Cmake sqlite3 amalgamation

Question

I am not able to embedd the sqlite3 amalgamation in a simple cmake hello world executable. In a nutshell: test.h and test.cpp are just working, so why are sqlite.h and sqlite.c not? Also, using qmake (Qt's build system) it simply works, and I think the described steps are 100% the same.

main.cpp.obj:-1: error: LNK2019: unresolved external symbol sqlite3_open referenced in function main

Project dir

CMakeLists.txt
main.cpp
sqlite/
  |- sqlite3.c
  |- sqlite3.h
test/
  |- test.c
  |- test.h

CMakeLists.txt

cmake_minimum_required(VERSION 3.10)

project(sqlite_test LANGUAGES CXX)

set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
   
include_directories(${CMAKE_CURRENT_SOURCE_DIR}/sqlite ${CMAKE_CURRENT_SOURCE_DIR}/test)

add_executable(sqlite_test main.cpp sqlite/sqlite3.h sqlite/sqlite3.c test/test.h test/test.cpp)

qmake .pro file for comparison which just works

TEMPLATE = app
TARGET = sqlite_qmake

INCLUDEPATH += $$PWD/sqlite $$PWD/test

HEADERS += \
$$PWD/sqlite/sqlite3.h \
$$PWD/test/test.h

SOURCES += \
main.cpp \
$$PWD/sqlite/sqlite3.c \
$$PWD/test/test.cpp

test.h

#ifndef TEST_H
#define TEST_H

void sayhello();

#endif // TEST_H

test.cpp

#include "test.h"
#include <iostream>

void sayhello(){
    std::cout << "Hello Universe!" << std::endl;
}

main.cpp

#include <iostream>
#include "sqlite3.h"  
#include "test.h"

int main()
{
    cout << "Hello World!" << endl;
    sayhello();
    sqlite3 *db = nullptr;
    int rc = sqlite3_open("index.db", &db);
    if (rc != SQLITE_OK){
        return -1;
    }
    return 0;
}

Answer 1

That's because you have to explicitly say what languages you're going to work with. Just add C in the LANGUAGES list in the project command:

project(sqlite_test LANGUAGES CXX C)