How to interface with C++ code or dll?

[Suliman via Digitalmars-d-learn]

I am trying to understand how to use C++ lib from D.
For my App I need http://www.gdal.org

I had read about using C++ libs from D, and understood that there 
is 2 ways:
1. Make binding - convert .H to .d (I still do not fully 
understand what is it)
2. Use directly C++ lib (.dll)

I decided to start from simple example 
http://www.gdal.org/warptut.html

For compiling it's need #include "gdalwarper.h", so I maked 
gdalwarper.d with tool htod.
I know that it's not recommended for usage more, but other tools 
look too complex for me (I even do not understand how to sun them 
on Windows).

After I had add import gdalwarper.d to my test project. But 
during compilation it's asked me about other d files, that I 
included one ny other in App.d file. In the result I got error 
that:
"source\cpl_port.d(147): Error: module ctype is in file 
'std\c\ctype.d' which can not be read"

I have got a question. Files that I include is only header files. 
They do not include any code. How App would run? I should specify 
C++ source location or what?

=========

Then I decided to look how to use ready dll. As far as I know D 
have directive pragma(), that allow to import any lib.
Also afaik that it support inly import of dll in format of lib. 
Am I right?

And next. How I can understand which lib do I need. All 
documentation of GDAL assume that programmer will use source 
code, but not libs. And what I should to do? I download gdal 
bins, and there is a lot of dlls and I even can't understand 
which of them I need.