[Python-Dev] Replace useless %.100s by %s in PyErr_Format()

[Victor Stinner]

Hi,

I plan to replace all %.100s (or any other size, %\.[0-9]+s regex) by %s
in the whole source code, in all calls to PyErr_Format(). And I would
like your opinion.

When Guido added the function PyErr_Format(), 13 years ago, the function
was implemented using a buffer of 500 bytes (allocated on the stack).
The developer was responsible to limit the argument fit into a total of
500 bytes. But 3 years later (2000), PyErr_Format() was patched to use a
dynamic buffer (allocated on the heap). But since this change,
PyErr_Format() doesn't support %.100s anymore (the 100 bytes limitation
is just ignored), and it becomes useless and so no, it's no more (since
10 years) a "protection" against segmentation fault.

But I would like to know if I have to do in all branches (3.1-3.3, or
worse: 2.5-3.3), or just in 3.3? Because it may make merge harder (like
any change only done in default).

I would like to replace %.100s because there are no more reason to
truncate strings to an arbitrary length.

=> http://bugs.python.org/issue10833

---

... at the same time, Ray Allen wrote a patch to implement %.100s in
PyUnicode_FromFormatV() (so PyErr_Format() will support it too). I would
like to replace %.100s in PyErr_Format(), and then commit its patch.

http://bugs.python.org/issue7330

Victor