Access violation when using OpenSSL's HMAC

I'm trying to do an HMAC-SHA512 on some data using OpenSSL. I get an "Exception thrown at 0x... (libcrypto-1_1-x64.dll) in Program.exe: 0xC0000005: Access violation writing location 0x..." error when executing the following code:

int main(int argc, char** argv)
{
  uint8_t* data[] = { 0x14, 0xf7, 0xbd, 0x95, 0x57, 0x9a, 0x7e, 0xa1, 0x5c, 0xf7, 0x27, 0x91, 0x0d, 0x61, 0x58, 0x01, 0xa3, 0x12, 0x17, 0x54, 0x0b, 0x2e, 0xb4, 0xc5, 0xb1, 0xeb, 0xab, 0xe0, 0x43, 0x9b, 0x8e, 0x1f, 0x39, 0x7d, 0x85, 0x1a, 0x3a, 0x4b, 0x9c, 0xf4, 0xbf, 0x31, 0x55, 0x72, 0x41, 0xf5, 0xdb, 0xcb, 0xb3, 0xa6, 0xb5, 0xb8, 0x82, 0xe5, 0xef, 0x18, 0x72, 0xa0, 0x59, 0x08, 0x9b, 0xfa, 0x17, 0xa3 };
  uint8_t* key = "some_rand_pw";
  uint8_t* result = malloc(64);
  memset(result, 0, 64);
  HMAC(EVP_sha512(), key, 12, data, 64, result, (unsigned int)64); //ERROR
}

I would use uint8_t* result = HMAC(EVP_sha512(), key, 12, data, 64, NULL, NULL), but it isn't thread safe, and this will be a multithreaded program. Anyone have any idea what I did wrong here?

I'm using Visual Studio 2017 with 64-bit OpenSSL pre-built for Windows.

Your code is wrong. data must be an array of uint8, but you declared it as an array of pointers to uint8.

Furthermore the last parameter of HMAC must be a pointer to unsigned int but you provided an unsigned int, that's the reason for the crash.

Your compiler should have warned you. Compile with -Wall.

Corrected (untested) code:

int main(int argc, char** argv)
{
  uint8_t data[] = { 0x14, 0xf7, 0xbd, 0x95, 0x57, 0x9a, 0x7e, 0xa1, 0x5c, 0xf7, 0x27, 0x91, 0x0d, 0x61, 0x58, 0x01, 0xa3, 0x12, 0x17, 0x54, 0x0b, 0x2e, 0xb4, 0xc5, 0xb1, 0xeb, 0xab, 0xe0, 0x43, 0x9b, 0x8e, 0x1f, 0x39, 0x7d, 0x85, 0x1a, 0x3a, 0x4b, 0x9c, 0xf4, 0xbf, 0x31, 0x55, 0x72, 0x41, 0xf5, 0xdb, 0xcb, 0xb3, 0xa6, 0xb5, 0xb8, 0x82, 0xe5, 0xef, 0x18, 0x72, 0xa0, 0x59, 0x08, 0x9b, 0xfa, 0x17, 0xa3 };
  uint8_t* key = "some_rand_pw";
  uint8_t* result = malloc(64);
  unsigned int len;
  memset(result, 0, 64);
  HMAC(EVP_sha512(), key, 12, data, 64, result, &len);
}

There is still room for improvement though.