src/jsifier.js - external/github.com/emscripten-core/emscripten.git - Git at Google

 /**
  * @license
  * Copyright 2010 The Emscripten Authors
  * SPDX-License-Identifier: MIT
  */

 //"use strict";

 // Convert analyzed data to javascript. Everything has already been calculated
 // before this stage, which just does the final conversion to JavaScript.

 var addedLibraryItems = {};

 // Some JS-implemented library functions are proxied to be called on the main browser thread, if the Emscripten runtime is executing in a Web Worker.
 // Each such proxied function is identified via an ordinal number (this is not the same namespace as function pointers in general).
 var proxiedFunctionTable = ["null" /* Reserve index 0 for an undefined function*/];

 // Used internally. set when there is a main() function.
 // Also set when in a linkable module, as the main() function might
 // arrive from a dynamically-linked library, and not necessarily
 // the current compilation unit.
 // Also set for STANDALONE_WASM since the _start function is needed to call
 // static ctors, even if there is no user main.
 var HAS_MAIN = ('_main' in IMPLEMENTED_FUNCTIONS) || MAIN_MODULE || STANDALONE_WASM;

 // Mangles the given C/JS side function name to assembly level function name (adds an underscore)
 function mangleCSymbolName(f) {
   return f[0] == '$' ? f.substr(1) : '_' + f;
 }

 // Splits out items that pass filter. Returns also the original sans the filtered
 function splitter(array, filter) {
   var splitOut = array.filter(filter);
   var leftIn = array.filter((x) => !filter(x));
   return { leftIn: leftIn, splitOut: splitOut };
 }

 // Functions that start with '$' should not be exported to the wasm module.
 // They are intended to be exclusive to JS code only.
 function isJsOnlyIdentifier(ident) {
   return ident[0] == '$';
 }

 function escapeJSONKey(x) {
   if (/^[\d\w_]+$/.exec(x) || x[0] === '"' || x[0] === "'") return x;
   assert(x.indexOf("'") < 0, 'cannot have internal single quotes in keys: ' + x);
   return "'" + x + "'";
 }

 function stringifyWithFunctions(obj) {
   if (typeof obj === 'function') return obj.toString();
   if (obj === null || typeof obj !== 'object') return JSON.stringify(obj);
   if (Array.isArray(obj)) {
     return '[' + obj.map(stringifyWithFunctions).join(',') + ']';
   } else {
     return '{' + keys(obj).map((key) => escapeJSONKey(key) + ':' + stringifyWithFunctions(obj[key])).join(',') + '}';
   }
 }

 // JSifier
 function JSify(data, functionsOnly) {
   var mainPass = !functionsOnly;

   var itemsDict = { type: [], GlobalVariableStub: [], functionStub: [], function: [], GlobalVariable: [], GlobalVariablePostSet: [] };

   if (mainPass) {
     // Add additional necessary items for the main pass. We can now do this since types are parsed (types can be used through
     // generateStructInfo in library.js)

     LibraryManager.load();

     var libFuncsToInclude;
     if (INCLUDE_FULL_LIBRARY) {
       libFuncsToInclude = MAIN_MODULE ? DEFAULT_LIBRARY_FUNCS_TO_INCLUDE.slice(0) : [];
       for (var key in LibraryManager.library) {
         if (!isJsLibraryConfigIdentifier(key)) {
           libFuncsToInclude.push(key);
         }
       }
     } else {
       libFuncsToInclude = DEFAULT_LIBRARY_FUNCS_TO_INCLUDE;
     }
     libFuncsToInclude.forEach((ident) => {
       data.functionStubs.push({
         identOrig: ident,
         identMangled: mangleCSymbolName(ident)
       });
     });
   }

   function processLibraryFunction(snippet, ident, finalName) {
     // It is possible that when printing the function as a string on Windows, the js interpreter we are in returns the string with Windows
     // line endings \r\n. This is undesirable, since line endings are managed in the form \n in the output for binary file writes, so
     // make sure the endings are 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 ' + finalName + '(');

     // apply LIBRARY_DEBUG if relevant
     if (LIBRARY_DEBUG) {
       snippet = modifyFunction(snippet, (name, args, body) => {
         return 'function ' + name + '(' + args + ') {\n' +
                'var ret = (function() { if (runtimeDebug) err("[library call:' + finalName + ': " + Array.prototype.slice.call(arguments).map(prettyPrint) + "]");\n' +
                 body +
                 '}).apply(this, arguments); if (runtimeDebug && typeof ret !== "undefined") err("  [     return:" + prettyPrint(ret)); return ret; \n}\n';
       });
     }
     return snippet;
   }

