Set what were default values for Web platform linker flags -sSTACK_SIZE and -sDEFAULT_PTHREAD_STACK_SIZE

[adamscott]

Emscripten did some changes regarding some linkerflags.

• they updated -sSTACK_SIZE from 5MB to 64KB and -sDEFAULT_PTHREAD_STACK_SIZE from 2MB to 64KB on 3.1.27.
• they updated -sDEFAULT_PTHREAD_STACK_SIZE to match -sSTACK_SIZE on 3.1.30.

This PR sets back both linkerflags to their original value for now on.

Fixes #85564

[YuriSizov]

So from what I can tell, where we break is here:

extern zipFile ZEXPORT zipOpen2(const char *pathname, int append, zipcharpc* globalcomment, zlib_filefunc_def* pzlib_filefunc32_def) {
    if (pzlib_filefunc32_def != NULL)
    {
        zlib_filefunc64_32_def zlib_filefunc64_32_def_fill;
        fill_zlib_filefunc64_32_def_from_filefunc32(&zlib_filefunc64_32_def_fill,pzlib_filefunc32_def);
        return zipOpen3(pathname, append, globalcomment, &zlib_filefunc64_32_def_fill); // <-- here
    }
    else
        return zipOpen3(pathname, append, globalcomment, NULL);
}

Without these changes the values on stack in WASM when this call happens are

$var0: i32 {value: 24090136}
$var1: i32 {value: 0}
$var2: i32 {value: 0}
$var3: i32 {value: 63768}
$var4: i32 {value: 63696}

And with these changes its like this

$var0: i32 {value: 49976928}
$var1: i32 {value: 0}
$var2: i32 {value: 0}
$var3: i32 {value: 5241112}
$var4: i32 {value: 5241040}

So it seems we're allocating exactly what the amount of STACK_SIZE specified for these last two variables. One of which seems to be the zlib_filefunc64_32_def struct, which is a collection of function pointers. Seems like 64 kb just doesn't fit this amount of pointers. But I guess 5 mb may be a bit too much and we can tweak and reduce the number if needed.

All that said, this fixes the issue in my testing.

[akien-mga]

The fix is good, but the problem is that it's going to break compiling with Emscripten < 3.1.30, since it doesn't know those linker options. I tried with 3.1.18:

em++: error: Attempt to set a non-existent setting: 'STACK_SIZE'
 - did you mean one of ASYNCIFY_STACK_SIZE?
 - perhaps a typo in emcc's  -sX=Y  notation?
 - (see src/settings.js for valid values)

We should add the options conditionally based on the Emscripten version.

[akien-mga]

Fix:

diff --git a/platform/web/detect.py b/platform/web/detect.py
index ddfd3515f9..c2c1b28766 100644
--- a/platform/web/detect.py
+++ b/platform/web/detect.py
@@ -186,10 +186,15 @@ def configure(env: "Environment"):
     env["LIBPREFIXES"] = ["$LIBPREFIX"]
     env["LIBSUFFIXES"] = ["$LIBSUFFIX"]
 
+    # Get version info for checks below.
+    cc_version = get_compiler_version(env)
+    cc_semver = (cc_version["major"], cc_version["minor"], cc_version["patch"])
+
     env.Prepend(CPPPATH=["#platform/web"])
     env.Append(CPPDEFINES=["WEB_ENABLED", "UNIX_ENABLED"])
 
-    env.Append(LINKFLAGS=["-s", "STACK_SIZE=5MB"])
+    if cc_semver >= (3, 1, 27):
+        env.Append(LINKFLAGS=["-s", "STACK_SIZE=5MB"])
 
     if env["opengl3"]:
         env.AppendUnique(CPPDEFINES=["GLES3_ENABLED"])
@@ -205,14 +210,11 @@ def configure(env: "Environment"):
     env.Append(CPPDEFINES=["PTHREAD_NO_RENAME"])
     env.Append(CCFLAGS=["-s", "USE_PTHREADS=1"])
     env.Append(LINKFLAGS=["-s", "USE_PTHREADS=1"])
-    env.Append(LINKFLAGS=["-s", "DEFAULT_PTHREAD_STACK_SIZE=2MB"])
+    if cc_semver >= (3, 1, 30):
+        env.Append(LINKFLAGS=["-s", "DEFAULT_PTHREAD_STACK_SIZE=2MB"])
     env.Append(LINKFLAGS=["-s", "PTHREAD_POOL_SIZE=8"])
     env.Append(LINKFLAGS=["-s", "WASM_MEM_MAX=2048MB"])
 
-    # Get version info for checks below.
-    cc_version = get_compiler_version(env)
-    cc_semver = (cc_version["major"], cc_version["minor"], cc_version["patch"])
-
     if env["lto"] != "none":
         # Workaround https://github.com/emscripten-core/emscripten/issues/19781.
         if cc_semver >= (3, 1, 42) and cc_semver < (3, 1, 46):

[YuriSizov]

Prior to 3.1.25 it was called TOTAL_STACK, so we can probably always set it with this caveat.

[akien-mga]

Updated with my diff + @YuriSizov's suggestion.

[akien-mga]

Actually this may not need to be version specific, they just changed the default in 3.1.30 but the flag existed before, so we can always set it.

[akien-mga]

Thanks!

[akien-mga]

Cherry-picked for 4.2.1.

[akien-mga]

Cherry-picked for 4.1.4.

[akien-mga]

Cherry-picked for 3.6.

[akien-mga]

Cherry-picked for 3.5.4.