1 files changed, 25 insertions, 0 deletions
diff --git a/libevent/cmake/CheckConstExists.cmake b/libevent/cmake/CheckConstExists.cmake
new file mode 100644
index 0000000..de07458
--- /dev/null
+++ b/libevent/cmake/CheckConstExists.cmake
@@ -0,0 +1,25 @@
+include(CheckCSourceCompiles)
+
+macro(check_const_exists CONST FILES VARIABLE)
+  if (NOT DEFINED ${VARIABLE})
+    set(check_const_exists_source "")
+    foreach(file ${FILES})
+      set(check_const_exists_source
+          "${check_const_exists_source}
+          #include <${file}>")
+    endforeach()
+    set(check_const_exists_source
+        "${check_const_exists_source}
+        int main() { (void)${CONST}; return 0; }")
+
+    check_c_source_compiles("${check_const_exists_source}" ${VARIABLE})
+
+    if (${${VARIABLE}})
+      set(${VARIABLE} 1 CACHE INTERNAL "Have const ${CONST}")
+      message(STATUS "Looking for ${CONST} - found")
+    else()
+      set(${VARIABLE} 0 CACHE INTERNAL "Have const ${CONST}")
+      message(STATUS "Looking for ${CONST} - not found")
+    endif()
+  endif()
+endmacro(check_const_exists)