nc: set a variable to point to this directory

link_flag.cmake

@@ -12,7 +12,7 @@ macro(check_link_flag _variable _flag)
             __check_link_flag_${_name}
             "${CMAKE_CURRENT_BINARY_DIR}/CMakeTmp"
         SOURCES
-            "${CMAKE_CURRENT_SOURCE_DIR}/cmake/test_link_flag.cpp")
+            "${NC_CMAKE_BASE}/test_link_flag.cpp")
 
         if (__check_link_flag_${_name})
             message (STATUS "checking linker flag ${_flag} - found")

nc.cmake

@@ -13,6 +13,20 @@ set (THREADS_PREFER_PTHREAD_FLAG ON)
 find_package (Threads REQUIRED)
 link_libraries (Threads::Threads)
 
+# Set the variable NC_CMAKE_BASE to the root path of this collection of cmake
+# files so that we can reliably point to soure files contained therein
+# (eg, the search_lib.cpp tests and friends).
+foreach (d ${CMAKE_MODULE_PATH})
+    message (STATUS testing nc_cmake_base at "${d}")
+    if (EXISTS "${d}/nc.cmake")
+        set (NC_CMAKE_BASE "${d}")
+        message (STATUS testing nc_cmake_base at "${d} - found")
+        break()
+    else ()
+        message (STATUS testing nc_cmake_base at "${d} - not found")
+    endif ()
+endforeach()
+
 include (nc_cxx)
 include (nc_sanitizer)
 include (nc_platform)

search_libs.cmake

@@ -21,7 +21,7 @@ macro(search_libs _variable _symbol)
                 __search_libs_${_symbol}
                 "${CMAKE_BINARY_DIR}/CMakeTmp"
             SOURCES
-                "${CMAKE_SOURCE_DIR}/cmake/search_libs.cpp"
+                "${NC_CMAKE_BASE}/search_libs.cpp"
             COMPILE_DEFINITIONS
                 "-DSYMBOL=${_symbol}")
 
@@ -36,7 +36,7 @@ macro(search_libs _variable _symbol)
                             __search_libs_${_symbol}
                             "${CMAKE_BINARY_DIR}/CMakeTmp"
                         SOURCES
-                            "${CMAKE_SOURCE_DIR}/cmake/search_libs.cpp"
+                            "${NC_CMAKE_BASE}/search_libs.cpp"
                         LINK_LIBRARIES
                             "${lib}"
                         COMPILE_DEFINITIONS

test_restrict.cmake

@@ -6,7 +6,7 @@ macro(test_restrict VARIABLE)
                 TRY_COMPILE(
                     TEST_${VARIABLE}
                     "${CMAKE_BINARY_DIR}/CMakeTmp"
-                    SOURCES "${CMAKE_SOURCE_DIR}/cmake/test_restrict.cpp"
+                    SOURCES "${NC_CMAKE_BASE}/test_restrict.cpp"
                     COMPILE_DEFINITIONS "-DKEYWORD=${KEYWORD}")
                 set(__test_restrict_last ${KEYWORD})
             ENDIF (NOT TEST_${VARIABLE})