pythonGH-115978: Disable *readv() and *writev() on WASI

Wasmtime doesn't implement them in a way to pass test_posix (bytecodealliance/wasmtime#7830).

This fix allows running under WASI 0.2 primitives for wasmtime.

.devcontainer/Dockerfile

@@ -6,7 +6,7 @@ ENV WASI_SDK_VERSION=20
 ENV WASI_SDK_PATH=/opt/wasi-sdk
 
 ENV WASMTIME_HOME=/opt/wasmtime
-ENV WASMTIME_VERSION=14.0.4
+ENV WASMTIME_VERSION=18.0.2
 ENV WASMTIME_CPU_ARCH=x86_64
 
 RUN dnf -y --nodocs --setopt=install_weak_deps=False install /usr/bin/{blurb,clang,curl,git,ln,tar,xz} 'dnf-command(builddep)' && \

Misc/NEWS.d/next/Library/2024-03-01-14-22-08.gh-issue-115978.r2ePTo.rst

@@ -0,0 +1,4 @@
+Disable preadv(), readv(), pwritev(), and writev() on WASI.
+
+Under wasmtime for WASI 0.2, these functions don't pass test_posix
+(https://github.com/bytecodealliance/wasmtime/issues/7830).

Tools/wasm/config.site-wasm32-wasi

@@ -40,3 +40,12 @@ ac_cv_header_netpacket_packet_h=no
 
 # Disable int-conversion for wask-sdk as it triggers an error from version 17.
 ac_cv_disable_int_conversion=yes
+
+# preadv(), readv(), pwritev(), and writev() under wasmtime's WASI 0.2 support
+# do not use more than the first buffer provided, failing under test_posix.
+# Since wasmtime will not be changing this behaviour, disable the functions.
+# https://github.com/bytecodealliance/wasmtime/issues/7830
+ac_cv_func_preadv=no
+ac_cv_func_readv=no
+ac_cv_func_pwritev=no
+ac_cv_func_writev=no

Tools/wasm/wasi.py

@@ -277,18 +277,23 @@ def clean_contents(context):
 
 
 def main():
-    default_host_runner = (f"{shutil.which('wasmtime')} run "
-                        # Make sure the stack size will work for a pydebug
-                        # build.
-                        # The 8388608 value comes from `ulimit -s` under Linux
-                        # which equates to 8291 KiB.
-                        "--wasm max-wasm-stack=8388608 "
-                        # Enable thread support.
-                        "--wasm threads=y --wasi threads=y "
-                        # Map the checkout to / to load the stdlib from /Lib.
-                        "--dir {HOST_DIR}::{GUEST_DIR} "
-                        # Set PYTHONPATH to the sysconfig data.
-                        "--env {ENV_VAR_NAME}={ENV_VAR_VALUE}")
+    host_runner_parts = [
+        f"{shutil.which('wasmtime')} run",
+        # Make sure the stack size will work for a pydebug
+        # build.
+        # The 8388608 value comes from `ulimit -s` under Linux
+        # which equates to 8291 KiB.
+        "--wasm max-wasm-stack=8388608",
+        # Enable thread support.
+        #"--wasm threads=y --wasi threads=y "
+        # Use WASI 0.2 primitives
+        "--wasi preview2",
+        # Map the checkout to / to load the stdlib from /Lib.
+        "--dir {HOST_DIR}::{GUEST_DIR}",
+        # Set PYTHONPATH to the sysconfig data.
+        "--env {ENV_VAR_NAME}={ENV_VAR_VALUE}"
+    ]
+    default_host_runner = " ".join(host_runner_parts)
 
     parser = argparse.ArgumentParser()
     subcommands = parser.add_subparsers(dest="subcommand")