Add a valgrind suppression file for the tests

[derobins]

test/valgrind.supp suppresses the "still reachable" blocks that valgrind reports in the unit tests and examples when it's run with --show-leak-kinds=reachable or all. None of them come from a bug in hipObject; each is memory that a library allocates once and keeps until the process exits:

• The static constructors in ROCm's libLLVM and libclang-cpp, which the HIP runtime loads
• The HIP runtime, while it's being loaded and during its one-time setup on the first HIP call (including hsa_init())
• systemPlatform(), which never destroys its platform, and the dynamic loader's records of libibverbs, which the platform keeps loaded
• OpenSSL's global state, which it keeps after curl_global_cleanup()

Every entry matches only reachable blocks, so definite, indirect, and possible leaks are always reported. The HIP and systemPlatform() entries match only allocations made under the function that does the one-time setup, so the same allocations made anywhere else are still reported. Some of those stacks are about 20 frames deep, so the file says to run valgrind with --num-callers=40 or more.

The file also says that valgrind can't run optimized Clang builds of hipObject correctly. With -ftrivial-auto-var-init=pattern, which hipObject's Clang options always add, Clang at -O1 and above copies std::format()'s arguments with the x87 instructions fldt and fstpt. Valgrind emulates the x87 registers with 64 bits instead of 80, so the copy loses bits: std::format("{}", 42) returns "0", and formatting a string can crash. A five-line std::format() program reproduces it, even with --tool=none, and runs correctly natively and with GCC. GCC builds and Clang Debug builds work.

Testing: ran ctest -T memcheck on the 26 unit tests and the get-version example with --leak-check=full --show-leak-kinds=all --errors-for-leak-kinds=all --num-callers=40, with ROCm 10.1 and valgrind 3.26. GCC Debug and Clang Debug builds passed 27/27, with no errors and no blocks still reachable. Without the file, all 27 fail. codespell is clean.

[github-actions]

Security scan found no critical or high findings on lines changed by this pull request

View the security scan run for complete reports.

“New” means the finding is located in a changed file on an added or modified line; it is not a base-versus-head findings delta.

[Copilot]

🟢 Approval recommended

The suppressions preserve lost-memory diagnostics, introduce no runtime changes, and have no unresolved findings.

No open issues 🎉

What changed in this PR

Adds Valgrind suppressions for expected library allocations retained until process exit, keeping test memory reports focused on actionable leaks.

Changes:

• Suppresses only reachable allocations, preserving all lost-memory diagnostics.
• Documents CTest usage, required stack depth, and optimized Clang limitations.

File	Description
test/​valgrind.supp	Adds scoped suppressions and instructions for memory checks.

_{Review effort: Balanced}