CMake-3.31.8-GCCcore-14.3.0 bootstrap fails on Intel Granite Rapids / GCC 14.3: "-mavx10.1" warning trips cm_cxx_features feature checks

[ejames604]

Summary

CMake-3.31.8-GCCcore-14.3.0.eb (and 4.0.3-GCCcore-14.3.0, likely the same root
cause) fails to bootstrap on Intel CPUs where -march=native enables -mavx10.1
(Granite Rapids, future Sapphire Rapids etc.). Bootstrap dies with:

CMake Error at CMakeLists.txt:93 (message):
The C++ compiler does not support C++11 (e.g. std::unique_ptr).

— even though the compiler does support C++11 and the test programs compile +
link + run by hand.

Affected configuration

• CMake version: 3.31.8 (3.31.3 works); 4.0.3 presumed affected (same
  empty-install symptom, not yet confirmed)
• Toolchain: GCCcore-14.3.0 (foss-2025b)
• Host CPU: Intel Granite Rapids (Xeon 6760P) — any Intel chip where
  -march=native enables -mavx10.1
• EB: 5.2.1 (also reproduces with 5.1.x, 5.3.0)
• AMD Zen4 / Zen5: unaffected (the trigger warning never appears)

Root cause

Source/Checks/cm_cxx_features.cmake applies a chain of string(REGEX REPLACE
...) filters to strip known warning lines from check output (ninja, ld,
MSBuild, distcc, …), then runs a catch-all:

If using the feature causes warnings, treat it as broken/unavailable.

if(check_output MATCHES "(^|[ :])[Ww][Aa][Rr][Nn][Ii][Nn][Gg]")
set(CMake_HAVE_CXX_${FEATURE} OFF CACHE INTERNAL "TRY_COMPILE" FORCE)
endif()

The filter list does not strip cc1plus: warning: from GCC. On Granite Rapids,
GCC 14.3 emits on every compile:

cc1plus: warning: '-mavx10.1' is aliased to 512 bit since GCC14.3

…because -march=native enables -mavx10.1. The line passes every filter and
triggers the catch-all, marking make_unique, unique_ptr, and filesystem all as
"broken" — bootstrap aborts at CMakeLists.txt:93.

Reproducer

On a Granite Rapids host (or any Intel CPU that enables -mavx10.1 via
-march=native):

module load EasyBuild/5.2.1
eb CMake-3.31.8-GCCcore-14.3.0.eb

Watch CMakeFiles/CMakeError.log under the build dir:

each cm_cxx_*.cxx try_compile transcript contains

"cc1plus: warning: '-mavx10.1' is aliased to 512 bit since GCC14.3"

and CMake declares the feature broken.

Compile + link + execute of the same Source/Checks/cm_cxx_make_unique.cxx by
hand exits 0. A try_compile() of the same source from a custom CMakeLists.txt
(which bypasses cm_check_cxx_feature) also succeeds — even with the half-built
Bootstrap.cmk/cmake (3.31.8's own check binary) as the driver. So the failure
is specifically in cm_check_cxx_feature's warning-filter logic, not the
compiler chain.

Suggested fix (verified locally)

Add one filter line to the chain in Source/Checks/cm_cxx_features.cmake:

   # Filter out distcc.
   string(REGEX REPLACE "[^\n]*distcc\\[[0-9]+\\][^\n]*[Ww]arning:[^\n]*" ""

check_output "${check_output}")

• Filter out GCC's benign "-mavx10.x is aliased to N bit" cc1/cc1plus

warnings.

• string(REGEX REPLACE "[^\n]cc1[a-z]: warning: '-mavx10\.[0-9]+' is
  aliased to[^\n]*" "" check_output "${check_output}")

  If using the feature causes warnings, treat it as broken/unavailable.

  if(check_output MATCHES "(^|[ :])[Ww][Aa][Rr][Nn][Ii][Nn][Gg]")

End-to-end verified: with this patch in place,
cm_check_cxx_feature(make_unique) and (filesystem) return yes, and Configuring
done. Build proceeds normally.

Upstream

The bug is in CMake itself — the filter list is missing cc1plus:. Worth filing
at Kitware/CMake too. For EB users, a downstream patch in the EB recipes
seems like the right interim fix until upstream addresses it.

Workarounds without patching

• Use CMake-3.31.3-GCCcore-14.3.0 (predates whatever filter-list change
  introduced the regression; works fine on Granite Rapids).
• Override optarch for the CMake build so -mavx10.1 is never enabled
  (toolchainopts = {'optarch': '-march=x86-64-v3'} or similar). Loses Granite
  Rapids tuning of the CMake binary, which is fine — CMake is a build tool.

[Thyre]

Should be solved by easybuilders/easybuild-easyconfigs#25731, which will be part of the next EasyBuild release (and can be installed via --from-pr in the meantime).