Input and Output files#
For any given input file, the file name suffix determines what kind of compilation is done. The following kinds of input file names are supported:
- file.d
- D source files. 
- file.dd
- Ddoc source files. 
- file.di
- D interface files. 
You can specify more than one input file on the gdc command line,
each being compiled separately in the compilation process.  If you specify a
-o file option, all the input files are compiled together,
producing a single output file, named file.  This is allowed even
when using -S or -c.
A D interface file contains only what an import of the module needs,
rather than the whole implementation of that module.  They can be created
by gdc from a D source file by using the -H option.
When the compiler resolves an import declaration, it searches for matching
.di files first, then for .d.
A Ddoc source file contains code in the D macro processor language.  It is
primarily designed for use in producing user documentation from embedded
comments, with a slight affinity towards HTML generation.  If a .d
source file starts with the string Ddoc then it is treated as general
purpose documentation, not as a D source file.