[3.11] GH-115978: Disable *readv() and *writev() on WASI (GH-116228…

…) (GH-116232)

GH-115978: Disable `*readv()` and `*writev()` on WASI (GH-116228)

Wasmtime doesn't implement these functions in a way to pass test_posix (bytecodealliance/wasmtime#7830).
(cherry picked from commit 5dc8c84)

Co-authored-by: Brett Cannon <brett@python.org>

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

@@ -43,3 +43,12 @@ 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