   // functionStub
   function functionStubHandler(item) {
     // In LLVM, exceptions generate a set of functions of form __cxa_find_matching_catch_1(), __cxa_find_matching_catch_2(), etc.
     // where the number specifies the number of arguments. In Emscripten, route all these to a single function '__cxa_find_matching_catch'
     // that variadically processes all of these functions using JS 'arguments' object.
     if (item.identMangled.startsWith('___cxa_find_matching_catch_')) {
       if (DISABLE_EXCEPTION_THROWING) {
         error('DISABLE_EXCEPTION_THROWING was set (likely due to -fno-exceptions), which means no C++ exception throwing support code is linked in, but exception catching code appears. Either do not set DISABLE_EXCEPTION_THROWING (if you do want exception throwing) or compile all source files with -fno-except (so that no exceptions support code is required); also make sure DISABLE_EXCEPTION_CATCHING is set to the right value - if you want exceptions, it should be off, and vice versa.');
         return;
       }
       var num = +item.identMangled.split('_').slice(-1)[0];
       addCxaCatch(num);
       // Continue, with the code below emitting the proper JavaScript based on
       // what we just added to the library.
     }

     function addFromLibrary(item, dependent) {
       // dependencies can be JS functions, which we just run
       if (typeof item == 'function') return item();

       var ident = item.identOrig;
       var finalName = item.identMangled;

       if (ident in addedLibraryItems) return '';
       addedLibraryItems[ident] = true;

       // don't process any special identifiers. These are looked up when processing the base name of the identifier.
       if (isJsLibraryConfigIdentifier(ident)) {
         return '';
       }

       // if the function was implemented in compiled code, we just need to export it so we can reach it from JS
       if (finalName in IMPLEMENTED_FUNCTIONS) {
         EXPORTED_FUNCTIONS[finalName] = 1;
         // stop here: we don't need to add anything from our js libraries, not even deps, compiled code is on it
         return '';
       }

       // Don't replace implemented functions with library ones (which can happen when we add dependencies).
       // Note: We don't return the dependencies here. Be careful not to end up where this matters
       if (finalName in Functions.implementedFunctions) return '';

       var noExport = false;

       if (!LibraryManager.library.hasOwnProperty(ident)) {
         if (!(finalName in IMPLEMENTED_FUNCTIONS) && !LINKABLE) {
           var msg = 'undefined symbol: ' + ident;
           if (dependent) msg += ' (referenced by ' + dependent + ')';
           if (ERROR_ON_UNDEFINED_SYMBOLS) {
             error(msg);
             if (!LLD_REPORT_UNDEFINED) {
               warnOnce('Link with `-s LLD_REPORT_UNDEFINED` to get more information on undefined symbols');
             }
             warnOnce('To disable errors for undefined symbols use `-s ERROR_ON_UNDEFINED_SYMBOLS=0`')
             warnOnce(finalName + ' may need to be added to EXPORTED_FUNCTIONS if it arrives from a system library')
           } else if (VERBOSE || WARN_ON_UNDEFINED_SYMBOLS) {
             warn(msg);
           }
           if (ident === 'main' && STANDALONE_WASM) {
             warn('To build in STANDALONE_WASM mode without a main(), use emcc --no-entry');
           }
         }
         if (!RELOCATABLE) {
           // emit a stub that will fail at runtime
           LibraryManager.library[ident] = new Function("err('missing function: " + ident + "'); abort(-1);");
           // We have already warned/errored about this function, so for the purposes of Closure use, mute all type checks
           // regarding this function, marking ot a variadic function that can take in anything and return anything.
           // (not useful to warn/error multiple times)
           LibraryManager.library[ident + '__docs'] = '/** @type {function(...*):?} */';
         } else {
           var target = "Module['" + finalName + "']";
           var assertion = '';
           if (ASSERTIONS) {
             var what = 'function';
             assertion += 'if (!' + target + ') abort("external symbol \'' + ident + '\' is missing. perhaps a side module was not linked in? if this function was expected to arrive from a system library, try to build the MAIN_MODULE with EMCC_FORCE_STDLIBS=1 in the environment");\n';

           }
           var functionBody = assertion + "return " + target + ".apply(null, arguments);";
           LibraryManager.library[ident] = new Function(functionBody);
           noExport = true;
         }
       }

       var original = LibraryManager.library[ident];
       var snippet = original;
       var redirectedIdent = null;
       var deps = LibraryManager.library[ident + '__deps'] || [];
       if (!Array.isArray(deps)) {
         error('JS library directive ' + ident + '__deps=' + deps.toString() + ' is of type ' + typeof deps + ', but it should be an array!');
         return;
       }
       deps.forEach((dep) => {
         if (typeof snippet === 'string' && !(dep in LibraryManager.library)) warn('missing library dependency ' + dep + ', make sure you are compiling with the right options (see #if in src/library*.js)');
       });
       var isFunction = false;

