fix(mobile): _pyrepl pruning + mimalloc seccomp open() on 3.13/3.14 (#29)

Two distinct on-device runtime bugs that only surface on a genuine 3.13/3.14
mobile run (3.12 unaffected), found via mobile-forge genuine multi-Python mobile
tests (fork run 27439192170):

1. _pyrepl was pruned from the iOS + Android stdlib excludes as a "dev-only /
   interactive-REPL" module. But CPython 3.14 pdb.py imports _pyrepl at module
   load, so any on-device code importing pdb (incl. pytest) dies with
   "ModuleNotFoundError: No module named _pyrepl". 3.13 pdb does not import it,
   which is why 3.13 iOS was unaffected. Un-prune _pyrepl in
   darwin/python-darwin-stdlib.exclude + android/python-android-dart.exclude.

2. mimalloc (bundled in CPython since 3.13) issues a bare open(2) syscall from
   its load-time constructor (mi_process_load -> unix_detect_overcommit reading
   /proc/sys/vm/overcommit_memory) where SYS_open is defined (x86_64). Android
   bionic seccomp forbids open(2) -> SIGSYS at dlopen of libpython, before the
   interpreter starts. arm64 is unaffected (no SYS_open; mimalloc falls back to
   libc open() -> openat). Patch mi_prim_open to use SYS_openat
   (android/patches/mimalloc_seccomp_openat.patch, gated >=3.13 in build.sh).

Author: ndonkoHenri

android/build.sh

@@ -57,6 +57,12 @@ if [ $version_int -eq 312 ]; then
     # Android tooling; this 3.12-only patch matches that behavior at link time.
     patches+=" soname_linktime bldlibrary grp"
 fi
+if [ $version_int -ge 313 ]; then
+    # mimalloc (bundled since 3.13) issues a bare SYS_open at load on x86_64,
+    # which Android seccomp kills (SIGSYS) at dlopen of libpython. Switch it to
+    # SYS_openat. See patches/mimalloc_seccomp_openat.patch.
+    patches+=" mimalloc_seccomp_openat"
+fi
 for name in $patches; do
     patch_file="$script_dir/patches/$name.patch"
     echo "$patch_file"

android/patches/mimalloc_seccomp_openat.patch

@@ -0,0 +1,22 @@
+mimalloc: use SYS_openat instead of SYS_open (Android seccomp).
+
+CPython bundles mimalloc since 3.13. On Android, mimalloc's load-time constructor
+(mi_process_load -> unix_detect_overcommit, Objects/mimalloc/init.c) reads
+/proc/sys/vm/overcommit_memory through mi_prim_open. On platforms where SYS_open
+is defined (x86_64) mi_prim_open issues the bare open(2) syscall directly (to
+avoid recursion while mimalloc is still initializing). Android's bionic seccomp
+policy forbids open(2) -- only openat(2) is permitted -- so the kernel raises
+SIGSYS (SYS_SECCOMP) and the process is killed at dlopen() of libpython, before
+the interpreter starts. 3.12 has no mimalloc; arm64 is unaffected (it has no
+SYS_open, so mimalloc falls back to libc open(), which bionic routes through
+openat). SYS_openat(AT_FDCWD, ...) is semantically identical and allowed.
+
+--- a/Objects/mimalloc/prim/unix/prim.c
++++ b/Objects/mimalloc/prim/unix/prim.c
+@@ -67,5 +67,5 @@
+ static int mi_prim_open(const char* fpath, int open_flags) {
+-  return syscall(SYS_open,fpath,open_flags,0);
++  return syscall(SYS_openat,AT_FDCWD,fpath,open_flags,0);
+ }
+ static ssize_t mi_prim_read(int fd, void* buf, size_t bufsize) {
+   return syscall(SYS_read,fd,buf,bufsize);

android/python-android-dart.exclude

@@ -20,8 +20,8 @@ lib/python*/tkinter
 lib/python*/turtle*
 lib/python*/wsgiref
 # Interactive-REPL / dev-only modules + easter eggs / frozen demos (never imported when
-# running a script in embedded mode).
-lib/python*/_pyrepl
+# running a script in embedded mode). _pyrepl is intentionally NOT pruned: CPython 3.14's
+# pdb imports it at module load, so dropping it breaks pdb / pytest / anything that imports it.
 lib/python*/rlcompleter*
 lib/python*/tabnanny*
 lib/python*/antigravity*

darwin/python-darwin-stdlib.exclude

@@ -19,8 +19,9 @@ tkinter
 turtle*
 wsgiref
 # Interactive-REPL / dev-only modules — never imported when running a script (embedded
-# mode); plus easter eggs and frozen demo modules.
-_pyrepl
+# mode); plus easter eggs and frozen demo modules. _pyrepl is intentionally NOT pruned:
+# CPython 3.14's pdb imports it at module load, so dropping it breaks pdb / pytest /
+# anything that imports it on-device.
 rlcompleter*
 tabnanny*
 antigravity*