fix: run correctly on modern Emscripten + release-grade performance flags (~15x less CPU)

configure.ac

@@ -26,7 +26,13 @@ OPT_LEVEL=3
 if test "$GCC" = "yes"
 then
         WARNINGS="-Wall -Wdeclaration-after-statement -Wredundant-decls"
-        CFLAGS="-O$OPT_LEVEL -g $WARNINGS $orig_CFLAGS"
+        # -std=gnu99: modern clang defaults to C23, where true/false are
+        # keywords and collide with the boolean enum in doomtype.h.
+        # -fno-strict-aliasing: the id-era code type-puns byte buffers through
+        # int16/int32 pointers everywhere (e.g. wipe_shittyColMajorXform); at
+        # -O3 modern LLVM exploits that UB and miscompiles the screen-wipe
+        # into a transposed, never-finishing mess.
+        CFLAGS="-O$OPT_LEVEL -std=gnu99 -fno-strict-aliasing $WARNINGS $orig_CFLAGS"
 fi
 
 # PKG_CHECK_MODULES(SDL, [sdl2 >= 2.0.7])
@@ -115,10 +121,19 @@ AS_IF([test "x$with_libpng" != xno], [
 
 # TODO: We currently link everything against libraries that don't need it.
 # Use the specific library CFLAGS/LIBS variables instead of setting them here.
-EMFLAGS="-gsource-map -s INVOKE_RUN=1 -s USE_SDL=2 -s USE_SDL_MIXER=2 -s LEGACY_GL_EMULATION=0 -s USE_SDL_NET=2 -s ASSERTIONS=0 -s WASM=1 -s ALLOW_MEMORY_GROWTH=0 -s FORCE_FILESYSTEM=1 -s EXTRA_EXPORTED_RUNTIME_METHODS=[['FS','ccall']] -s SAFE_HEAP=1 -s EXIT_RUNTIME=1 -s STACK_OVERFLOW_CHECK=1 -s PROXY_POSIX_SOCKETS=0 -s USE_PTHREADS=0 -s PROXY_TO_PTHREAD=0 -s TOTAL_MEMORY=64MB -s ERROR_ON_UNDEFINED_SYMBOLS=0 -s ASYNCIFY -O3 --source-map-base /"
+# Release flags: no SAFE_HEAP/STACK_OVERFLOW_CHECK/source maps (debug-only, large
+# runtime cost), closure for smaller JS glue. ASYNCIFY is still required for
+# emscripten_sleep() on startup and netgame wait paths (see I_Sleep).
+# Do NOT add -flto: cross-TU LTO at -O3 turns undefined behavior in this
+# 1993-era codebase into a compile-time `unreachable` trap in main() (verified:
+# the LTO build crashes immediately after Z_Init).
+# STACK_SIZE=5MB restores the pre-3.1.25 Emscripten default; the modern 64KB
+# default is too small for Doom's init path.
+EMFLAGS="-s INVOKE_RUN=1 -s USE_SDL=2 -s USE_SDL_MIXER=2 -s LEGACY_GL_EMULATION=0 -s USE_SDL_NET=2 -s ASSERTIONS=0 -s WASM=1 -s ALLOW_MEMORY_GROWTH=0 -s FORCE_FILESYSTEM=1 -s EXPORTED_RUNTIME_METHODS=[['FS','ccall']] -s EXIT_RUNTIME=1 -s PROXY_POSIX_SOCKETS=0 -s USE_PTHREADS=0 -s PROXY_TO_PTHREAD=0 -s INITIAL_MEMORY=64MB -s STACK_SIZE=5MB -s ERROR_ON_UNDEFINED_SYMBOLS=0 -s ASYNCIFY -O3"
+EMLDFLAGS="--closure 1"
 
 CFLAGS="$CFLAGS $SDL_CFLAGS ${SAMPLERATE_CFLAGS:-} ${PNG_CFLAGS:-} $EMFLAGS"
-LDFLAGS="$LDFLAGS $SDL_LIBS ${SAMPLERATE_LIBS:-} ${PNG_LIBS:-} $EMFLAGS -lwebsocket.js"
+LDFLAGS="$LDFLAGS $SDL_LIBS ${SAMPLERATE_LIBS:-} ${PNG_LIBS:-} $EMFLAGS $EMLDFLAGS -lwebsocket.js"
 
 AC_CHECK_LIB(m, log)
 

src/d_loop.c

@@ -661,16 +661,15 @@ void TryRunTics(void)
 
         if (lowtic < gametic / ticdup) I_Error("TryRunTics: lowtic < gametic");
 
