fix: Fix undefined behavior in BinarySection bitmask constants caused by signed left shift

[lxy-9602]

Purpose

No Linked issue.

What is the problem?

In BinarySection, the bitmask constants HIGHEST_FIRST_BIT and HIGHEST_SECOND_TO_EIGHTH_BIT are defined using signed left shift:

static constexpr int64_t HIGHEST_FIRST_BIT = 0x80L << 56;
static constexpr int64_t HIGHEST_SECOND_TO_EIGHTH_BIT = 0x7FL << 56;

0x80L is a signed long with value 128. Left-shifting it by 56 bits overflows into the sign bit of a 64-bit signed integer, which is undefined behavior (UB) per the C++ standard (before C++20, and still implementation-defined in C++20).

What is the fix?

Use unsigned literals (0x80ULL, 0x7FULL) for the shift operation to ensure defined behavior, then static_cast back to int64_t:

static constexpr int64_t HIGHEST_FIRST_BIT = static_cast<int64_t>(0x80ULL << 56);
static constexpr int64_t HIGHEST_SECOND_TO_EIGHTH_BIT = static_cast<int64_t>(0x7FULL << 56);

Tests

API and Format

Documentation

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