using secp256k1_sha256 internal api

libsecp_sha256.c

/* this is the main function of test.c of libsecp */
/* you can find my complete code here: https://github.com/siv2r/secp256k1/commit/b3a1437f715dad7478515a55728ecb12aaf4dad1 */

#include "modules/debug/main_impl.h"

int main() {
    unsigned char msg[40] = "Hey, this message is going to be hashed";
    unsigned char out[32];
    secp256k1_sha256 hash;

    printf("message        : %s\n", msg);

    secp256k1_sha256_initialize(&hash);
    printf("sha256 (init)  : ");
    print_sha(&hash); // prints the 256 bit hash.s array

    secp256k1_sha256_write(&hash, msg, 40);
    printf("sha256 (write) : ");
    print_sha(&hash);

    secp256k1_sha256_finalize(&hash, out);
    printf("sha256         : ");
    print_sha(&hash);

    printf("out            : ");
    print_buf(out, 32); 
}

output.txt

message          : Hey, this message is going to be hashed
sha256 (init)    : 6a09e667 bb67ae85 3c6ef372 a54ff53a 510e527f 9b05688c 1f83d9ab 5be0cd19 
sha256 (write)   : 6a09e667 bb67ae85 3c6ef372 a54ff53a 510e527f 9b05688c 1f83d9ab 5be0cd19 
sha256 (finalize): 00 00 00 00 00 00 00 00 
out              : af af fe d8 5c db 5e dd bd 75 04 5a b1 54 ba 0c 04 eb 92 6c d2 6f 01 68 e8 fb d0 f4 a8 35 2a 43
# the out value above is incorrect

# the correct value is:
2e1d05c3a72fe13a1770451c103503be5ae1381282ea1ea1587180e512aae33f