Merge pull request #196 from WebAssembly/spec-start

Fully support start in wasm modules

4 files changed, 94 insertions, 50 deletions

diff --git a/src/binaryen-shell.cpp b/src/binaryen-shell.cpp
index 4c973c50e..d450e4db7 100644
--- a/src/binaryen-shell.cpp
+++ b/src/binaryen-shell.cpp
@@ -242,20 +242,24 @@ static void run_asserts(size_t* i, bool* checked, AllocatingModule* wasm,
                         std::unique_ptr<SExpressionWasmBuilder>* builder,
                         bool print_before, bool print_after,
                         Name entry) {
-  auto interface = new ShellExternalInterface();
-  auto instance = new ModuleInstance(*wasm, interface);
-  if (entry.is() > 0) {
-    Function* function = wasm->functionsMap[entry];
-    if (!function) {
-      std::cerr << "Unknown entry " << entry << std::endl;
-    } else {
-      ModuleInstance::LiteralList arguments;
-      for (NameType param : function->params) {
-        arguments.push_back(Literal(param.type));
-      }
-      try {
-        instance->callExport(entry, arguments);
-      } catch (ExitException& x) {
+  ShellExternalInterface* interface = nullptr;
+  ModuleInstance* instance = nullptr;
+  if (wasm) {
+    interface = new ShellExternalInterface();
+    instance = new ModuleInstance(*wasm, interface);
+    if (entry.is() > 0) {
+      Function* function = wasm->functionsMap[entry];
+      if (!function) {
+        std::cerr << "Unknown entry " << entry << std::endl;
+      } else {
+        ModuleInstance::LiteralList arguments;
+        for (NameType param : function->params) {
+          arguments.push_back(Literal(param.type));
+        }
+        try {
+          instance->callExport(entry, arguments);
+        } catch (ExitException& x) {
+        }
       }
     }
   }
@@ -280,12 +284,14 @@ static void run_asserts(size_t* i, bool* checked, AllocatingModule* wasm,
         std::cout << wasm;
       }
       bool invalid = false;
+      std::unique_ptr<SExpressionWasmBuilder> builder;
       try {
-        *builder = std::unique_ptr<SExpressionWasmBuilder>(
-            new SExpressionWasmBuilder(wasm, *curr[1], [&]() {
-              invalid = true;
-              throw ParseException();
-            }));
+        builder = std::unique_ptr<SExpressionWasmBuilder>(
+          new SExpressionWasmBuilder(wasm, *curr[1], [&]() {
+            invalid = true;
+            throw ParseException();
+          })
+        );
       } catch (const ParseException& e) {
         invalid = true;
       }
@@ -295,10 +301,12 @@ static void run_asserts(size_t* i, bool* checked, AllocatingModule* wasm,
       }
       assert(invalid);
     } else if (id == INVOKE) {
+      assert(wasm);
       Invocation invocation(curr, instance, *builder->get());
       invocation.invoke();
     } else {
       // an invoke test
+      assert(wasm);
       bool trapped = false;
       Literal result;
       try {
@@ -390,39 +398,45 @@ int main(int argc, const char* argv[]) {
   bool checked = false;
   size_t i = 0;
   while (i < root.size()) {
-    if (options.debug) std::cerr << "parsing s-expressions to wasm...\n";
-    AllocatingModule wasm;
-    std::unique_ptr<SExpressionWasmBuilder> builder(
-        new SExpressionWasmBuilder(wasm, *root[i], [&]() { abort(); }, options.debug));
-    i++;
-
-    if (print_before) {
-      Colors::bold(std::cout);
-      std::cerr << "printing before:\n";
-      Colors::normal(std::cout);
-      std::cout << wasm;
-    }
+    Element& curr = *root[i];
+    IString id = curr[0]->str();
+    if (id == MODULE) {
+      if (options.debug) std::cerr << "parsing s-expressions to wasm...\n";
+      AllocatingModule wasm;
+      std::unique_ptr<SExpressionWasmBuilder> builder(
+          new SExpressionWasmBuilder(wasm, *root[i], [&]() { abort(); }, options.debug));
+      i++;
+
+      if (print_before) {
+        Colors::bold(std::cout);
+        std::cerr << "printing before:\n";
+        Colors::normal(std::cout);
+        std::cout << wasm;
+      }
 
-    MixedArena moreModuleAllocations;
+      MixedArena moreModuleAllocations;
 
-    if (passes.size() > 0) {
-      if (options.debug) std::cerr << "running passes...\n";
-      PassRunner passRunner(&moreModuleAllocations);
-      for (auto& passName : passes) {
-        passRunner.add(passName);
+      if (passes.size() > 0) {
+        if (options.debug) std::cerr << "running passes...\n";
+        PassRunner passRunner(&moreModuleAllocations);
+        for (auto& passName : passes) {
+          passRunner.add(passName);
+        }
+        passRunner.run(&wasm);
       }
-      passRunner.run(&wasm);
-    }
 
