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py/builtinimport: Remove weak links.

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In order to keep "import umodule" working, the existing mechanism is
replaced with a simple fallback to drop the "u".

This makes importing of built-ins no longer touch the filesystem, which
makes a typical built-in import take ~0.15ms rather than 3-5ms.

(Weak links were added in c14a81662c)

This work was funded through GitHub Sponsors.

Signed-off-by: Jim Mussared <jim.mussared@gmail.com>
This commit is contained in:
Jim Mussared
2022-08-17 16:21:03 +10:00
parent 30628d1bb7
commit dfe232d000
9 changed files with 5 additions and 59 deletions
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50
py/builtinimport.c
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@@ -45,15 +45,6 @@
#define DEBUG_printf(...) (void)0
#endif
#if MICROPY_MODULE_WEAK_LINKS
STATIC qstr make_weak_link_name(vstr_t *buffer, qstr name) {
vstr_reset(buffer);
vstr_add_char(buffer, 'u');
vstr_add_str(buffer, qstr_str(name));
return qstr_from_strn(buffer->buf, buffer->len);
}
#endif
#if MICROPY_ENABLE_EXTERNAL_IMPORT
// Must be a string of one byte.
@@ -391,13 +382,8 @@ STATIC mp_obj_t process_import_at_level(qstr full_mod_name, qstr level_mod_name,
if (outer_module_obj == MP_OBJ_NULL) {
DEBUG_printf("Searching for top-level module\n");
// An exact match of a built-in will always bypass the filesystem.
// Note that CPython-compatible built-ins are named e.g. utime, so this
// means that an exact match is only for `import utime`, so `import
// time` will search the filesystem and failing that hit the weak
// link handling below. Whereas micropython-specific built-ins like
// `micropython`, `pyb`, `network`, etc will match exactly and cannot
// be overridden by the filesystem.
// An import of a non-extensible built-in will always bypass the
// filesystem. e.g. `import micropython` or `import pyb`.
module_obj = mp_module_get_builtin(level_mod_name);
if (module_obj != MP_OBJ_NULL) {
return module_obj;
@@ -417,20 +403,9 @@ STATIC mp_obj_t process_import_at_level(qstr full_mod_name, qstr level_mod_name,
// relative to all the locations in sys.path.
stat = stat_top_level(level_mod_name, &path);
#if MICROPY_MODULE_WEAK_LINKS
if (stat == MP_IMPORT_STAT_NO_EXIST) {
// No match on the filesystem. (And not a built-in either).
// If "foo" was requested, then try "ufoo" as a built-in. This
// allows `import time` to use built-in `utime`, unless `time`
// exists on the filesystem. This feature was formerly known
// as "weak links".
qstr umodule_name = make_weak_link_name(&path, level_mod_name);
module_obj = mp_module_get_builtin(umodule_name);
if (module_obj != MP_OBJ_NULL) {
return module_obj;
}
}
#endif
// TODO: If stat failed, now try extensible built-in modules.
// TODO: If importing `ufoo`, try `foo`.
} else {
DEBUG_printf("Searching for sub-module\n");
@@ -667,21 +642,6 @@ mp_obj_t mp_builtin___import___default(size_t n_args, const mp_obj_t *args) {
return module_obj;
}
#if MICROPY_MODULE_WEAK_LINKS
// Check if the u-prefixed name is a built-in.
VSTR_FIXED(umodule_path, MICROPY_ALLOC_PATH_MAX);
qstr umodule_name_qstr = make_weak_link_name(&umodule_path, module_name_qstr);
module_obj = mp_module_get_builtin(umodule_name_qstr);
if (module_obj != MP_OBJ_NULL) {
return module_obj;
}
#elif MICROPY_PY_SYS
// Special handling to make `import sys` work even if weak links aren't enabled.
if (module_name_qstr == MP_QSTR_sys) {
return MP_OBJ_FROM_PTR(&mp_module_sys);
}
#endif
// Couldn't find the module, so fail
#if MICROPY_ERROR_REPORTING <= MICROPY_ERROR_REPORTING_TERSE
mp_raise_msg(&mp_type_ImportError, MP_ERROR_TEXT("module not found"));