       if (typeof snippet === 'string') {
         if (snippet[0] != '=') {
           var target = LibraryManager.library[snippet];
           if (target) {
             // Redirection for aliases. We include the parent, and at runtime make ourselves equal to it.
             // This avoid having duplicate functions with identical content.
             redirectedIdent = snippet;
             deps.push(snippet);
             snippet = mangleCSymbolName(snippet);
           }
           // In asm, we need to know about library functions. If there is a target, though, then no
           // need to consider this a library function - we will call directly to it anyhow
           if (!redirectedIdent && (typeof target == 'function')) {
             Functions.libraryFunctions[finalName] = 1;
           }
         }
       } else if (typeof snippet === 'object') {
         snippet = stringifyWithFunctions(snippet);
       } else if (typeof snippet === 'function') {
         isFunction = true;
         snippet = processLibraryFunction(snippet, ident, finalName);
         if (!isJsOnlyIdentifier(ident[0])) {
           Functions.libraryFunctions[finalName] = 1;
         }
       }

       // If a JS library item specifies xxx_import: true, then explicitly mark that symbol to be exported
       // to wasm module.
       if (LibraryManager.library[ident + '__import']) {
         Functions.libraryFunctions[finalName] = 1;
       }

       if (ONLY_CALC_JS_SYMBOLS)
         return '';

       var postsetId = ident + '__postset';
       var postset = LibraryManager.library[postsetId];
       if (postset) {
         // A postset is either code to run right now, or some text we should emit.
         // If it's code, it may return some text to emit as well.
         if (typeof postset === 'function') {
           postset = postset();
         }
         if (postset && !addedLibraryItems[postsetId]) {
           addedLibraryItems[postsetId] = true;
           itemsDict.GlobalVariablePostSet.push({
             JS: postset + ';'
           });
         }
       }

       if (redirectedIdent) {
         deps = deps.concat(LibraryManager.library[redirectedIdent + '__deps'] || []);
       }
       // In asm, dependencies implemented in C might be needed by JS library functions.
       // We don't know yet if they are implemented in C or not. To be safe, export such
       // special cases.
       [LIBRARY_DEPS_TO_AUTOEXPORT].forEach((special) => {
         deps.forEach((dep) => {
           if (dep == special && !EXPORTED_FUNCTIONS[dep]) {
             EXPORTED_FUNCTIONS[dep] = 1;
           }
         });
       });
       if (VERBOSE) {
         printErr('adding ' + finalName + ' and deps ' + deps + ' : ' + (snippet + '').substr(0, 40));
       }
       var identDependents = ident + "__deps: ['" + deps.join("','")+"']";
       function addDependency(dep) {
         if (typeof dep !== 'function') {
           dep = {identOrig: dep, identMangled: mangleCSymbolName(dep)};
         }
         return addFromLibrary(dep, identDependents + ', referenced by ' + dependent);
       }
       var depsText = (deps ? deps.map(addDependency).filter((x) => x != '').join('\n') + '\n' : '');
       var contentText;
       if (isFunction) {
         // Emit the body of a JS library function.
         var proxyingMode = LibraryManager.library[ident + '__proxy'];
         if (USE_PTHREADS && proxyingMode) {
           if (proxyingMode !== 'sync' && proxyingMode !== 'async') {
             throw 'Invalid proxyingMode ' + ident + '__proxy: \'' + proxyingMode + '\' specified!';
           }
           var sync = proxyingMode === 'sync';
           assert(typeof original === 'function');
           contentText = modifyFunction(snippet, (name, args, body) => {
             return 'function ' + name + '(' + args + ') {\n' +
                    'if (ENVIRONMENT_IS_PTHREAD) return _emscripten_proxy_to_main_thread_js(' + proxiedFunctionTable.length + ', ' + (+sync) + (args ? ', ' : '') + args + ');\n' + body + '}\n';
           });
           proxiedFunctionTable.push(finalName);
         } else {
           contentText = snippet; // Regular JS function that will be executed in the context of the calling thread.
         }
       } else if (typeof snippet === 'string' && snippet.indexOf(';') == 0) {
         // In JS libraries
         //   foo: ';[code here verbatim]'
         //  emits
         //   'var foo;[code here verbatim];'
         contentText = 'var ' + finalName + snippet;
         if (snippet[snippet.length-1] != ';' && snippet[snippet.length-1] != '}') contentText += ';';
       } else {
         // In JS libraries
         //   foo: '=[value]'
         //  emits
         //   'var foo = [value];'
         if (typeof snippet === 'string' && snippet[0] == '=') snippet = snippet.substr(1);
         contentText = 'var ' + finalName + '=' + snippet + ';';
       }
       var sig = LibraryManager.library[ident + '__sig'];
       // asm module exports are done in emscripten.py, after the asm module is ready. Here
       // we also export library methods as necessary.
       if ((EXPORT_ALL || (finalName in EXPORTED_FUNCTIONS)) && !noExport) {
         contentText += '\nModule["' + finalName + '"] = ' + finalName + ';';
       }
       if (MAIN_MODULE && sig) {
         contentText += '\n' + finalName + '.sig = \'' + sig + '\';';
       }

       var commentText = '';
       if (LibraryManager.library[ident + '__docs']) {
         commentText = LibraryManager.library[ident + '__docs'] + '\n';
       }

       return depsText + commentText + contentText;
     }

     itemsDict.functionStub.push(item);
     item.JS = addFromLibrary(item, 'top-level compiled C/C++ code');
   }

