[wasm] Enforce strict ordering of WASM module sections.

test/mjsunit/wasm/wasm-module-builder.js

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 function WasmFunctionBuilder(name, sig_index) {
     this.name = name;
     this.sig_index = sig_index;
     this.exports = [];
 }
 
@@ skipping 131 matching lines @@
 }
 
 WasmModuleBuilder.prototype.toArray = function(debug) {
     // Add header bytes
     var bytes = [];
     bytes = bytes.concat([kWasmH0, kWasmH1, kWasmH2, kWasmH3,
                           kWasmV0, kWasmV1, kWasmV2, kWasmV3]);
 
     var wasm = this;
 
-    // Add memory section
-    if (wasm.memory != undefined) {
-        if (debug) print("emitting memory @ " + bytes.length);
-        emit_section(bytes, kDeclMemory, function(bytes) {
-            emit_varint(bytes, wasm.memory.min);
-            emit_varint(bytes, wasm.memory.max);
-            emit_u8(bytes, wasm.memory.exp ? 1 : 0);
-        });
-    }
-
     // Add signatures section
     if (wasm.signatures.length > 0) {
         if (debug) print("emitting signatures @ " + bytes.length);
         emit_section(bytes, kDeclSignatures, function(bytes) {
             emit_varint(bytes, wasm.signatures.length);
             for (sig of wasm.signatures) {
                 var params = sig.length - 1;
                 emit_varint(bytes, params);
                 for (var j = 0; j < sig.length; j++) {
                     emit_u8(bytes, sig[j]);
                 }
             }
         });
     }
 
     // Add imports section
     if (wasm.imports.length > 0) {
         if (debug) print("emitting imports @ " + bytes.length);
         emit_section(bytes, kDeclImportTable, function(bytes) {
             emit_varint(bytes, wasm.imports.length);
             for (imp of wasm.imports) {
                 emit_varint(bytes, imp.sig_index);
                 emit_string(bytes, imp.module);
                 emit_string(bytes, imp.name || '');
             }
         });
     }
 
-    // Add functions section
+    // Add functions declaractions

[JF, 2016/04/19 15:48:47]

typo

[titzer, 2016/04/20 08:51:24]

Done.

     var names = false;
     var exports = 0;
     if (wasm.functions.length > 0) {
         var has_names = false;
 
         // emit function signatures
         if (debug) print("emitting function sigs @ " + bytes.length);
         emit_section(bytes, kDeclFunctionSignatures, function(bytes) {
             emit_varint(bytes, wasm.functions.length);
             for (func of wasm.functions) {
               has_names = has_names || (func.name != undefined &&
                                         func.name.length > 0);
               exports += func.exports.length;
 
               emit_varint(bytes, func.sig_index);
             }
         });
 
+    }
+
+    // Add function table.
+    if (wasm.function_table.length > 0) {
+        if (debug) print("emitting function table @ " + bytes.length);
+        emit_section(bytes, kDeclFunctionTable, function(bytes) {
+            emit_varint(bytes, wasm.function_table.length);
+            for (index of wasm.function_table) {
+                emit_varint(bytes, index);
+            }
+        });
+    }
+
+    // Add memory section
+    if (wasm.memory != undefined) {
+        if (debug) print("emitting memory @ " + bytes.length);
+        emit_section(bytes, kDeclMemory, function(bytes) {
+            emit_varint(bytes, wasm.memory.min);
+            emit_varint(bytes, wasm.memory.max);
+            emit_u8(bytes, wasm.memory.exp ? 1 : 0);
+        });
+    }
+
+
+    // Add export table.
+    if (exports > 0) {
+        if (debug) print("emitting exports @ " + bytes.length);
+        emit_section(bytes, kDeclExportTable, function(bytes) {
+            emit_varint(bytes, exports);
+            for (func of wasm.functions) {
+                for (exp of func.exports) {
+                    emit_varint(bytes, func.index);
+                    emit_string(bytes, exp);
+                }
+            }
+        });
+    }
+
+    // Add start function section.
+    if (wasm.start_index != undefined) {
+        if (debug) print("emitting start function @ " + bytes.length);
+        emit_section(bytes, kDeclStartFunction, function(bytes) {
+            emit_varint(bytes, wasm.start_index);
+        });
+    }
+
+    // Add function bodies.
+    if (wasm.functions.length > 0) {
         // emit function bodies
         if (debug) print("emitting function bodies @ " + bytes.length);
         emit_section(bytes, kDeclFunctionBodies, function(bytes) {
             emit_varint(bytes, wasm.functions.length);
             for (func of wasm.functions) {
                 // Function body length will be patched later.
                 var local_decls = [];
                 var l = func.locals;
                 if (l != undefined) {
                   var local_decls_count = 0;
@@ skipping 18 matching lines @@
                   emit_u8(header, decl.type);
                 }
 
