have_const(const, headers = nil, opt = "", &b)public
Returns whether or not the constant const is defined. You may optionally pass the type of const as [const, type], like as:
have_const(%w[PTHREAD_MUTEX_INITIALIZER pthread_mutex_t], "pthread.h")
You may also pass additional headers to check against in addition to the common header files, and additional flags to opt which are then passed along to the compiler.
If found, a macro is passed as a preprocessor constant to the compiler using the type name, in uppercase, prepended with ‘HAVE_CONST_’.
For example, if have_const(‘foo’) returned true, then the HAVE_CONST_FOO preprocessor macro would be passed to the compiler.
# File lib/mkmf.rb, line 984 def have_const(const, headers = nil, opt = "", &b) checking_for checking_message([*const].compact.join(' '), headers, opt) do try_const(const, headers, opt, &b) end end