   // Final combiner

   function finalCombiner() {
     var splitPostSets = splitter(itemsDict.GlobalVariablePostSet, (x) => x.ident && x.dependencies);
     itemsDict.GlobalVariablePostSet = splitPostSets.leftIn;
     var orderedPostSets = splitPostSets.splitOut;

     var limit = orderedPostSets.length * orderedPostSets.length;
     for (var i = 0; i < orderedPostSets.length; i++) {
       for (var j = i+1; j < orderedPostSets.length; j++) {
         if (orderedPostSets[j].ident in orderedPostSets[i].dependencies) {
           var temp = orderedPostSets[i];
           orderedPostSets[i] = orderedPostSets[j];
           orderedPostSets[j] = temp;
           i--;
           limit--;
           assert(limit > 0, 'Could not sort postsets!');
           break;
         }
       }
     }

     itemsDict.GlobalVariablePostSet = itemsDict.GlobalVariablePostSet.concat(orderedPostSets);

     //

     if (!mainPass) {
       var generated = itemsDict.function.concat(itemsDict.type).concat(itemsDict.GlobalVariableStub).concat(itemsDict.GlobalVariable);
       print(generated.map((item) => item.JS).join('\n'));
       return;
     }

     var shellFile = SHELL_FILE ? SHELL_FILE : (MINIMAL_RUNTIME ? 'shell_minimal.js' : 'shell.js');

     var shellParts = read(shellFile).split('{{BODY}}');
     print(processMacros(preprocess(shellParts[0], shellFile)));
     var pre;
     if (MINIMAL_RUNTIME) {
       pre = processMacros(preprocess(read('preamble_minimal.js'), 'preamble_minimal.js'));
     } else {
       pre = processMacros(preprocess(read('support.js'), 'support.js')) +
             processMacros(preprocess(read('preamble.js'), 'preamble.js'));
     }
     print(pre);

     // Print out global variables and postsets TODO: batching
     var legalizedI64sDefault = legalizedI64s;
     legalizedI64s = false;

     var globalsData = {functionStubs: []}
     JSify(globalsData, true);
     globalsData = null;

     var generated = itemsDict.functionStub.concat(itemsDict.GlobalVariablePostSet);
     generated.forEach((item) => print(indentify(item.JS || '', 2)));

     legalizedI64s = legalizedI64sDefault;

     if (USE_PTHREADS) {
       print('\n // proxiedFunctionTable specifies the list of functions that can be called either synchronously or asynchronously from other threads in postMessage()d or internally queued events. This way a pthread in a Worker can synchronously access e.g. the DOM on the main thread.')
       print('\nvar proxiedFunctionTable = [' + proxiedFunctionTable.join() + '];\n');
     }

     if (!MINIMAL_RUNTIME) {
       print('var ASSERTIONS = ' + !!ASSERTIONS + ';\n');

       print(preprocess(read('arrayUtils.js')));
     }

     if (SUPPORT_BASE64_EMBEDDING && !MINIMAL_RUNTIME) {
       print(preprocess(read('base64Utils.js')));
     }

     if (abortExecution) throw Error('Aborting compilation due to previous errors');

     // This is the main 'post' pass. Print out the generated code that we have here, together with the
     // rest of the output that we started to print out earlier (see comment on the
     // "Final shape that will be created").
     print('// EMSCRIPTEN_END_FUNCS\n');

     if (HEADLESS) {
       print('if (!ENVIRONMENT_IS_WEB) {');
       print(read('headlessCanvas.js'));
       print('\n');
       print(read('headless.js').replace("'%s'", "'http://emscripten.org'").replace("'?%s'", "''").replace("'?%s'", "'/'").replace('%s,', 'null,').replace('%d', '0'));
       print('}');
     }
     if (PROXY_TO_WORKER) {
       print('if (ENVIRONMENT_IS_WORKER) {\n');
       print(read('webGLWorker.js'));
       print(processMacros(preprocess(read('proxyWorker.js'), 'proxyWorker.js')));
       print('}');
     }
     if (DETERMINISTIC) {
       print(read('deterministic.js'));
     }

     var postFile = MINIMAL_RUNTIME ? 'postamble_minimal.js' : 'postamble.js';
     var post = processMacros(preprocess(read(postFile), postFile));
     print(post);

     var shellParts = read(shellFile).split('{{BODY}}');
     print(processMacros(preprocess(shellParts[1], shellFile)));

     PassManager.serialize();
   }

   // Data

   if (mainPass) {
     data.functionStubs.forEach(functionStubHandler);
   }

   finalCombiner();
 }
	/**
	* @license
	* Copyright 2010 The Emscripten Authors
	* SPDX-License-Identifier: MIT
	*/

