[davlgd]

Fixes #621

Motivation

With GCC 15.3.0 and 16.2.1 at -O2, testAllocatedContents in tests/MessageTest.cc fails to compile under the project's -Werror setting. It uses strncpy to copy str.length() bytes, omitting the terminating NUL. The test passes the buffer with an explicit byte count, so a NUL terminator is not required: memcpy expresses the intended byte copy without triggering -Wstringop-truncation.

Modifications

Replace strncpy with memcpy for the same str.length() bytes. The content and length passed to the message are unchanged.

Verifying this change

• Make sure that the change passes the CI checks.

This change is already covered by existing tests, such as MessageTest.testAllocatedContents, which builds and passes with the change.

Documentation

• doc-not-needed
  (Only the setup of an existing test changes; no public API or user-facing behavior changes.)