Visual Studio Intellisense finds function, but compiler doesnt [duplicate] - c++

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I am working with OpenSSL to try and get the SHA512 Hash function to work. When I am writing the code, Visual Studio's intellisense finds the function SHA512as well as all of the parameters that are included with it, but when I go to build the project, I get the error, "unresolved external symbol SHA512 referenced in function main." Here is what I have so far, it's based on a small example here.
stdafx.h
// stdafx.h : include file for standard system include files,
// or project specific include files that are used frequently, but
// are changed infrequently
//
#pragma once
#include "targetver.h"
#include <stdio.h>
#include <tchar.h>
#define _ATL_CSTRING_EXPLICIT_CONSTRUCTORS // some CString constructors will be explicit
#define _AFX_NO_MFC_CONTROLS_IN_DIALOGS // remove support for MFC controls in dialogs
#ifndef VC_EXTRALEAN
#define VC_EXTRALEAN // Exclude rarely-used stuff from Windows headers
#endif
#include <afx.h>
#include <afxwin.h> // MFC core and standard components
#include <afxext.h> // MFC extensions
#ifndef _AFX_NO_OLE_SUPPORT
#include <afxdtctl.h> // MFC support for Internet Explorer 4 Common Controls
#endif
#ifndef _AFX_NO_AFXCMN_SUPPORT
#include <afxcmn.h> // MFC support for Windows Common Controls
#endif // _AFX_NO_AFXCMN_SUPPORT
#include <iostream>
// TODO: reference additional headers your program requires here
#include <openssl/sha.h>
test.cpp
#include "stdafx.h"
#include <stdio.h>
#include <string.h>
int main() {
unsigned char digest[SHA512_DIGEST_LENGTH];
char string[] = "hello world";
SHA512((unsigned char*)&string, strlen(string), (unsigned char*)&digest);
char mdString[SHA512_DIGEST_LENGTH * 2 + 1];
for (int i = 0; i < SHA512_DIGEST_LENGTH; i++)
sprintf(&mdString[i * 2], "%02x", (unsigned int)digest[i]);
printf("SHA512 digest: %s\n", mdString);
return 0;
}
I have even checked and confirmed that SHA512 is in the sha.h file that is included in the stdafx.h file as well.