	//"use strict";

	// Convert analyzed data to javascript. Everything has already been calculated
	// before this stage, which just does the final conversion to JavaScript.

	var addedLibraryItems = {};

	// Some JS-implemented library functions are proxied to be called on the main browser thread, if the Emscripten runtime is executing in a Web Worker.
	// Each such proxied function is identified via an ordinal number (this is not the same namespace as function pointers in general).
	var proxiedFunctionTable = ["null" /* Reserve index 0 for an undefined function*/];

	// Used internally. set when there is a main() function.
	// Also set when in a linkable module, as the main() function might
	// arrive from a dynamically-linked library, and not necessarily
	// the current compilation unit.
	// Also set for STANDALONE_WASM since the _start function is needed to call
	// static ctors, even if there is no user main.
	var HAS_MAIN = ('_main' in IMPLEMENTED_FUNCTIONS) \|\| MAIN_MODULE \|\| STANDALONE_WASM;

	// Mangles the given C/JS side function name to assembly level function name (adds an underscore)
	function mangleCSymbolName(f) {
	return f[0] == '$' ? f.substr(1) : '_' + f;
	}

	// Splits out items that pass filter. Returns also the original sans the filtered
	function splitter(array, filter) {
	var splitOut = array.filter(filter);
	var leftIn = array.filter((x) => !filter(x));
	return { leftIn: leftIn, splitOut: splitOut };
	}

	// Functions that start with '$' should not be exported to the wasm module.
	// They are intended to be exclusive to JS code only.
	function isJsOnlyIdentifier(ident) {
	return ident[0] == '$';
	}

	function escapeJSONKey(x) {
	if (/^[\d\w_]+$/.exec(x) \|\| x[0] === '"' \|\| x[0] === "'") return x;
	assert(x.indexOf("'") < 0, 'cannot have internal single quotes in keys: ' + x);
	return "'" + x + "'";
	}

	function stringifyWithFunctions(obj) {
	if (typeof obj === 'function') return obj.toString();
	if (obj === null \|\| typeof obj !== 'object') return JSON.stringify(obj);
	if (Array.isArray(obj)) {
	return '[' + obj.map(stringifyWithFunctions).join(',') + ']';
	} else {
	return '{' + keys(obj).map((key) => escapeJSONKey(key) + ':' + stringifyWithFunctions(obj[key])).join(',') + '}';
	}
	}

	// JSifier
	function JSify(data, functionsOnly) {
	var mainPass = !functionsOnly;

	var itemsDict = { type: [], GlobalVariableStub: [], functionStub: [], function: [], GlobalVariable: [], GlobalVariablePostSet: [] };

	if (mainPass) {
	// Add additional necessary items for the main pass. We can now do this since types are parsed (types can be used through
	// generateStructInfo in library.js)

	LibraryManager.load();

	var libFuncsToInclude;
	if (INCLUDE_FULL_LIBRARY) {
	libFuncsToInclude = MAIN_MODULE ? DEFAULT_LIBRARY_FUNCS_TO_INCLUDE.slice(0) : [];
	for (var key in LibraryManager.library) {
	if (!isJsLibraryConfigIdentifier(key)) {
	libFuncsToInclude.push(key);
	}
	}
	} else {
	libFuncsToInclude = DEFAULT_LIBRARY_FUNCS_TO_INCLUDE;
	}
	libFuncsToInclude.forEach((ident) => {
	data.functionStubs.push({
	identOrig: ident,
	identMangled: mangleCSymbolName(ident)
	});
	});
	}

	function processLibraryFunction(snippet, ident, finalName) {
	// It is possible that when printing the function as a string on Windows, the js interpreter we are in returns the string with Windows
	// line endings \r\n. This is undesirable, since line endings are managed in the form \n in the output for binary file writes, so
	// make sure the endings are 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 ' + finalName + '(');

	// apply LIBRARY_DEBUG if relevant
	if (LIBRARY_DEBUG) {
	snippet = modifyFunction(snippet, (name, args, body) => {
	return 'function ' + name + '(' + args + ') {\n' +
	'var ret = (function() { if (runtimeDebug) err("[library call:' + finalName + ': " + Array.prototype.slice.call(arguments).map(prettyPrint) + "]");\n' +
	body +
	'}).apply(this, arguments); if (runtimeDebug && typeof ret !== "undefined") err(" [ return:" + prettyPrint(ret)); return ret; \n}\n';
	});
	}
	return snippet;
	}

