tree 51292d19942bca36e341cf2075fbda7247e7f157
parent 73d2688300440c8af028eec865ee0dcd85e93025
author Sayed Nabhan <nabhan@bugqore.com> 1789778566 -0700
committer Copybara-Service <copybara-worker@google.com> 1789778606 -0700

PR #2144: validate log_uniform_int_distribution stream input and harden preconditions

Imported from GitHub PR https://github.com/abseil/abseil-cpp/pull/2144

log_uniform_int_distribution's param_type constructor computes log_range_ as static_cast<int>(ceil((1/log(base)) * log(range))). A base of 0 or 1, or a negative base for a signed IntType, violates the base > 1 precondition and makes that math non-finite: 1/log(1) divides by zero, and the final cast of inf/NaN to int is undefined behavior (UBSan: "inf is outside the range of representable values of type 'int'"). It was also reachable through operator>>, which handed whatever it parsed straight to param_type.

Changes:
- Check the param_type preconditions with ABSL_HARDENING_ASSERT.
- Only take the log() branch for base_ > 2, so an out-of-contract base never reaches the floating-point math.
- Have operator>> validate max >= min and base > 1 and set failbit on bad input instead of constructing an invalid param_type, with a test covering that rejection.

Merge b15918e1696ac26b2f283a26c03671a29f9b61a6 into 8bd6e5097d96974f5c85031759c545a8e7426b4a

Merging this change closes #2144

PiperOrigin-RevId: 984157679
Change-Id: I003a3dd5536fdac5731850017095915e73ab05bb