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Saves 16 bytes of code on a Cortex M0 and 7 bytes in the .mpy file.
This costs 20 bytes on a Cortex-M0 but saves 94 bytes of file size in the modx example.
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This is superseded by micropython#5083 |
dpgeorge
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May 30, 2021
asan considers that memcmp(p, q, N) is permitted to access N bytes at each
of p and q, even for values of p and q that have a difference earlier.
Accessing additional values is frequently done in practice, reading 4 or
more bytes from each input at a time for efficiency, so when completing
"non_exist<TAB>" in the repl, this causes a diagnostic:
==16938==ERROR: AddressSanitizer: global-buffer-overflow on
address 0x555555cd8dc8 at pc 0x7ffff726457b bp 0x7fffffffda20 sp 0x7fff
READ of size 9 at 0x555555cd8dc8 thread T0
#0 0x7ffff726457a (/usr/lib/x86_64-linux-gnu/libasan.so.5+0xb857a)
#1 0x555555b0e82a in mp_repl_autocomplete ../../py/repl.c:301
#2 0x555555c89585 in readline_process_char ../../lib/mp-readline/re
#3 0x555555c8ac6e in readline ../../lib/mp-readline/readline.c:513
#4 0x555555b8dcbd in do_repl /home/jepler/src/micropython/ports/uni
#5 0x555555b90859 in main_ /home/jepler/src/micropython/ports/unix/
#6 0x555555b90a3a in main /home/jepler/src/micropython/ports/unix/m
#7 0x7ffff619a09a in __libc_start_main ../csu/libc-start.c:308
#8 0x55555595fd69 in _start (/home/jepler/src/micropython/ports/uni
0x555555cd8dc8 is located 0 bytes to the right of global variable
'import_str' defined in '../../py/repl.c:285:23' (0x555555cd8dc0) of
size 8
'import_str' is ascii string 'import '
Signed-off-by: Jeff Epler <[email protected]>
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Do not load qstrs from within the init function, but put them in a separate area of the .mpy file (with a more efficient encoding). This reduces the size of the .mpy file (94 bytes in the modx example), but increases the code size by 20 bytes on a Cortex-M0. I've also done another optimization which reduces code size by 16 bytes (net increase is thus 4 bytes).