-    if (print_after) {
-      Colors::bold(std::cout);
-      std::cerr << "printing after:\n";
-      Colors::normal(std::cout);
-      std::cout << wasm;
+      if (print_after) {
+        Colors::bold(std::cout);
+        std::cerr << "printing after:\n";
+        Colors::normal(std::cout);
+        std::cout << wasm;
+      }
+      run_asserts(&i, &checked, &wasm, &root, &builder, print_before,
+                  print_after, entry);
+    } else {
+      run_asserts(&i, &checked, nullptr, &root, nullptr, print_before,
+            print_after, entry);
     }
-
-    run_asserts(&i, &checked, &wasm, &root, &builder, print_before,
-                print_after, entry);
   }
 
   if (checked) {
diff --git a/src/wasm-binary.h b/src/wasm-binary.h
index 2c884a4f5..b1db70a97 100644
--- a/src/wasm-binary.h
+++ b/src/wasm-binary.h
@@ -155,7 +155,8 @@ enum Section {
   Functions = 2,
   DataSegments = 4,
   FunctionTable = 5,
-  End = 6
+  End = 6,
+  Start = 7
 };
 
 enum FunctionEntry {
@@ -380,6 +381,7 @@ public:
   }
 
   void write() {
+    writeStart();
     writeMemory();
     writeSignatures();
     writeFunctions();
@@ -389,6 +391,13 @@ public:
     finishUp();
   }
 
+  void writeStart() {
+    if (!wasm->start.is()) return;
+    if (debug) std::cerr << "== writeStart" << std::endl;
+    o << int8_t(BinaryConsts::Start);
+    emitString(wasm->start.str);
+  }
+
   void writeMemory() {
     if (wasm->memory.max == 0) return;
     if (debug) std::cerr << "== writeMemory" << std::endl;
@@ -980,6 +989,7 @@ public:
       }
 
       switch (section) {
+        case BinaryConsts::Start:         readStart(); break;
         case BinaryConsts::Memory:        readMemory(); break;
         case BinaryConsts::Signatures:    readSignatures(); break;
         case BinaryConsts::Functions:     readFunctions(); break;
@@ -1082,6 +1092,11 @@ public:
     assert(x == y);
   }
 
+  void readStart() {
+    if (debug) std::cerr << "== readStart" << std::endl;
+    wasm.start = getString();
+  }
+
   void readMemory() {
     if (debug) std::cerr << "== readMemory" << std::endl;
     size_t initial = getInt8();
diff --git a/src/wasm-interpreter.h b/src/wasm-interpreter.h
index 267615a55..59e42783d 100644
--- a/src/wasm-interpreter.h
+++ b/src/wasm-interpreter.h
@@ -100,6 +100,10 @@ public:
   ModuleInstance(Module& wasm, ExternalInterface* externalInterface) : wasm(wasm), externalInterface(externalInterface) {
     memorySize = wasm.memory.initial;
     externalInterface->init(wasm);
+    if (wasm.start.is()) {
+      LiteralList arguments;
+      callFunction(wasm.start, arguments);
+    }
   }
 
   Literal callExport(IString name, LiteralList& arguments) {
diff --git a/src/wasm-validator.h b/src/wasm-validator.h
index fad33a081..04493bb5b 100644
--- a/src/wasm-validator.h
+++ b/src/wasm-validator.h
@@ -104,6 +104,7 @@ public:
     shouldBeFalse(top > curr->initial);
   }
   void visitModule(Module *curr) {
+    // exports
     for (auto& exp : curr->exports) {
       Name name = exp->name;
       bool found = false;
@@ -115,6 +116,14 @@ public:
       }
       shouldBeTrue(found);
     }
+    // start
+    if (curr->start.is()) {
+      auto iter = curr->functionsMap.find(curr->start);
+      if (shouldBeTrue(iter != curr->functionsMap.end())) {
+        auto func = iter->second;
+        shouldBeTrue(func->params.size() == 0); // must be nullary
+      }
+    }
   }
 
 private:
@@ -135,11 +144,13 @@ private:
 
   // helpers
 
-  void shouldBeTrue(bool result) {
+  bool shouldBeTrue(bool result) {
     if (!result) valid = false;
+    return result;
   }
-  void shouldBeFalse(bool result) {
+  bool shouldBeFalse(bool result) {
     if (result) valid = false;
+    return result;
   }
 
   void validateAlignment(size_t align) {