

src/adapter/dwarf/wasmSymbolProvider.ts

@@ -345,7 +345,7 @@ export interface IWasmSymbols extends IDisposable {
     callFrameId: string,
     position: IPosition,
     expression: string,
-  ): Promise<Cdp.Runtime.RemoteObject | undefined>;
+  ): Promise<IWasmVariableEvaluation>;
 
   /**
    * Gets ranges that should be stepped for the given step kind and location.
@@ -681,9 +681,9 @@ class WasmSymbols extends DecompiledWasmSymbols {
     callFrameId: string,
     position: IPosition,
     expression: string,
-  ): Promise<Cdp.Runtime.RemoteObject | undefined> {
+  ): Promise<IWasmVariableEvaluation> {
     try {
-      const r = await this.worker.rpc.sendMessage(
+      const result = await this.worker.rpc.sendMessage(
         'evaluate',
         expression,
         {
@@ -694,8 +694,7 @@ class WasmSymbols extends DecompiledWasmSymbols {
         this.worker.getStopId(callFrameId),
       );
 
-      // cast since types in dwarf-debugging are slightly different than generated cdp API
-      return (r as Cdp.Runtime.RemoteObject) ?? undefined;
+      return result ? new WasmVariableEvaluation(result, this.worker.rpc) : nullType;
     } catch (e) {
       // errors are expected here if the user tries to evaluate expressions
       // the simple lldb-eval can't handle.

src/adapter/templates/readMemory.ts

@@ -12,7 +12,8 @@ export const readMemory = remoteFunction(function(
   start: number,
   count: number,
 ) {
-  const { buffer, byteLength, byteOffset } = this instanceof ArrayBuffer
+  const { buffer, byteLength, byteOffset } = (this instanceof ArrayBuffer
+      || (typeof SharedArrayBuffer !== 'undefined' && this instanceof SharedArrayBuffer))
     ? new DataView(this)
     : this instanceof WebAssembly.Memory
     ? new DataView(this.buffer)

src/adapter/threads.ts

@@ -524,11 +524,10 @@ export class Thread implements IVariableStoreLocationProvider {
     );
 
     const result = await symbols.evaluate(cfId, position, args.expression);
-    if (result) {
-      return await variables
-        .createFloatingVariable(args.expression, result)
-        .toDap(args.context as PreviewContextType, args.format);
-    }
+
+    return await variables
+      .createFloatingWasmVariable(args.expression, result, root, cfId)
+      .toDap(args.context as PreviewContextType, args.format);
   }
 
   /**

src/adapter/variableStore.ts

@@ -287,6 +287,14 @@ class VariableContext {
     return this.createVariable(Variable, ctx, object);
   }
 
+  public createWasmVariable(
+    ctx: IContextInit,
+    evaluation: IWasmVariableEvaluation,
+    scopeRef: IScopeRef,
+  ) {
+    return this.createVariable(WasmVariable, ctx, evaluation, scopeRef);
+  }
+
   /**
    * Ensures symbols for custom descriptions are available, must be used
    * before getStringProps/getToStringIfCustom
@@ -1432,6 +1440,22 @@ export class VariableStore {
     return ctx.createVariableByType({ name: expression }, value);
   }
 
+  /** Creates a wasm variable not attached to any specific scope. */
+  public createFloatingWasmVariable(
+    expression: string,
+    evaluation: IWasmVariableEvaluation,
+    stackFrame: StackFrame,
+    callFrameId: Cdp.Debugger.CallFrameId,
+  ): IVariable {
+    const ctx = this.createFloatingContext();
+    const scopeRef: IScopeRef = {
+      stackFrame,
+      callFrameId,
+      scopeNumber: 0, // this is only used for setting variables, which wasm doesn't support
+    };
+    return ctx.createWasmVariable({ name: expression }, evaluation, scopeRef);
+  }
+
   /**
    * Returns the variable reference for a complex, object-including output.
    */

src/test/common/cdpTransport.test.ts

@@ -61,7 +61,7 @@ describe('cdp transport', () => {
         b.onMessage(([msg]) => actual.push(msg));
 
         for (let i = 0; i < rawData.length;) {
-          const consume = Math.floor(Math.random() * 20);
+          const consume = 1 + Math.floor(Math.random() * 20);
           const str = rawData.slice(i, i + consume).toString('base64');
           expected.push(str);
           a.send(str);

src/test/wasm/wasm.test.ts

@@ -227,5 +227,19 @@ describe('webassembly', () => {
 
       r.assertLog();
     });
+
+    itIntegrates('does lldb evaluation for structs', async ({ r, context }) => {
+      const p = await prepare(r, context, 'c-with-struct', {
+        source: { path: 'web/dwarf/c-with-struct.c' },
+        breakpoints: [{ line: 11 }],
+      });
+
+      const { threadId } = p.log(await p.dap.once('stopped'));
+      const { id: frameId } = (await p.dap.stackTrace({ threadId })).stackFrames[0];
+
+      await p.logger.evaluateAndLog('(data_t*)data', { params: { frameId }, depth: 3 });
+
+      r.assertLog();
+    });
   });
 });

src/test/wasm/webassembly-dwarf-does-lldb-evaluation-for-structs.txt

@@ -0,0 +1,23 @@
+{
+    allThreadsStopped : false
+    description : Paused on breakpoint
+    reason : breakpoint
+    threadId : <number>
+}
+> result: data_t *
+    > 0x10408: data_t
+        > id: char[12]
+            0: 'H'
+            1: 'e'
+            2: 'l'
+            3: 'l'
+            4: 'o'
+            5: ' '
+            6: 'w'
+            7: 'o'
+            8: 'r'
+            9: 'l'
+            10: 'd'
+            11: '\0'
+        x: 12
+        y: 34

testWorkspace/web/dwarf/c-with-struct.c

@@ -0,0 +1,17 @@
+
+// Compile with:
+// clang -O0 -g -fdebug-compilation-dir=. --target=wasm32-unknown-unknown -nostdlib c-with-struct.c -o c-with-struct.wasm
+typedef struct data_t {
+    char id[12];
+    int x;
+    int y;
+} data_t;
+
+int process(void *data) {
+    return 0; // Break here and evaluate (data_t*)data in the repl interface
+}
+
+int _start() {
+    data_t data = { .id = "Hello world", .x = 12, .y = 34 };
+    return process(&data);
+}

testWorkspace/web/dwarf/c-with-struct.html

@@ -0,0 +1,14 @@
+<!doctype html>
+<html>
+    <head>
+        <title>C with struct</title>
+        <meta charset="utf-8">
+    </head>
+    <body>
+    </body>
+    <script>
+        WebAssembly
+            .instantiateStreaming(fetch('c-with-struct.wasm'))
+            .then(({ instance }) => instance.exports._start());
+    </script>
+</html>