…GH-96537)Converting a large enough `int` to a decimal string raises `ValueError` as expected. However, the raise comes _after_ the quadratic-time base-conversion algorithm has run to completion. For effective DOS prevention, we need some kind of check before entering the quadratic-time loop. Oops! =)The quick fix: essentially we catch _most_ values that exceed the threshold up front. Those that slip through will still be on the small side (read: sufficiently fast), and will get caught by the existing check so that the limit remains exact.The justification for the current check. The C code check is:```cmax_str_digits / (3 * PyLong_SHIFT) <= (size_a - 11) / 10```In GitHub markdown math-speak, writing $M$ for `max_str_digits`, $L$ for `PyLong_SHIFT` and $s$ for `size_a`, that check is:$$\left\lfloor\frac{M}{3L}\right\rfloor \le \left\lfloor\frac{s - 11}{10}\right\rfloor$$From this it follows that$$\frac{M}{3L} < \frac{s-1}{10}$$hence that$$\frac{L(s-1)}{M} > \frac{10}{3} > \log_2(10).$$So$$2^{L(s-1)} > 10^M.$$But our input integer $a$ satisfies $|a| \ge 2^{L(s-1)}$, so $|a|$ is larger than $10^M$. This shows that we don't accidentally capture anything _below_ the intended limit in the check.<!-- gh-issue-number:pythongh-95778 -->* Issue:pythongh-95778<!-- /gh-issue-number -->Co-authored-by: Gregory P. Smith [Google LLC] <greg@krypto.org>(cherry picked from commitb126196)Co-authored-by: Mark Dickinson <dickinsm@gmail.com>