-        // Still no tics to run? Sleep until some are available.
+        // Still no tics to run? Return to the browser event loop instead
+        // of sleeping: I_Sleep() is emscripten_sleep(), which Asyncify
+        // implements by unwinding and rewinding the entire call stack.
+        // This loop is reached on almost every frame (the 60Hz+ rAF main
+        // loop outpaces the 35Hz tic rate), so sleeping here put that
+        // unwind cost on the hot path. The main loop calls TryRunTics()
+        // again on the next frame, which serves the same purpose.
         if (lowtic < gametic / ticdup + counts) {
-            // If we're in a netgame, we might spin forever waiting for
-            // new network data to be received. So don't stay in here
-            // forever - give the menu a chance to work.
-            if (I_GetTime() / ticdup - entertic >= MAX_NETGAME_STALL_TICS) {
-                return;
-            }
-
-            I_Sleep(1);
+            return;
         }
     }
 

src/doom/d_main.c

@@ -375,11 +375,14 @@ void D_RunFrame()
     static boolean wipe;
 
     if (wipe) {
-        do {
-            nowtime = I_GetTime();
-            tics = nowtime - wipestart;
-            I_Sleep(1);
-        } while (tics <= 0);
+        // No game tic has elapsed yet: return to the browser event loop
+        // rather than Asyncify-sleeping (stack unwind/rewind) inside the
+        // frame. The main loop re-enters D_RunFrame on the next rAF frame.
+        nowtime = I_GetTime();
+        tics = nowtime - wipestart;
+        if (tics <= 0) {
+            return;
+        }
 
         wipestart = nowtime;
         wipe = !wipe_ScreenWipe(wipe_Melt, 0, 0, SCREENWIDTH, SCREENHEIGHT, tics);

src/doom/r_defs.h

@@ -392,7 +392,10 @@ typedef struct
     // If false use 0 for any position.
     // Note: as eight entries are available,
     //  we might as well insert the same name eight times.
-    boolean	rotate;
+    // int, not boolean: R_InstallSpriteLump memsets this to -1 as an
+    // "uninitialized" marker and compares against it; a 1-byte bool
+    // cannot hold -1.
+    int		rotate;
 
     // Lump to use for view angles 0-7.
     short	lump[8];

src/doomtype.h

@@ -100,22 +100,15 @@
 
 #include <inttypes.h>
 
-#if defined(__cplusplus) || defined(__bool_true_false_are_defined)
-
-// Use builtin bool type with C++.
+// boolean must be the same size in every translation unit. The old
+// conditional (enum when <stdbool.h> hadn't been included yet, bool when it
+// had) made boolean 4 bytes in some TUs and 1 byte in others, so 4-byte
+// stores to shared globals like netgame clobbered adjacent globals
+// (caught by ASan as a global-buffer-overflow). Always use bool.
+#include <stdbool.h>
 
 typedef bool boolean;
 
-#else
-
-typedef enum 
-{
-    false, 
-    true
-} boolean;
-
-#endif
-
 typedef uint8_t byte;
 typedef uint8_t pixel_t;
 typedef int16_t dpixel_t;

src/index.html

@@ -56,14 +56,25 @@
         <script>
             var commonArgs = ["-iwad", "doom1.wad", "-window", "-nogui", "-nomusic", "-config", "default.cfg", "-servername", "doomflare"];
 
+            // Surface wasm crash stacks in the console; "Uncaught (in promise)"
+            // errors from the async runtime are otherwise swallowed with no trace.
+            window.addEventListener("unhandledrejection", (e) => {
+                console.error("UNHANDLED: " + (e.reason && (e.reason.stack || e.reason)));
+            });
+            window.addEventListener("error", (e) => {
+                console.error("ERROR: " + (e.error && e.error.stack ? e.error.stack : e.message));
+            });
+
             var Module = {
-                onRuntimeInitialized: () => {
-                    callMain(commonArgs);
-                },
-                noInitialRun: true,
+                // main() runs automatically (INVOKE_RUN) once the preloaded
+                // files below are ready; callMain is no longer exported by
+                // recent Emscripten versions.
+                arguments: commonArgs,
                 preRun: () => {
-                    Module.FS.createPreloadedFile("", "doom1.wad", "doom1.wad", true, true);
-                    Module.FS.createPreloadedFile("", "default.cfg", "default.cfg", true, true);
+                    // Emscripten 6.x renamed FS.createPreloadedFile to
+                    // FS.preloadFile, exported on Module as FS_preloadFile.
+                    Module.FS_preloadFile("", "doom1.wad", "doom1.wad", true, true);
+                    Module.FS_preloadFile("", "default.cfg", "default.cfg", true, true);
                 },
                 printErr: function (text) {
                     if (arguments.length > 1) text = Array.prototype.slice.call(arguments).join(" ");