Simplify modifyFunction helper function. NFC (#19551)

The name of the function is not important at any of the call sites since
we only use this helper to modify JS library functions, and JS library
functions get their name set explicitly at the top of
`processLibraryFunction`.

Also, rename the function just in case there are external caller of this
function, this will make it clear they need to update their code.

This change was motivated by #19539 where it helps to avoid worrying
about functions names.

Author: sbc100

ChangeLog.md

@@ -28,6 +28,10 @@ See docs/process.md for more on how version tagging works.
   will be included that fail at runtime.  This matches the behaviour of other
   libc functions that we don't implement.  For those that prefer to get a linker
   error we have the `-sALLOW_UNIMPLEMENTED_SYSCALLS` settings. (#19527)
+- The `modifyFunction` helper in `parseTools.js` was renamed to
+  `modifyJSFunction` and its callback function no longer takes the name of the
+  function being modified.  The name is not relevant for JS library functions
+  and can be safely ignored.
 
 3.1.41 - 06/06/23
 -----------------

src/jsifier.js

@@ -112,7 +112,7 @@ function runJSify() {
     // Automatically convert any incoming pointer arguments from BigInt
     // to double (this limits the range to int53).
     // And convert the return value if the function returns a pointer.
-    return modifyFunction(snippet, (name, args, body) => {
+    return modifyJSFunction(snippet, (args, body) => {
       let argLines = args.split('\n');
       argLines = argLines.map((line) => line.split('//')[0]);
       const argNames = argLines.join(' ').split(',').map((name) => name.trim());
@@ -138,7 +138,7 @@ function runJSify() {
         // body in an inner function.
         newArgs = newArgs.join(',');
         return `\
-function ${name}(${args}) {
+function(${args}) {
   var ret = ((${args}) => { ${body} })(${newArgs});
   return BigInt(ret);
 }`;
@@ -147,7 +147,7 @@ function ${name}(${args}) {
       // Otherwise no inner function is needed and we covert the arguments
       // before executing the function body.
       return `\
-function ${name}(${args}) {
+function(${args}) {
 ${argConvertions}
   ${body};
 }`;
@@ -162,17 +162,14 @@ ${argConvertions}
     // uniform.
     snippet = snippet.toString().replace(/\r\n/gm, '\n');
 
-    // name the function; overwrite if it's already named
-    snippet = snippet.replace(/function(?:\s+([^(]+))?\s*\(/, 'function ' + mangled + '(');
-
     if (isStub) {
       return snippet;
     }
 
     // apply LIBRARY_DEBUG if relevant
     if (LIBRARY_DEBUG && !isJsOnlySymbol(symbol)) {
-      snippet = modifyFunction(snippet, (name, args, body) => `\
-function ${name}(${args}) {
+      snippet = modifyJSFunction(snippet, (args, body) => `\
+function(${args}) {
   var ret = (function() { if (runtimeDebug) err("[library call:${mangled}: " + Array.prototype.slice.call(arguments).map(prettyPrint) + "]");
   ${body}
   }).apply(this, arguments);
@@ -189,18 +186,18 @@ function ${name}(${args}) {
         }
         const sync = proxyingMode === 'sync';
         if (PTHREADS) {
-          snippet = modifyFunction(snippet, (name, args, body) => `
-function ${name}(${args}) {
+          snippet = modifyJSFunction(snippet, (args, body) => `
+function(${args}) {
 if (ENVIRONMENT_IS_PTHREAD)
   return proxyToMainThread(${proxiedFunctionTable.length}, ${+sync}${args ? ', ' : ''}${args});
 ${body}
 }\n`);
         } else if (WASM_WORKERS && ASSERTIONS) {
           // In ASSERTIONS builds add runtime checks that proxied functions are not attempted to be called in Wasm Workers
           // (since there is no automatic proxying architecture available)
-          snippet = modifyFunction(snippet, (name, args, body) => `
-function ${name}(${args}) {
-  assert(!ENVIRONMENT_IS_WASM_WORKER, "Attempted to call proxied function '${name}' in a Wasm Worker, but in Wasm Worker enabled builds, proxied function architecture is not available!");
+          snippet = modifyJSFunction(snippet, (args, body) => `
+function(${args}) {
+  assert(!ENVIRONMENT_IS_WASM_WORKER, "Attempted to call proxied function '${mangled}' in a Wasm Worker, but in Wasm Worker enabled builds, proxied function architecture is not available!");
   ${body}
 }\n`);
         }
@@ -437,8 +434,8 @@ function ${name}(${args}) {
       if (isFunction) {
         // Emit the body of a JS library function.
         if ((USE_ASAN || USE_LSAN || UBSAN_RUNTIME) && LibraryManager.library[symbol + '__noleakcheck']) {
-          contentText = modifyFunction(snippet, (name, args, body) => `
-function ${name}(${args}) {
+          contentText = modifyJSFunction(snippet, (args, body) => `
+function(${args}) {
   return withBuiltinMalloc(function() {
     ${body}
   });
@@ -447,6 +444,10 @@ function ${name}(${args}) {
         } else {
           contentText = snippet; // Regular JS function that will be executed in the context of the calling thread.
         }
+        // Give the function the correct (mangled) name. Overwrite it if it's
+        // already named.  This must happen after the last call to
+        // modifyJSFunction which could have changed or removed the name.
+        contentText = contentText.replace(/function(?:\s+([^(]+))?\s*\(/, `function ${mangled}(`);
       } else if (typeof snippet == 'string' && snippet.startsWith(';')) {
         // In JS libraries
         //   foo: ';[code here verbatim]'

