Determine lapack fortran linking convention in CMake (#934)

* Determine lapack fortran linking convention in CMake

Looks for lapack function with and without trailing underscore - allows use of CLAPACK on windows where functions are decorated but fortran_id.h otherwise assumes they are not

* Use enable_preprocessor_switch for LAPACK decoration detection

* Add lapack decoration defines to config.h.in

* Use correct variable for lapack_libraries

dlib/CMakeLists.txt

@@ -502,6 +502,13 @@ if (NOT TARGET dlib)
          if (DLIB_USE_LAPACK)
             if (lapack_found)
                set (dlib_needed_libraries ${dlib_needed_libraries} ${lapack_libraries})
+               if (lapack_with_underscore)
+                  set(LAPACK_FORCE_UNDERSCORE 1)
+                  enable_preprocessor_switch(LAPACK_FORCE_UNDERSCORE)
+               elseif (lapack_without_underscore)
+                  set(LAPACK_FORCE_NOUNDERSCORE 1)
+                  enable_preprocessor_switch(LAPACK_FORCE_NOUNDERSCORE)
+               endif ()
             else()
                set(DLIB_USE_LAPACK OFF CACHE STRING ${DLIB_USE_LAPACK_STR} FORCE )
                toggle_preprocessor_switch(DLIB_USE_LAPACK)

dlib/cmake_utils/cmake_find_blas.txt

@@ -26,6 +26,8 @@ SET(blas_found 0)
 SET(lapack_found 0)
 SET(found_intel_mkl 0)
 SET(found_intel_mkl_headers 0)
+SET(lapack_with_underscore 0)
+SET(lapack_without_underscore 0)
 
 message(STATUS "Searching for BLAS and LAPACK")
 
@@ -346,3 +348,22 @@ if (NOT lapack_found)
     endif()
 endif()
 
+# If using lapack, determine whether to mangle functions
+if (lapack_found)
+   include(CheckFunctionExists)
+   include(CheckFortranFunctionExists)
+   set(CMAKE_REQUIRED_LIBRARIES ${lapack_libraries})
+
+   check_function_exists("sgesv" LAPACK_FOUND_C_UNMANGLED)
+   check_function_exists("sgesv_" LAPACK_FOUND_C_MANGLED)
+   if (CMAKE_Fortran_COMPILER_LOADED)
+      check_fortran_function_exists("sgesv" LAPACK_FOUND_FORTRAN_UNMANGLED)
+      check_fortran_function_exists("sgesv_" LAPACK_FOUND_FORTRAN_MANGLED)
+   endif ()
+   if (LAPACK_FOUND_C_MANGLED OR LAPACK_FOUND_FORTRAN_MANGLED)
+      set(lapack_with_underscore 1)
+   elseif (LAPACK_FOUND_C_UNMANGLED OR LAPACK_FOUND_FORTRAN_UNMANGLED)
+      set(lapack_without_underscore 1)
+   endif ()
+endif()
+

dlib/config.h.in

@@ -14,6 +14,9 @@
 #cmakedefine DLIB_NO_GUI_SUPPORT
 #cmakedefine DLIB_ENABLE_STACK_TRACE
 
+#cmakedefine LAPACK_FORCE_UNDERSCORE
+#cmakedefine LAPACK_FORCE_NOUNDERSCORE
+
 // You should also consider telling dlib to link against libjpeg, libpng, libgif, fftw, CUDA, 
 // and a BLAS and LAPACK library.  To do this you need to uncomment the following #defines.
 #cmakedefine DLIB_JPEG_SUPPORT

dlib/matrix/lapack/fortran_id.h

@@ -18,7 +18,11 @@
 
 // First we need to know what the conventions for linking
 // C with Fortran is on this platform/toolset
-#if defined(__GNUC__) || defined(__ICC) || defined(__sgi) || defined(__COMO__) || defined(__KCC)
+#if defined(LAPACK_FORCE_UNDERSCORE)
+#define DLIB_BIND_FORTRAN_LOWERCASE_UNDERSCORE
+#elif defined(LAPACK_FORCE_NOUNDERSCORE)
+#define DLIB_BIND_FORTRAN_LOWERCASE
+#elif defined(__GNUC__) || defined(__ICC) || defined(__sgi) || defined(__COMO__) || defined(__KCC)
 #define DLIB_BIND_FORTRAN_LOWERCASE_UNDERSCORE
 #elif defined(__IBMCPP__) || defined(_MSC_VER) || defined(__BORLANDC__)
 #define DLIB_BIND_FORTRAN_LOWERCASE