Fix WASM memory allocation failure (#4989) (#7887)

* Fix WASM memory allocation failure (#4989)

This commit addresses the unbounded memory allocation issue on WASM targets that caused minimal programs (like  = 1) to fail with ~79MB allocation errors in constrained runtimes like wasmi.

The fixes include:
1. Capping the max memory limit at 64MB and restricting stack size to 1MB via linker flags in .cargo/config.toml.
2. Reducing the minimum chunk size of the DataStack from 16KB to 4KB on WASM targets to shrink the initial memory footprint.
3. Adding a wasm-release profile in the root Cargo.toml optimized for size with opt-level = s, LTO enabled, and symbols stripped.

* Trigger CI rerun

* Address review feedback: add comments, use cfg! for MIN_CHUNK_SIZE

* Remove duplicate MIN_CHUNK_SIZE definition

* Fix duplicate MIN_CHUNK_SIZE and format for prek lint

* Update CI to use wasm-release profile for WASM tests

* Remove leftover conflict markers

* Clean remaining conflict markers in CI workflow

* Clean remaining conflict markers in CI workflow

* Trigger CI to pick up new required check

* Remove --max-memory flag, keep stack limit only

.cargo/config.toml

@@ -6,3 +6,16 @@ rustflags = "-C link-args=-Wl,--stack,8000000"
 
 [target.wasm32-unknown-unknown]
 rustflags = ["--cfg=getrandom_backend=\"wasm_js\""]
+
+# Enforce a 1 MB stack limit for WASI targets.
+# (Runaway heap growth is fixed by the smaller DataStack chunk
+# and the size‑optimized wasm‑release profile.)
+[target.wasm32-wasip1]
+rustflags = [
+    "-C", "link-arg=-zstack-size=1048576",
+]
+
+[target.wasm32-wasip2]
+rustflags = [
+    "-C", "link-arg=-zstack-size=1048576",
+]

.github/workflows/ci.yaml

@@ -779,11 +779,11 @@ jobs:
           clang: true
 
       - name: build rustpython
-        run: cargo build --release --target wasm32-wasip1 --no-default-features --features freeze-stdlib,stdlib,stdio,importlib,host_env --verbose
+        run: cargo build --profile wasm-release --target wasm32-wasip1 --no-default-features --features freeze-stdlib,stdlib,stdio,importlib,host_env --verbose
       - name: run snippets
-        run: wasmer run --dir "$(pwd)" target/wasm32-wasip1/release/rustpython.wasm -- "$(pwd)/extra_tests/snippets/stdlib_random.py"
+        run: wasmer run --dir "$(pwd)" target/wasm32-wasip1/wasm-release/rustpython.wasm -- "$(pwd)/extra_tests/snippets/stdlib_random.py"
       - name: run cpython unittest
-        run: wasmer run --dir "$(pwd)" target/wasm32-wasip1/release/rustpython.wasm -- "$(pwd)/Lib/test/test_int.py"
+        run: wasmer run --dir "$(pwd)" target/wasm32-wasip1/wasm-release/rustpython.wasm -- "$(pwd)/Lib/test/test_int.py"
 
   cargo_doc:
     needs:
@@ -820,3 +820,4 @@ jobs:
 
       - name: cargo doc
         run: cargo doc --locked
+

Cargo.toml

@@ -117,6 +117,14 @@ opt-level = 3
 [profile.release]
 lto = "thin"
 
+[profile.wasm-release]
+inherits = "release"
+opt-level = "s"
+lto = true
+codegen-units = 1
+strip = true
+panic = "abort"
+
 [patch.crates-io]
 parking_lot_core = { git = "https://github.com/youknowone/parking_lot", branch = "rustpython" }
 # REDOX START, Uncomment when you want to compile/check with redoxer

crates/vm/src/datastack.rs

@@ -9,7 +9,12 @@ use core::alloc::Layout;
 use core::ptr;
 
 /// Minimum chunk size in bytes (`_PY_DATA_STACK_CHUNK_SIZE`).
-const MIN_CHUNK_SIZE: usize = 16 * 1024;
+/// Smaller on WASM (4 KB) to reduce initial memory footprint; 16 KB otherwise.
+const MIN_CHUNK_SIZE: usize = if cfg!(target_arch = "wasm32") {
+    4 * 1024
+} else {
+    16 * 1024
+};
 
 /// Extra headroom (in bytes) to avoid allocating a new chunk for the next
 /// frame right after growing.