STINNER Victor added the comment:
To access an array item, the type of the index variable must be size_t (or a
type with the same size), otherwise the compiler produce less efficient machine
code:
http://www.viva64.com/en/a/0050/
=> please keep Py_ssize_t type for i
(I didn't check for the specific case of Py_ssize_t: it's signed. Does GCC emit
the most efficient machine code for it?)
diff -r 16c8278c03f6 Modules/_pickle.c
--- a/Modules/_pickle.c
+++ b/Modules/_pickle.c
@@ -4606,10 +4606,17 @@ static Py_ssize_t
calc_binsize(char *bytes, int nbytes)
{
unsigned char *s = (unsigned char *)bytes;
- Py_ssize_t i;
+ int i;
size_t x = 0;
- for (i = 0; i < nbytes && (size_t)i < sizeof(size_t); i++) {
+ if (nbytes > (int)sizeof(size_t)) {
+ for (i = (int)sizeof(size_t); i < nbytes; i++) {
+ if (s[i])
+ return -1;
+ }
+ nbytes = (int)sizeof(size_t);
+ }
Please add a comment here to explain that the first loop check for integer
overflow, it's not obvious at the first read.
Does the Python implementation of pickle produce BINBYTES8? If not: why not?
Note: the patch is probably based on a private Mercurial revision, so it didn't
get the [Review] button.
----------
nosy: +haypo
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