[chenshi5012]

What type of PR is this?

• bug
• feature
• enhancement

What problem(s) does this PR solve?

Issue(s) number: #147

Description:

The SessionPool move constructor transfers the configuration and the underlying ConnectionPool, but does not transfer idleSessions_.

As a result, the moved-to pool has no idle sessions and requests can fail with No idle session.. Meanwhile, the moved-from pool retains Session wrappers that hold raw pointers to the underlying connection pool. If the moved-to pool is destroyed first, those pointers may become dangling, creating a potential use-after-free during destruction of the moved-from pool.

How do you solve it?

Move idleSessions_ along with the configuration and the underlying ConnectionPool in the SessionPool move constructor. This keeps the idle sessions with the pool that owns their connection pool and leaves the moved-from pool without those session wrappers.

Special notes for your reviewer, ex. impact of this fix, design document, etc:

• Added the regression test SessionPoolTest.MoveConstructorTransfersIdleSessions.
• The test initializes a one-slot pool, move-constructs a destination pool, executes YIELD 1 on the destination, and destroys the destination before the source.
• The session_pool_test target built successfully, and the focused regression test passed.
• No separate ASan run was performed to capture the potential use-after-free.

Fixes #147

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