tests : qualify isnan and signbit with std:: (#31791)
* tests : qualify isnan and signbit with std::
The unqualified calls rely on the C math.h names also being present in the
global namespace, which is not the case for the NetBSD 11.99.9/x86_64 gcc
14.4.0 build reported in the issue. Prefix the calls with std:: to select
the standard C++ overloads declared by <cmath>.
ref: https://github.com/ggml-org/ggml/issues/1681
Assisted-by: dsh:llama.cpp/ggml-org/Qwen3.8-Flash-Next-GGUF (MacBook, M5 Max, 128GB)
* tests : qualify C math calls with std::
Follow-up to the isnan / signbit fix: make the remaining math calls in
test-quantize-fns.cpp consistent with the std:: isfinite / max / numeric_limits
already used in the same file.
The float variants are overloads in C++, not distinct names, so the mapping is
fabsf -> std::fabs, copysignf -> std::copysign, nextafterf -> std::nextafter -
not std::fabsf & friends, which do not exist in libstdc++ and would break the
gcc build. NAN and INFINITY are macros and are left unqualified.
Only behavioural difference: array_rmse() fed a double accumulator to sqrtf(),
now std::sqrt() keeps the computation in double. The result is more accurate
and differs from the previous value by at most 1.4e-7 relative, three orders of
magnitude below the tightest tolerance in this test.
Assisted-by: dsh:llama.cpp/ggml-org/Qwen3.8-Flash-Next-GGUF (MacBook, M5 Max, 128GB)
