py/persistentcode.c: Explain the "special" fixed QSTRs.

jimmo · jimmo · commit e3d2ffeacaaf · 2023-10-09T13:37:43.000+11:00
These are part of the .mpy ABI and avoid needing to duplicate string
data for QSTRs known to already be in the firmware.

Signed-off-by: Jim Mussared &lt;jim.mussared@gmail.com&gt;
diff --git a/py/makeqstrdata.py b/py/makeqstrdata.py
@@ -52,7 +52,8 @@
 codepoint2name[ord("|")] = "pipe"
 codepoint2name[ord("~")] = "tilde"
 
-# static qstrs, should be sorted
+# static qstrs, these must maintain a specific order for .mpy compatibility
+# See QSTR_LAST_STATIC at the top of py/persistentcode.c
 
 static_qstr_list = [
     "",
diff --git a/py/persistentcode.c b/py/persistentcode.c
@@ -40,6 +40,11 @@
 
 #include "py/smallint.h"
 
+// makeqstrdata.py has a fixed list of qstrs at the start that we can assume
+// are available with know indices on all MicroPython implementations, and
+// avoid needing to duplicate the string data in the .mpy file. This is the
+// last one in that list (anything with a qstr less than or equal to this is
+// assumed to be in the list).
 #define QSTR_LAST_STATIC MP_QSTR_zip
 
 #if MICROPY_DYNAMIC_COMPILER
