-O1

wasm@deco:~/trydynlib$ make -B
emcc -s WASM=0 -O1 -s SIDE_MODULE=1 -DLIBK_COMPILE -o libk_so.js libk.c
emcc -s WASM=0 -O1 -s MAIN_MODULE=1 -s RUNTIME_LINKED_LIBS="['libk_so.js']" -o prog.js prog.c

wasm@deco:~/trydynlib$ node prog.js
prog!
libk.kfunc1 -> 12

Makefile

@@ -10,6 +10,7 @@ SO	:= js
 endif
 
 #CC	+= -v
+CC	+= -O1
 
 all	: prog.js
 

libk_so.js

@@ -54,7 +54,7 @@ for (var i = gb; i < gb + 0; ++i) HEAP8[i] = 0;
 /* no memory initializer */
 // {{PRE_LIBRARY}}
 
-var ASSERTIONS = true;
+var ASSERTIONS = false;
 
 // Copyright 2017 The Emscripten Authors.  All rights reserved.
 // Emscripten is available under two separate licenses, the MIT license and the
@@ -91,10 +91,10 @@ function intArrayToString(array) {
 
 Module.asmGlobalArg = { "Math": Math, "Int8Array": Int8Array, "Int16Array": Int16Array, "Int32Array": Int32Array, "Uint8Array": Uint8Array, "Uint16Array": Uint16Array, "Uint32Array": Uint32Array, "Float32Array": Float32Array, "Float64Array": Float64Array, "NaN": NaN, "Infinity": Infinity };
 
-Module.asmLibraryArg = { "abort": abort, "assert": assert, "enlargeMemory": enlargeMemory, "getTotalMemory": getTotalMemory, "abortOnCannotGrowMemory": abortOnCannotGrowMemory, "abortStackOverflow": abortStackOverflow, "setTempRet0": setTempRet0, "getTempRet0": getTempRet0, "DYNAMICTOP_PTR": DYNAMICTOP_PTR, "tempDoublePtr": tempDoublePtr, "STACKTOP": STACKTOP, "STACK_MAX": STACK_MAX, "gb": gb, "fb": fb };
+Module.asmLibraryArg = { "abort": abort, "assert": assert, "enlargeMemory": enlargeMemory, "getTotalMemory": getTotalMemory, "abortOnCannotGrowMemory": abortOnCannotGrowMemory, "setTempRet0": setTempRet0, "getTempRet0": getTempRet0, "DYNAMICTOP_PTR": DYNAMICTOP_PTR, "tempDoublePtr": tempDoublePtr, "STACKTOP": STACKTOP, "STACK_MAX": STACK_MAX, "gb": gb, "fb": fb };
 // EMSCRIPTEN_START_ASM
 var asm = (/** @suppress {uselessCode} */ function(global, env, buffer) {
-'almost asm';
+'use asm';
 
 
   var HEAP8 = new global.Int8Array(buffer);
@@ -143,7 +143,6 @@ var asm = (/** @suppress {uselessCode} */ function(global, env, buffer) {
   var enlargeMemory=env.enlargeMemory;
   var getTotalMemory=env.getTotalMemory;
   var abortOnCannotGrowMemory=env.abortOnCannotGrowMemory;
-  var abortStackOverflow=env.abortStackOverflow;
   var setTempRet0=env.setTempRet0;
   var getTempRet0=env.getTempRet0;
   var tempFloat = 0.0;
@@ -156,8 +155,7 @@ function stackAlloc(size) {
   ret = STACKTOP;
   STACKTOP = (STACKTOP + size)|0;
   STACKTOP = (STACKTOP + 15)&-16;
-    if ((STACKTOP|0) >= (STACK_MAX|0)) abortStackOverflow(size|0);
-
+  
   return ret|0;
 }
 function stackSave() {
@@ -202,17 +200,6 @@ function runPostSets() {
 // EMSCRIPTEN_END_ASM
 (Module.asmGlobalArg, Module.asmLibraryArg, buffer);
 
-var real__kfunc1 = asm["_kfunc1"]; asm["_kfunc1"] = function() {
-  assert(runtimeInitialized, 'you need to wait for the runtime to be ready (e.g. wait for main() to be called)');
-  assert(!runtimeExited, 'the runtime was exited (use NO_EXIT_RUNTIME to keep it alive after main() exits)');
-  return real__kfunc1.apply(null, arguments);
-};
-
-var real_setThrew = asm["setThrew"]; asm["setThrew"] = function() {
-  assert(runtimeInitialized, 'you need to wait for the runtime to be ready (e.g. wait for main() to be called)');
-  assert(!runtimeExited, 'the runtime was exited (use NO_EXIT_RUNTIME to keep it alive after main() exits)');
-  return real_setThrew.apply(null, arguments);
-};
 var _kfunc1 = Module["_kfunc1"] = asm["_kfunc1"];
 var runPostSets = Module["runPostSets"] = asm["runPostSets"];
 var setThrew = Module["setThrew"] = asm["setThrew"];