Does #include affect program size?

Question

When my cpp file uses #include to add some header, does my final program\'s size gets bigger? Header aren\'t considered as compilation units, but the content of

Answer 1

For headers that are entirely declarative (as they generally should be), no. However the pre-processor and compiler have to take time to parse the headers, so headers can increase compile time; especially large and deeply nested ones such as - which is why some compilers use 'precompiled headers'.

Even inline and template code does not increase code size directly. If the template is never instantiated or an inline function not called, the code will not be generated. However if it is called/instantiated, code size can grow rapidly. If the compiler actually inlines the code (a compiler is not obliged to do so, and most don't unless forced to), the code duplication may be significant. Even if it is not truly inlined by the compiler, it is still instantiated statically in every object module that references it - it takes a smart linker to remove duplicates, and that is not a given - if separate object files were compiled with different options, inline code from the same source may not generate identical code in each object file, so would not even be duplicated. In the case of templates, and separate instantiation will be created for each type in is invoked for.