Add support for user JS library code to be able to depend on C functions

emcc.py

@@ -35,6 +35,7 @@
 from enum import Enum, unique, auto
 from subprocess import PIPE
 from urllib.parse import quote
+from tools.deps_info import append_wasm_deps_info
 
 
 import emscripten
@@ -3749,6 +3750,11 @@ def process_libraries(state, linker_inputs):
   # Sort the input list from (order, lib_name) pairs to a flat array in the right order.
   settings.JS_LIBRARIES.sort(key=lambda lib: lib[0])
   settings.JS_LIBRARIES = [lib[1] for lib in settings.JS_LIBRARIES]
+
+  for f in settings.JS_LIBRARIES:
+    wasm_deps = shared.run_js_tool(shared.path_from_root('src/read_wasm_deps.js'), [shared.path_from_root('src', f)], stdout=PIPE)
+    append_wasm_deps_info(json.loads(wasm_deps))
+
   state.link_flags = new_flags
 
 

src/read_wasm_deps.js

@@ -0,0 +1,76 @@
+var fs = require('fs');
+
+function readFile(filename) {
+  return fs.readFileSync(filename).toString();
+}
+
+function include(filename) {
+  eval.call(null, readFile(`${__dirname}/${filename}`));
+}
+
+include('utility.js');
+include('settings.js');
+include('settings_internal.js');
+include('parseTools.js');
+
+// Read all input JS library files into LibraryManager.
+var LibraryManager = { library: {} };
+for(let f of process.argv.slice(2)) {
+  eval(processMacros(preprocess(readFile(f), f)));
+}
+
+// Grab all JS -> JS deps and JS -> C deps from the input files
+const DEPS_SUFFIX = '__deps';
+const WASM_DEPS_SUFFIX = '__wasm_deps';
+
+let jsToJsDeps = {};
+let jsToWasmDeps = {};
+
+for(let s in LibraryManager.library) {
+  if (s.endsWith(DEPS_SUFFIX)) jsToJsDeps[s.substr(0, s.length - DEPS_SUFFIX.length)] = LibraryManager.library[s];
+  else if (s.endsWith(WASM_DEPS_SUFFIX)) jsToWasmDeps[s.substr(0, s.length - WASM_DEPS_SUFFIX.length)] = LibraryManager.library[s];
+}
+
+// Key jsToJsDeps backwards: given a JS function as key, lists all functions that depend on this function.
+let jsToJsBackDeps = {};
+
+for(let depender in jsToJsDeps) {
+  for(let dependee of jsToJsDeps[depender]) {
+    if (!jsToJsBackDeps[dependee]) jsToJsBackDeps[dependee] = [];
+    if (!jsToJsBackDeps[dependee].includes(depender)) jsToJsBackDeps[dependee].push(depender);
+  }
+}
+
+// Appends those elements from array src to array dst that did not yet exist in dst.
+// Operates in-place, returns true if any modifications to array dst were done.
+function appendToArrayIfNotExists(dst, src) {
+  let modified = false;
+  for(let element of src) {
+    if (!dst.includes(element)) {
+      dst.push(element);
+      modified = true;
+    }
+  }
+  return modified;
+}
+
+// Transitively propagate all jsToWasm deps backwards, i.e. if jsFunc1 depends on jsFunc2,
+// and jsFunc2 depends on wasmFunc1, also record jsFunc1 to depend on wasmFunc1.
+// Perform the propagation to a new dictionary to not disturb iteration over jsToWasmDeps.
+let transitiveJsToWasmDeps = {};
+for(let dep in jsToWasmDeps) {
+  const wasmDeps = jsToWasmDeps[dep];
+  let stack = [dep];
+  while(stack.length > 0) {
+    let f = stack.pop();
+    if (!transitiveJsToWasmDeps[f]) transitiveJsToWasmDeps[f] = [];
+    if (appendToArrayIfNotExists(transitiveJsToWasmDeps[f], wasmDeps)) {
+      // Keep going if this append produced some modifications (this check makes sure we don't infinite loop on cycles)
+      if (jsToJsBackDeps[f]) stack = stack.concat(jsToJsBackDeps[f]);
+    }
+  }
+}
+jsToWasmDeps = transitiveJsToWasmDeps;
+
+// Print final output
+console.log(JSON.stringify(transitiveJsToWasmDeps));

src/settings.js

@@ -1947,7 +1947,7 @@ var SPLIT_MODULE = 0;
 //         llvm-nm on all input) and use the map in deps_info.py to determine
 //         the set of additional dependencies.
 // 'all' : Include the full set of possible reverse dependencies.
-// 'none': No reverse dependences will be added by emscriopten. Any reverse
+// 'none': No reverse dependences will be added by emscripten. Any reverse
 //         dependencies will be assumed to be explicitly added to
 //         EXPORTED_FUNCTIONS and deps_info.py will be completely ignored.
 // While 'auto' will produce a minimal set (so is good for code size), 'all'

tests/test_other.py

@@ -11401,3 +11401,29 @@ def test_gmtime_noleak(self):
     # Confirm that gmtime_r does not leak when called in isolation.
     self.emcc_args.append('-fsanitize=leak')
     self.do_other_test('test_gmtime_noleak.c')
+
+  # Tests the use of foo__wasm_deps: ['wasmFunc1', 'wasmFunc2'] from JS library files
+  def test_wasm_deps(self):
+    create_file('lib.js', r'''
+mergeInto(LibraryManager.library, {
+  foo__wasm_deps: ['wasmFunction'],
+  foo: function() {
+    return _wasmFunction();
+  },
+
+  bar__deps: ['foo'],
+  bar: function() {
+    return _foo();
+  }
+});
+''')
+
+    create_file('main.c', r'''
+#include <stdio.h>
+int wasmFunction() { return 492; }
+int bar(void);
+int main() { printf("%d\n", bar()); }
+''')
+
+    self.run_process([EMCC, 'main.c', '--js-library', 'lib.js'])
+    self.assertContained('492', self.run_js('a.out.js'))

tools/deps_info.py

@@ -199,6 +199,11 @@
 }
 
 
+def append_wasm_deps_info(wasm_deps_info):
+  for key, value in wasm_deps_info.items():
+    _deps_info[key] = value
+
+
 def get_deps_info():
   if not settings.EXCEPTION_HANDLING and settings.LINK_AS_CXX:
     _deps_info['__cxa_begin_catch'] = ['__cxa_is_pointer_type']