New way to Calculate SHA256Sum from OpenSSL v3

compute_sha256.c

#include <stdio.h>
#include <string.h>
#include <openssl/sha.h>
#include <openssl/evp.h>

#if OPENSSL_VERSION_NUMBER < 0x10100000L
#define EVP_MD_CTX_new EVP_MD_CTX_create
#define EVP_MD_CTX_free EVP_MD_CTX_destroy
#endif

char msg[] = "HashMe";

// Helper function to print the hash
void printHash(const char *hash) {
    for (int i = 0; i < SHA256_DIGEST_LENGTH; ++i) {
        printf("%02x", hash[i]);
    }

    printf("\n");
}

// This is the former way of calculating the hash, deprecated in OSSL3.x
void deprecatedHash() {
    unsigned char hash[SHA256_DIGEST_LENGTH] = {0,};

    SHA256_CTX myCtx;
    SHA256_Init(&myCtx);

    SHA256_Update(&myCtx, msg, strlen(msg));
    SHA256_Final(hash, &myCtx);

    printHash(hash);
}

// The preferred way from OSSL3.x+
void hash() {
    int sz = EVP_MD_size(EVP_sha256());
    unsigned char *hash = OPENSSL_malloc(sz);
    if (hash == NULL)
        return -1;

    EVP_MD_CTX *ctx;
    ctx = EVP_MD_CTX_new();
    if (ctx == NULL)
        return -1;

    // Error handling is not done here to keep the gist small and clean
    // All 3 functions below are expected to return 1 on successful operation
    EVP_DigestInit(ctx, EVP_sha256());
    EVP_DigestUpdate(ctx, msg, strlen(msg));
    EVP_DigestFinal(ctx, hash, &sz);

    printHash(hash);

    EVP_MD_CTX_free(ctx);
}