                 emit_varint(bytes, header.length + func.body.length);
                 emit_bytes(bytes, header);
                 emit_bytes(bytes, func.body);
             }
         });
     }
 
-    // emit function names
-    if (has_names) {
-        if (debug) print("emitting names @ " + bytes.length);
-        emit_section(bytes, kDeclNames, function(bytes) {
-            emit_varint(bytes, wasm.functions.length);
-            for (func of wasm.functions) {
-                var name = func.name == undefined ? "" : func.name;
-               emit_string(bytes, name);
-               emit_u8(bytes, 0);  // local names count == 0
-            }
-        });
-    }
-
-    // Add start function section.
-    if (wasm.start_index != undefined) {
-        if (debug) print("emitting start function @ " + bytes.length);
-        emit_section(bytes, kDeclStartFunction, function(bytes) {
-            emit_varint(bytes, wasm.start_index);
-        });
-    }
-
-    if (wasm.function_table.length > 0) {
-        if (debug) print("emitting function table @ " + bytes.length);
-        emit_section(bytes, kDeclFunctionTable, function(bytes) {
-            emit_varint(bytes, wasm.function_table.length);
-            for (index of wasm.function_table) {
-                emit_varint(bytes, index);
-            }
-        });
-    }
-
-    if (exports > 0) {
-        if (debug) print("emitting exports @ " + bytes.length);
-        emit_section(bytes, kDeclExportTable, function(bytes) {
-            emit_varint(bytes, exports);
-            for (func of wasm.functions) {
-                for (exp of func.exports) {
-                    emit_varint(bytes, func.index);
-                    emit_string(bytes, exp);
-                }
-            }
-        });
-    }
-
+    // Add data segments.
     if (wasm.data_segments.length > 0) {
         if (debug) print("emitting data segments @ " + bytes.length);
         emit_section(bytes, kDeclDataSegments, function(bytes) {
             emit_varint(bytes, wasm.data_segments.length);
             for (seg of wasm.data_segments) {
                 emit_varint(bytes, seg.addr);
                 emit_varint(bytes, seg.data.length);
                 emit_bytes(bytes, seg.data);
             }
         });
     }
 
-    // Emit any explicitly added sections
+    // Add any explicitly added sections
     for (exp of wasm.explicit) {
         if (debug) print("emitting explicit @ " + bytes.length);
         emit_bytes(bytes, exp);
     }
 
+    // Add function names.
+    if (has_names) {
+        if (debug) print("emitting names @ " + bytes.length);
+        emit_section(bytes, kDeclNames, function(bytes) {
+            emit_varint(bytes, wasm.functions.length);
+            for (func of wasm.functions) {
+                var name = func.name == undefined ? "" : func.name;
+               emit_string(bytes, name);
+               emit_u8(bytes, 0);  // local names count == 0
+            }
+        });
+    }
+
     // End the module.
     if (debug) print("emitting end @ " + bytes.length);
     emit_section(bytes, kDeclEnd, function(bytes) {});
 
     return bytes;
 }
 
 WasmModuleBuilder.prototype.toBuffer = function(debug) {
     var bytes = this.toArray(debug);
     var buffer = new ArrayBuffer(bytes.length);
     var view = new Uint8Array(buffer);
     for (var i = 0; i < bytes.length; i++) {
         var val = bytes[i];
         if ((typeof val) == "string") val = val.charCodeAt(0);
         view[i] = val | 0;
     }
     return buffer;
 }
 
 WasmModuleBuilder.prototype.instantiate = function(ffi, memory) {
     var buffer = this.toBuffer();
     if (memory != undefined) {
       return Wasm.instantiateModule(buffer, ffi, memory);
     } else {
       return Wasm.instantiateModule(buffer, ffi);
     }
 }