Revert default for GROWABLE_ARRAYBUFFERS to 0

ChangeLog.md

@@ -38,6 +38,8 @@ See docs/process.md for more on how version tagging works.
 - `-fcoverage-mapping` is currently broken due to a mismatch between the version
   of LLVM used and the imported version of compiler-rt.  We hope to fix this
   in the next release. (#27261)
+- The default value for `GROWABLE_ARRAYBUFFERS` was reverted to `0` since we
+  found issues with Web API compatibility. (#27260)
 
 6.0.2 - 07/01/26
 ----------------

site/source/docs/tools_reference/settings_reference.rst

@@ -3435,13 +3435,13 @@ GROWABLE_ARRAYBUFFERS
 Enable support for growable views of Wasm memory. This is a recent Web
 platform feature that can make growing the Wasm memory more efficient,
 especially in multi-threaded builds.
-The default setting of 1 will auto-detect the presence of this API and use
+Setting this to 1 will auto-detect the presence of this API and use
 it when available.
 Setting this to 2 will unconditionally require it. This is the only way
 to completely remove the overhead of growable memory + pthreads.
 This settings does nothing unless ALLOW_MEMORY_GROWTH is set.
 
-Default value: 1
+Default value: 0
 
 .. _cross_origin:
 

src/settings.js

@@ -2276,13 +2276,13 @@ var JS_BASE64_API = false;
 // Enable support for growable views of Wasm memory. This is a recent Web
 // platform feature that can make growing the Wasm memory more efficient,
 // especially in multi-threaded builds.
-// The default setting of 1 will auto-detect the presence of this API and use
+// Setting this to 1 will auto-detect the presence of this API and use
 // it when available.
 // Setting this to 2 will unconditionally require it. This is the only way
 // to completely remove the overhead of growable memory + pthreads.
 // This settings does nothing unless ALLOW_MEMORY_GROWTH is set.
 // [link]
-var GROWABLE_ARRAYBUFFERS = 1;
+var GROWABLE_ARRAYBUFFERS = 0;
 
 // If the emscripten-generated program is hosted on separate origin then
 // starting new pthread worker can violate CSP rules.  Enabling

test/codesize/test_codesize_mem_O3_grow.json

@@ -1,10 +1,10 @@
 {
-  "a.out.js": 4394,
-  "a.out.js.gz": 2155,
+  "a.out.js": 4347,
+  "a.out.js.gz": 2138,
   "a.out.nodebug.wasm": 5261,
   "a.out.nodebug.wasm.gz": 2419,
-  "total": 9655,
-  "total_gz": 4574,
+  "total": 9608,
+  "total_gz": 4557,
   "sent": [
     "a (emscripten_resize_heap)"
   ],

test/codesize/test_codesize_mem_O3_grow_standalone.json

@@ -1,10 +1,10 @@
 {
-  "a.out.js": 3860,
-  "a.out.js.gz": 1896,
+  "a.out.js": 3813,
+  "a.out.js.gz": 1874,
   "a.out.nodebug.wasm": 5641,
   "a.out.nodebug.wasm.gz": 2659,
-  "total": 9501,
-  "total_gz": 4555,
+  "total": 9454,
+  "total_gz": 4533,
   "sent": [
     "args_get",
     "args_sizes_get",

test/codesize/test_codesize_minimal_pthreads_memgrowth.json

@@ -1,10 +1,10 @@
 {
-  "a.out.js": 7550,
-  "a.out.js.gz": 3708,
+  "a.out.js": 7379,
+  "a.out.js.gz": 3639,
   "a.out.nodebug.wasm": 19064,
   "a.out.nodebug.wasm.gz": 8804,
-  "total": 26614,
-  "total_gz": 12512,
+  "total": 26443,
+  "total_gz": 12443,
   "sent": [
     "a (memory)",
     "b (exit)",