	// functionStub
	function functionStubHandler(item) {
	// In LLVM, exceptions generate a set of functions of form __cxa_find_matching_catch_1(), __cxa_find_matching_catch_2(), etc.
	// where the number specifies the number of arguments. In Emscripten, route all these to a single function '__cxa_find_matching_catch'
	// that variadically processes all of these functions using JS 'arguments' object.
	if (item.identMangled.startsWith('___cxa_find_matching_catch_')) {
	if (DISABLE_EXCEPTION_THROWING) {
	error('DISABLE_EXCEPTION_THROWING was set (likely due to -fno-exceptions), which means no C++ exception throwing support code is linked in, but exception catching code appears. Either do not set DISABLE_EXCEPTION_THROWING (if you do want exception throwing) or compile all source files with -fno-except (so that no exceptions support code is required); also make sure DISABLE_EXCEPTION_CATCHING is set to the right value - if you want exceptions, it should be off, and vice versa.');
	return;
	}
	var num = +item.identMangled.split('_').slice(-1)[0];
	addCxaCatch(num);
	// Continue, with the code below emitting the proper JavaScript based on
	// what we just added to the library.
	}

	function addFromLibrary(item, dependent) {
	// dependencies can be JS functions, which we just run
	if (typeof item == 'function') return item();

	var ident = item.identOrig;
	var finalName = item.identMangled;

	if (ident in addedLibraryItems) return '';
	addedLibraryItems[ident] = true;

	// don't process any special identifiers. These are looked up when processing the base name of the identifier.
	if (isJsLibraryConfigIdentifier(ident)) {
	return '';
	}

	// if the function was implemented in compiled code, we just need to export it so we can reach it from JS
	if (finalName in IMPLEMENTED_FUNCTIONS) {
	EXPORTED_FUNCTIONS[finalName] = 1;
	// stop here: we don't need to add anything from our js libraries, not even deps, compiled code is on it
	return '';
	}

	// Don't replace implemented functions with library ones (which can happen when we add dependencies).
	// Note: We don't return the dependencies here. Be careful not to end up where this matters
	if (finalName in Functions.implementedFunctions) return '';

	var noExport = false;

	if (!LibraryManager.library.hasOwnProperty(ident)) {
	if (!(finalName in IMPLEMENTED_FUNCTIONS) && !LINKABLE) {
	var msg = 'undefined symbol: ' + ident;
	if (dependent) msg += ' (referenced by ' + dependent + ')';
	if (ERROR_ON_UNDEFINED_SYMBOLS) {
	error(msg);
	if (!LLD_REPORT_UNDEFINED) {
	warnOnce('Link with `-s LLD_REPORT_UNDEFINED` to get more information on undefined symbols');
	}
	warnOnce('To disable errors for undefined symbols use `-s ERROR_ON_UNDEFINED_SYMBOLS=0`')
	warnOnce(finalName + ' may need to be added to EXPORTED_FUNCTIONS if it arrives from a system library')
	} else if (VERBOSE \|\| WARN_ON_UNDEFINED_SYMBOLS) {
	warn(msg);
	}
	if (ident === 'main' && STANDALONE_WASM) {
	warn('To build in STANDALONE_WASM mode without a main(), use emcc --no-entry');
	}
	}
	if (!RELOCATABLE) {
	// emit a stub that will fail at runtime
	LibraryManager.library[ident] = new Function("err('missing function: " + ident + "'); abort(-1);");
	// We have already warned/errored about this function, so for the purposes of Closure use, mute all type checks
	// regarding this function, marking ot a variadic function that can take in anything and return anything.
	// (not useful to warn/error multiple times)
	LibraryManager.library[ident + '__docs'] = '/** @type {function(...):?} /';
	} else {
	var target = "Module['" + finalName + "']";
	var assertion = '';
	if (ASSERTIONS) {
	var what = 'function';
	assertion += 'if (!' + target + ') abort("external symbol \'' + ident + '\' is missing. perhaps a side module was not linked in? if this function was expected to arrive from a system library, try to build the MAIN_MODULE with EMCC_FORCE_STDLIBS=1 in the environment");\n';

	}
	var functionBody = assertion + "return " + target + ".apply(null, arguments);";
	LibraryManager.library[ident] = new Function(functionBody);
	noExport = true;
	}
	}

	var original = LibraryManager.library[ident];
	var snippet = original;
	var redirectedIdent = null;
	var deps = LibraryManager.library[ident + '__deps'] \|\| [];
	if (!Array.isArray(deps)) {
	error('JS library directive ' + ident + '__deps=' + deps.toString() + ' is of type ' + typeof deps + ', but it should be an array!');
	return;
	}
	deps.forEach((dep) => {
	if (typeof snippet === 'string' && !(dep in LibraryManager.library)) warn('missing library dependency ' + dep + ', make sure you are compiling with the right options (see #if in src/library*.js)');
	});
	var isFunction = false;

	if (typeof snippet === 'string') {
	if (snippet[0] != '=') {
	var target = LibraryManager.library[snippet];
	if (target) {
	// Redirection for aliases. We include the parent, and at runtime make ourselves equal to it.
	// This avoid having duplicate functions with identical content.
	redirectedIdent = snippet;
	deps.push(snippet);
	snippet = mangleCSymbolName(snippet);
	}
	// In asm, we need to know about library functions. If there is a target, though, then no
	// need to consider this a library function - we will call directly to it anyhow
	if (!redirectedIdent && (typeof target == 'function')) {
	Functions.libraryFunctions[finalName] = 1;
	}
	}
	} else if (typeof snippet === 'object') {
	snippet = stringifyWithFunctions(snippet);
	} else if (typeof snippet === 'function') {
	isFunction = true;
	snippet = processLibraryFunction(snippet, ident, finalName);
	if (!isJsOnlyIdentifier(ident[0])) {
	Functions.libraryFunctions[finalName] = 1;
	}
	}

