Enforce 64-bit requirement. (#311)

Signed-off-by: Samuel K. Gutierrez <[email protected]>

cmake/QVCheckTypes.cmake

@@ -1,5 +1,5 @@
 #
-# Copyright (c)      2022 Triad National Security, LLC
+# Copyright (c) 2022-2025 Triad National Security, LLC
 #                         All rights reserved.
 #
 # This file is part of the quo-vadis project. See the LICENSE file at the
@@ -9,6 +9,17 @@
 # Checks size of data types.
 include(CheckTypeSize)
 
+# We only support 64-bit architectures and builds. This is primarily because
+# hwloc relies on a large virtual address space for its shared-memory
+# sub-system.
+message(CHECK_START "Verifying that this is a 64-bit+ build")
+if(CMAKE_SIZEOF_VOID_P LESS_EQUAL 4)
+    math(EXPR QV_BUILD_BITS "${CMAKE_SIZEOF_VOID_P} * 8" OUTPUT_FORMAT DECIMAL)
+    message(FATAL_ERROR "${QV_BUILD_BITS}-bit builds are not supported")
+else()
+    message(CHECK_PASS "verified")
+endif()
+
 check_type_size(int QVI_SIZEOF_INT)
 check_type_size(pid_t QVI_SIZEOF_PID_T)