Why / how are some c++ headers included by default in visual studio?

Question

In visual studio c++, some headers seems to be included by default. For example, I can use std::strncpy or std::string without including <string> or <cstring>, but I cannot use std::cout or std::min() without including <iostream> or <algorithm>.

Then, when I want to compile the source code on unix with g++, I get compilation error if I forgot to add the includes that visual studio did not warm me about because of its implicit includes.

Where does the default includes come from in visual studio? Is there a way to deactivate this behavior for future and existing projects? Note: my visual studio projects are not using precompiled headers.

Answer 1

Visual Studio has no headers included by default. However, some headers include other headers, so if you include <iostream>, that may sometimes include <string> in some compilers, and many headers also include <cstring>. So you are including them yourself, by accident.

Which headers includes which other headers varies from library to library, so always explicitly include the headers used by that file.