	// If a JS library item specifies xxx_import: true, then explicitly mark that symbol to be exported
	// to wasm module.
	if (LibraryManager.library[ident + '__import']) {
	Functions.libraryFunctions[finalName] = 1;
	}

	if (ONLY_CALC_JS_SYMBOLS)
	return '';

	var postsetId = ident + '__postset';
	var postset = LibraryManager.library[postsetId];
	if (postset) {
	// A postset is either code to run right now, or some text we should emit.
	// If it's code, it may return some text to emit as well.
	if (typeof postset === 'function') {
	postset = postset();
	}
	if (postset && !addedLibraryItems[postsetId]) {
	addedLibraryItems[postsetId] = true;
	itemsDict.GlobalVariablePostSet.push({
	JS: postset + ';'
	});
	}
	}

	if (redirectedIdent) {
	deps = deps.concat(LibraryManager.library[redirectedIdent + '__deps'] \|\| []);
	}
	// In asm, dependencies implemented in C might be needed by JS library functions.
	// We don't know yet if they are implemented in C or not. To be safe, export such
	// special cases.
	[LIBRARY_DEPS_TO_AUTOEXPORT].forEach((special) => {
	deps.forEach((dep) => {
	if (dep == special && !EXPORTED_FUNCTIONS[dep]) {
	EXPORTED_FUNCTIONS[dep] = 1;
	}
	});
	});
	if (VERBOSE) {
	printErr('adding ' + finalName + ' and deps ' + deps + ' : ' + (snippet + '').substr(0, 40));
	}
	var identDependents = ident + "__deps: ['" + deps.join("','")+"']";
	function addDependency(dep) {
	if (typeof dep !== 'function') {
	dep = {identOrig: dep, identMangled: mangleCSymbolName(dep)};
	}
	return addFromLibrary(dep, identDependents + ', referenced by ' + dependent);
	}
	var depsText = (deps ? deps.map(addDependency).filter((x) => x != '').join('\n') + '\n' : '');
	var contentText;
	if (isFunction) {
	// Emit the body of a JS library function.
	var proxyingMode = LibraryManager.library[ident + '__proxy'];
	if (USE_PTHREADS && proxyingMode) {
	if (proxyingMode !== 'sync' && proxyingMode !== 'async') {
	throw 'Invalid proxyingMode ' + ident + '__proxy: \'' + proxyingMode + '\' specified!';
	}
	var sync = proxyingMode === 'sync';
	assert(typeof original === 'function');
	contentText = modifyFunction(snippet, (name, args, body) => {
	return 'function ' + name + '(' + args + ') {\n' +
	'if (ENVIRONMENT_IS_PTHREAD) return _emscripten_proxy_to_main_thread_js(' + proxiedFunctionTable.length + ', ' + (+sync) + (args ? ', ' : '') + args + ');\n' + body + '}\n';
	});
	proxiedFunctionTable.push(finalName);
	} else {
	contentText = snippet; // Regular JS function that will be executed in the context of the calling thread.
	}
	} else if (typeof snippet === 'string' && snippet.indexOf(';') == 0) {
	// In JS libraries
	// foo: ';[code here verbatim]'
	// emits
	// 'var foo;[code here verbatim];'
	contentText = 'var ' + finalName + snippet;
	if (snippet[snippet.length-1] != ';' && snippet[snippet.length-1] != '}') contentText += ';';
	} else {
	// In JS libraries
	// foo: '=[value]'
	// emits
	// 'var foo = [value];'
	if (typeof snippet === 'string' && snippet[0] == '=') snippet = snippet.substr(1);
	contentText = 'var ' + finalName + '=' + snippet + ';';
	}
	var sig = LibraryManager.library[ident + '__sig'];
	// asm module exports are done in emscripten.py, after the asm module is ready. Here
	// we also export library methods as necessary.
	if ((EXPORT_ALL \|\| (finalName in EXPORTED_FUNCTIONS)) && !noExport) {
	contentText += '\nModule["' + finalName + '"] = ' + finalName + ';';
	}
	if (MAIN_MODULE && sig) {
	contentText += '\n' + finalName + '.sig = \'' + sig + '\';';
	}

	var commentText = '';
	if (LibraryManager.library[ident + '__docs']) {
	commentText = LibraryManager.library[ident + '__docs'] + '\n';
	}

	return depsText + commentText + contentText;
	}

	itemsDict.functionStub.push(item);
	item.JS = addFromLibrary(item, 'top-level compiled C/C++ code');
	}