src/library.js

@@ -3799,8 +3799,8 @@ function wrapSyscallFunction(x, library, isWasi) {
   // has disabled the filesystem or we have proven some other way that this will
   // not be called in practice, and do not need that code.
   if (!SYSCALLS_REQUIRE_FILESYSTEM && t.includes('FS.')) {
-    t = modifyFunction(t, function(name, args, body) {
-      return 'function ' + name + '(' + args + ') {\n' +
+    t = modifyJSFunction(t, function(args, body) {
+      return `function(${args}) {\n` +
              (ASSERTIONS ? "abort('it should not be possible to operate on streams when !SYSCALLS_REQUIRE_FILESYSTEM');\n" : '') +
              '}';
     });
@@ -3871,8 +3871,8 @@ function wrapSyscallFunction(x, library, isWasi) {
   post = handler + post;
 
   if (pre || post) {
-    t = modifyFunction(t, function(name, args, body) {
-      return `function ${name}(${args}) {\n${pre}${body}${post}}\n`;
+    t = modifyJSFunction(t, function(args, body) {
+      return `function(${args}) {\n${pre}${body}${post}}\n`;
     });
   }
 

src/parseTools.js

@@ -684,26 +684,23 @@ function makeRetainedCompilerSettings() {
 const WASM_PAGE_SIZE = 65536;
 
 // Receives a function as text, and a function that constructs a modified
-// function, to which we pass the parsed-out name, arguments, body, and possible
+// function, to which we pass the parsed-out arguments, body, and possible
 // "async" prefix of the input function. Returns the output of that function.
-function modifyFunction(text, func) {
+function modifyJSFunction(text, func) {
   // Match a function with a name.
   let match = text.match(/^\s*(async\s+)?function\s+([^(]*)?\s*\(([^)]*)\)/);
   let async_;
-  let name;
   let args;
   let rest;
   if (match) {
     async_ = match[1] || '';
-    name = match[2];
     args = match[3];
     rest = text.substr(match[0].length);
   } else {
     // Match a function without a name (we could probably use a single regex
     // for both, but it would be more complex).
     match = text.match(/^\s*(async\s+)?function\(([^)]*)\)/);
     assert(match, 'could not match function ' + text + '.');
-    name = '';
     async_ = match[1] || '';
     args = match[2];
     rest = text.substr(match[0].length);
@@ -712,7 +709,7 @@ function modifyFunction(text, func) {
   assert(bodyStart >= 0);
   const bodyEnd = rest.lastIndexOf('}');
   assert(bodyEnd > 0);
-  return func(name, args, rest.substring(bodyStart + 1, bodyEnd), async_);
+  return func(args, rest.substring(bodyStart + 1, bodyEnd), async_);
 }
 
 function runIfMainThread(text) {

test/other/test_unoptimized_code_size.js.size

@@ -1 +1 @@
-59352
+59349

test/other/test_unoptimized_code_size_no_asserts.js.size

@@ -1 +1 @@
-33004
+33001

test/other/test_unoptimized_code_size_strict.js.size

@@ -1 +1 @@
-58318
+58315