Which .h files are included implicitly during compilation with cl.exe ?

Question

Why this compiles, when I don't include any .h file with size_t definition ?

int main () {  
  size_t volatile a{ 1 };  
  return 0;  
}  

The compilation command is simply "cl.exe filename.cpp" without any parameters.

Answer 1

Take a look at the following SO link -- https://stackoverflow.com/questions/48234476/c-size-t-doesnt-need-cstddef-header

I think what you are seeing is behavior exhibited by the VC++ compiler, not the implicit inclusion of header files. If I open a standard command prompt window and run cl.exe without setting any of the usual environment variables set by a Developer Command Prompt (include file, library paths, etc.) your code will still compile although it will not link.