# tests for compiler properties
-CHECK_C_SOURCE_COMPILES("int foo(int) __attribute__ ((ifunc(\"foo_i\"))); int f1(int i) { return i; } void (*foo_i()) { return f1; } int main(void) { return 0; }" HAS_C_ATTR_IFUNC)
+# set -Werror so we can't ignore unused attribute warnings
+set (CMAKE_REQUIRED_FLAGS "-Werror")
+
+CHECK_C_SOURCE_COMPILES("
+ int foo(int) __attribute__ ((ifunc(\"foo_i\")));
+ int f1(int i) { return i; }
+ void (*foo_i()) { return f1; }
+ int main(void) { return 0; }
+ " HAS_C_ATTR_IFUNC)
+
+unset(CMAKE_REQUIRED_FLAGS)