让我有一个标题，例如#include.它包含OpenGLAPI函数的子集。我需要这样的东西:static_assert(has_glDrawArraysIndirect::value,"ThereisnoglDrawArraysIndirect");或者更好:PFNGLDRAWARRAYSINSTANCEDPROCptr_glDrawArraysIndirect=ptr_to_glDrawArraysIndirect::ptr;在哪里ptr_to_glDrawArraysIndirect::ptr展开指向glDrawArraysIndirect的指针(如果已定义)或stub函数stub