### Summary #33840 adjusted `V2TransportTester::SendMessage` to avoid a `-Warray-bounds` false positive with **GCC 13**, but **GCC 15.2** still warns. ### Fix Implemented the suggestion in https://github.com/bitcoin/bitcoin/pull/33840#pullrequestreview-3447477940: - take `mtype` as `std::string_view`; - assert `mtype.size() <= CMessageHeader::MESSAGE_TYPE_SIZE`; - build `[0x00][12-byte type][payload]` via `std::ranges::copy`. ### Reproducer Before this change, using GCC 15.2 on a Mac > rm -rfd build && cmake -B build -DENABLE_IPC=OFF -DCMAKE_C_COMPILER=gcc -DCMAKE_CXX_COMPILER=g++ && cmake --build build -j$(nproc) produces: ```bash [100%] Building CXX object src/test/CMakeFiles/test_bitcoin.dir/__/wallet/test/walletload_tests.cpp.o In file included from /opt/homebrew/Cellar/gcc/15.2.0/include/c++/15/array:45, from /opt/homebrew/Cellar/gcc/15.2.0/include/c++/15/span:46, from /Users/lorinc/bitcoin/src/span.h:10, from /Users/lorinc/bitcoin/src/uint256.h:10, from /Users/lorinc/bitcoin/src/consensus/params.h:10, from /Users/lorinc/bitcoin/src/kernel/chainparams.h:9, from /Users/lorinc/bitcoin/src/chainparams.h:9, from /Users/lorinc/bitcoin/src/test/net_tests.cpp:5: In function 'constexpr _OutIter std::__copy_move_a2(_InIter, _Sent, _OutIter) [with bool _IsMove = false; _InIter = char*; _Sent = char*; _OutIter = unsigned char*]', inlined from 'constexpr _OI std::__copy_move_a1(_II, _II, _OI) [with bool _IsMove = false; _II = char*; _OI = unsigned char*]' at /opt/homebrew/Cellar/gcc/15.2.0/include/c++/15/bits/stl_algobase.h:492:42, inlined from 'constexpr _OI std::__copy_move_a(_II, _II, _OI) [with bool _IsMove = false; _II = __gnu_cxx::__normal_iterator >; _OI = __gnu_cxx::__normal_iterator >]' at /opt/homebrew/Cellar/gcc/15.2.0/include/c++/15/bits/stl_algobase.h:500:31, inlined from 'constexpr _OI std::copy(_II, _II, _OI) [with _II = __gnu_cxx::__normal_iterator >; _OI = __gnu_cxx::__normal_iterator >]' at /opt/homebrew/Cellar/gcc/15.2.0/include/c++/15/bits/stl_algobase.h:642:7, inlined from 'void net_tests::{anonymous}::V2TransportTester::SendMessage(std::string, std::span)' at /Users/lorinc/bitcoin/src/test/net_tests.cpp:1304:18: /opt/homebrew/Cellar/gcc/15.2.0/include/c++/15/bits/stl_algobase.h:426:32: warning: 'void* __builtin_memmove(void*, const void*, long unsigned int)' offset [0, 1] is out of the bounds [0, 0] [-Warray-bounds=] 426 | __builtin_memmove(_GLIBCXX_TO_ADDR(__result), | ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~ 427 | _GLIBCXX_TO_ADDR(__first), | ~~~~~~~~~~~~~~~~~~~~~~~~~~ 428 | __n * sizeof(*__first)); | ~~~~~~~~~~~~~~~~~~~~~~~ [100%] Linking CXX executable ../../bin/test_bitcoin ```

test: tighten `V2TransportTester::SendMessage` bounds for GCC 15.2