Re-enable preprocessing of pre/post JS file. NFC

This change got reverted in #19006 so this time we make the
preprocessing optional.

This is useful as it allows things like `{{{ POINTER_SIZE }}}`
and `{{{ makeGetValue(..) }}}` to be used in pre/post JS files, just
like they can be in JS library files.

Fixes: #21226

ChangeLog.md

@@ -20,6 +20,12 @@ See docs/process.md for more on how version tagging works.
 
 3.1.54 (in development)
 -----------------------
+- `--pre-js` and `--post-js` files can now opt into being run through the JS
+  preprocessor. This change was oringally landed in  #18525, but it got reverted
+  in #19006.  Now it requires explict opt-in by add `'use preprocessor';` to
+  the JS file.  This is useful as it allows things like `{{{ POINTER_SIZE }}}`
+  and `{{{ makeGetValue(..) }}}` to be used in pre/post JS files, just
+  like they can be in JS library files. (#21227)
 
 3.1.53 - 01/29/24
 -----------------

src/generated_struct_info32.json

@@ -223,6 +223,7 @@
         "EM_PROMISE_MATCH": 1,
         "EM_PROMISE_MATCH_RELEASE": 2,
         "EM_PROMISE_REJECT": 3,
+        "EM_THREAD_STATUS_NUMFIELDS": 7,
         "EM_TIMING_RAF": 1,
         "EM_TIMING_SETIMMEDIATE": 2,
         "EM_TIMING_SETTIMEOUT": 0,

src/generated_struct_info64.json

@@ -223,6 +223,7 @@
         "EM_PROMISE_MATCH": 1,
         "EM_PROMISE_MATCH_RELEASE": 2,
         "EM_PROMISE_REJECT": 3,
+        "EM_THREAD_STATUS_NUMFIELDS": 7,
         "EM_TIMING_RAF": 1,
         "EM_TIMING_SETIMMEDIATE": 2,
         "EM_TIMING_SETTIMEOUT": 0,

src/jsifier.js

@@ -97,6 +97,22 @@ function getTransitiveDeps(symbol) {
   return Array.from(transitiveDeps);
 }
 
+function shouldPreprocess(fileName) {
+  return read(fileName).match(/'use preprocessor';\n/) != null;
+}
+
+function preJS() {
+  let result = '';
+  for (const fileName of PRE_JS_FILES) {
+    if (shouldPreprocess(fileName)) {
+      result += processMacros(preprocess(fileName));
+    } else {
+      result += read(fileName);
+    }
+  }
+  return result;
+}
+
 function runJSify() {
   const libraryItems = [];
   const symbolDeps = {};
@@ -583,15 +599,13 @@ function(${args}) {
     libraryItems.push(JS);
   }
 
-  function includeFile(fileName) {
+  function includeFile(fileName, needsPreprocess = true) {
     print(`// include: ${fileName}`);
-    print(processMacros(preprocess(fileName)));
-    print(`// end include: ${fileName}`);
-  }
-
-  function includeFileRaw(fileName) {
-    print(`// include: ${fileName}`);
-    print(read(fileName));
+    if (needsPreprocess) {
+      print(processMacros(preprocess(fileName)));
+    } else {
+      print(read(fileName));
+    }
     print(`// end include: ${fileName}`);
   }
 
@@ -653,7 +667,7 @@ var proxiedFunctionTable = [
     includeFile(postFile);
 
     for (const fileName of POST_JS_FILES) {
-      includeFileRaw(fileName);
+      includeFile(fileName, shouldPreprocess(fileName));
     }
 
     print('//FORWARDED_DATA:' + JSON.stringify({

src/parseTools.js

@@ -1022,14 +1022,6 @@ function getEntryFunction() {
   return `_${entryFunction}`;
 }
 
