Fix Linux MKL build 3

Author: daleroberts

.github/workflows/build.yml

@@ -146,7 +146,8 @@ jobs:
       - name: Build with CMake
         run: |
           source /opt/intel/oneapi/setvars.sh
-          cmake dynadjust -DUSE_MKL=ON -DBUILD_TESTING=OFF -DUSE_UNITY_BUILD=ON
+          cmake dynadjust -DUSE_MKL=ON -DBUILD_TESTING=OFF -DUSE_UNITY_BUILD=ON \
+            -DCMAKE_CXX_FLAGS="-UMKL_ILP64" -DCMAKE_C_FLAGS="-UMKL_ILP64"
           make -j2
           ls -la bin/
 

dynadjust/CMakeLists.txt

@@ -348,6 +348,17 @@ else()
         # Use Intel MKL's native CMake config
         add_compile_options("-DUSE_MKL")
 
+        # Explicitly control the MKL interface at compile time
+        if(NOT ILP64)
+            # Undefine MKL_ILP64 to prevent OneAPI environment from forcing ILP64
+            # Use CMAKE_CXX_FLAGS to ensure this is applied early
+            set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -UMKL_ILP64")
+            set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -UMKL_ILP64")
+            message(STATUS "LP64 interface selected: added -UMKL_ILP64 to compiler flags")
+        else()
+            message(STATUS "ILP64 interface selected")
+        endif()
+
         # Use FindBLAS to locate Intel MKL with explicit interface selection
         # Note: MKLConfig.cmake in OneAPI 2025.x has issues with interface selection,
         # so we use FindBLAS which allows explicit LP64/ILP64 selection via BLA_VENDOR