	// Final combiner

	function finalCombiner() {
	var splitPostSets = splitter(itemsDict.GlobalVariablePostSet, (x) => x.ident && x.dependencies);
	itemsDict.GlobalVariablePostSet = splitPostSets.leftIn;
	var orderedPostSets = splitPostSets.splitOut;

	var limit = orderedPostSets.length * orderedPostSets.length;
	for (var i = 0; i < orderedPostSets.length; i++) {
	for (var j = i+1; j < orderedPostSets.length; j++) {
	if (orderedPostSets[j].ident in orderedPostSets[i].dependencies) {
	var temp = orderedPostSets[i];
	orderedPostSets[i] = orderedPostSets[j];
	orderedPostSets[j] = temp;
	i--;
	limit--;
	assert(limit > 0, 'Could not sort postsets!');
	break;
	}
	}
	}

	itemsDict.GlobalVariablePostSet = itemsDict.GlobalVariablePostSet.concat(orderedPostSets);

	//

	if (!mainPass) {
	var generated = itemsDict.function.concat(itemsDict.type).concat(itemsDict.GlobalVariableStub).concat(itemsDict.GlobalVariable);
	print(generated.map((item) => item.JS).join('\n'));
	return;
	}

	var shellFile = SHELL_FILE ? SHELL_FILE : (MINIMAL_RUNTIME ? 'shell_minimal.js' : 'shell.js');

	var shellParts = read(shellFile).split('{{BODY}}');
	print(processMacros(preprocess(shellParts[0], shellFile)));
	var pre;
	if (MINIMAL_RUNTIME) {
	pre = processMacros(preprocess(read('preamble_minimal.js'), 'preamble_minimal.js'));
	} else {
	pre = processMacros(preprocess(read('support.js'), 'support.js')) +
	processMacros(preprocess(read('preamble.js'), 'preamble.js'));
	}
	print(pre);

	// Print out global variables and postsets TODO: batching
	var legalizedI64sDefault = legalizedI64s;
	legalizedI64s = false;

	var globalsData = {functionStubs: []}
	JSify(globalsData, true);
	globalsData = null;

	var generated = itemsDict.functionStub.concat(itemsDict.GlobalVariablePostSet);
	generated.forEach((item) => print(indentify(item.JS \|\| '', 2)));

	legalizedI64s = legalizedI64sDefault;

	if (USE_PTHREADS) {
	print('\n // proxiedFunctionTable specifies the list of functions that can be called either synchronously or asynchronously from other threads in postMessage()d or internally queued events. This way a pthread in a Worker can synchronously access e.g. the DOM on the main thread.')
	print('\nvar proxiedFunctionTable = [' + proxiedFunctionTable.join() + '];\n');
	}

	if (!MINIMAL_RUNTIME) {
	print('var ASSERTIONS = ' + !!ASSERTIONS + ';\n');

	print(preprocess(read('arrayUtils.js')));
	}

	if (SUPPORT_BASE64_EMBEDDING && !MINIMAL_RUNTIME) {
	print(preprocess(read('base64Utils.js')));
	}

	if (abortExecution) throw Error('Aborting compilation due to previous errors');

	// This is the main 'post' pass. Print out the generated code that we have here, together with the
	// rest of the output that we started to print out earlier (see comment on the
	// "Final shape that will be created").
	print('// EMSCRIPTEN_END_FUNCS\n');

	if (HEADLESS) {
	print('if (!ENVIRONMENT_IS_WEB) {');
	print(read('headlessCanvas.js'));
	print('\n');
	print(read('headless.js').replace("'%s'", "'http://emscripten.org'").replace("'?%s'", "''").replace("'?%s'", "'/'").replace('%s,', 'null,').replace('%d', '0'));
	print('}');
	}
	if (PROXY_TO_WORKER) {
	print('if (ENVIRONMENT_IS_WORKER) {\n');
	print(read('webGLWorker.js'));
	print(processMacros(preprocess(read('proxyWorker.js'), 'proxyWorker.js')));
	print('}');
	}
	if (DETERMINISTIC) {
	print(read('deterministic.js'));
	}

	var postFile = MINIMAL_RUNTIME ? 'postamble_minimal.js' : 'postamble.js';
	var post = processMacros(preprocess(read(postFile), postFile));
	print(post);

	var shellParts = read(shellFile).split('{{BODY}}');
	print(processMacros(preprocess(shellParts[1], shellFile)));

	PassManager.serialize();
	}

	// Data

	if (mainPass) {
	data.functionStubs.forEach(functionStubHandler);
	}

	finalCombiner();
	}