-function preJS() {
-  let result = '';
-  for (const fileName of PRE_JS_FILES) {
-    result += read(fileName);
-  }
-  return result;
-}
-
 function formattedMinNodeVersion() {
   var major = MIN_NODE_VERSION / 10000
   var minor = (MIN_NODE_VERSION / 100) % 100

src/struct_info_internal.json

@@ -24,6 +24,12 @@
           "SIGCANCEL"
         ]
     },
+    {
+        "file": "threading_internal.h",
+        "defines": [
+            "EM_THREAD_STATUS_NUMFIELDS"
+        ]
+    },
     {
         "file": "dynlink.h",
         "structs": {

src/threadprofiler.js

@@ -1,3 +1,5 @@
+'use preprocessor';
+
 /**
  * @license
  * Copyright 2015 The Emscripten Authors
@@ -41,7 +43,7 @@ var emscriptenThreadProfiler = {
     }
     for (var i = 0; i < threads.length; ++i) {
       var threadPtr = threads[i];
-      var profilerBlock = Atomics.load(HEAPU32, (threadPtr + 8 /* {{{ C_STRUCTS.pthread.profilerBlock }}}*/) >> 2);
+      var profilerBlock = Atomics.load(HEAPU32, (threadPtr + {{{ C_STRUCTS.pthread.profilerBlock }}}) >> 2);
       var threadName = PThread.getThreadName(threadPtr);
       if (threadName) {
         threadName = `"${threadName}" (${ptrToString(threadPtr)})`;
@@ -69,7 +71,7 @@ var emscriptenThreadProfiler = {
 
     for (var i = 0; i < threads.length; ++i) {
       var threadPtr = threads[i];
-      var profilerBlock = Atomics.load(HEAPU32, (threadPtr + 8 /* {{{ C_STRUCTS.pthread.profilerBlock }}}*/) >> 2);
+      var profilerBlock = Atomics.load(HEAPU32, (threadPtr + {{{ C_STRUCTS.pthread.profilerBlock }}}) >> 2);
       var threadName = PThread.getThreadName(threadPtr);
       if (threadName) {
         threadName = `"${threadName}" (${ptrToString(threadPtr)})`;
@@ -81,11 +83,11 @@ var emscriptenThreadProfiler = {
 
       var threadTimesInStatus = [];
       var totalTime = 0;
-      var offset = profilerBlock + 16/*C_STRUCTS.thread_profiler_block.timeSpentInStatus*/;
-      for (var j = 0; j < 7/*EM_THREAD_STATUS_NUMFIELDS*/; ++j, offset += 8) {
-        threadTimesInStatus.push(Number(getValue(offset, 'double')));
+      var offset = profilerBlock + {{{ C_STRUCTS.thread_profiler_block.timeSpentInStatus }}};
+      for (var j = 0; j < {{{ cDefs.EM_THREAD_STATUS_NUMFIELDS }}}; ++j, offset += 8) {
+        threadTimesInStatus.push({{{ makeGetValue('offset', 0, 'double') }}});
         totalTime += threadTimesInStatus[j];
-        setValue(offset, 0, 'double');
+        {{{ makeSetValue('offset', 0, 0, 'double') }}};
       }
       var recent = '';
       if (threadTimesInStatus[1] > 0) recent += (threadTimesInStatus[1] / totalTime * 100.0).toFixed(1) + '% running. ';

test/test_other.py

@@ -14434,3 +14434,20 @@ def test_uuid(self):
   def test_wasm64_no_asan(self):
     err = self.expect_fail([EMCC, test_file('hello_world.c'), '-sMEMORY64', '-fsanitize=address'])
     self.assertContained('error: MEMORY64 does not yet work with ASAN', err)
+
+  def test_js_preprocess_pre_post(self):
+    create_file('pre.js', '''
+    'use preprocessor';
+    #if ASSERTIONS
+    console.log('assertions enabled')
+    #else
+    console.log('assertions disabled')
+    #endif
+    ''')
+    create_file('post.js', '''
+    'use preprocessor';
+    console.log({{{ POINTER_SIZE }}});
+    ''')
+    self.emcc_args += ['--pre-js', 'pre.js', '--post-js', 'post.js']
+    self.do_runf(test_file('hello_world.c'), 'assertions enabled\n4')
+    self.do_runf(test_file('hello_world.c'), 'assertions disabled\n4', emcc_args=['-sASSERTIONS=0'])