这个 C 语言声明是什么意思？

Question

int (*EVP_MD_meth_get_cleanup(const EVP_MD *md))(EVP_MD_CTX *ctx)

I find this code piece, not sure how to understand it. I think EVP_MD_meth_get_cleanup is the name of the function pointer type, return int , but not understand the argument part.

Answer 1

EVP_MD_meth_get_cleanup is a function, that takes const EVP_MD *md as an argument, and returns a function pointer . That function pointer takes EVP_MD_CTX *ctx and returns an int .

Nothing better than an example:

int somefunction(EVP_MD_CTX *ctx) {
    stuff();
}

int (*EVP_MD_meth_get_cleanup(const EVP_MD *md))(EVP_MD_CTX *ctx) {
   return somefunction;
}