check_c_source_compiles("
  #include <stdio.h>
  int main(void) {
    double a = 0.0;
    #if defined(__has_attribute)
    # if !__has_attribute(assume)
    #   error no assume
    # endif
    #else
    #error no __has_attribute
    #endif
    __attribute__((assume(a >= 0.0)));
    a = a + 1.0;
    printf(\"a=%g\", a);
    return 0;
  }
" SUNDIALS_C_COMPILER_HAS_ATTRIBUTE_ASSUME)