Linker error on using "CreateCompa...

[Dmitry Titov]

I have created the project. The project type is "Win32 DLL". There is the
following string in my project:
HDC hCDC = CreateCompatibleDC(hdc);
I see following error after compiling:
undefined reference to `CreateCompatibleDC@4'
But if i will create the project with type "Win32 GUI" and put this string
into it it will compiles without any errors. Why?

How can I compile my project with type "Win32 DLL"?
I am sorry if I have put my question to the wrong section.

[DARC]

I don't know much about windows or dll's. As for the error, you must define
the func CreateCompatibleDC() in your code or link with a library that defines
it. It may work with Win32 GUI because it loads with default files or paths to
those files. One of the default files has the definition of
CreateCompatileDC().

[Dmitry Titov]

How I can see, what files get linked automatically to a project?

[DARC]

A windows project is going to have a " #include <windows.h> " in your main
source file.
Inside of " windows.h " there will be different " #include " statements. Any
header file (.h) and or source file (.cpp) you add can include files too.
Basicly they will all be linked in your final program.
Your problem is that one of your header files(.h), source files(.cpp), or
libray files (lib*.a) does not have a definition for "CreateCompatibleDC()".
You need to link with the right library and or source file if DLL's work like
a special library built for windows applications.
If this is your own function make sure you: 1 declare it; 2. define it;
optional 3. declare and define it in same place; 4. add to your project (if a
source file) or source file (if a header file).
Happy Hunting

[Dmitry Titov]

The function declaration “CreateCompatibleDC” is in a file “wingdi.h”. This
file is connected to the project as follows: “Tools-> CompilerOption->
Directories-> CInclude” the path “C:\Dev-Cpp\include \is specified”. Here
there is a file “wingdi.h”. The function description “CreateCompatibleDC” in
library “libgdi32.a”. This library is to the address “C:\Dev-Cpp\lib \”. It is
the address it is specified in compiler customisations: “Tools->
CompilerOption-> Directories-> Libraries”.
Specified above customisation are identical to both projects, but for the type
project “WIN32 DLL” the compiler produces an error. For the type project
“WIN32 GUI” compilation passes successfully.
In a directory with the type project “WIN32 DLL” I have copied a file
“libgdi32.a”. Also has made following customisations: “Project->
ProjectOptions-> Parameters-> Linker” has entered a filename “libgdi32.a”.
Compilation has passed successfully.
Why? After all the file “libgdi32.a” should be connected to the project
without additional customisations?

[DARC]

Good job. How did you find the definition in that library??
By the way the solution was
"Project->ProjectOptions->Parameters->Linker\libgdi32.a". The library was in
the search path (you stated) so the linker parameter was the answer.
Libgdi32.a is somehow not default in DLL projects, but it is default in WIN
gui project.
I wonder if it would have worked if you had added the libgdi32.a as a project
file, but had left out the linker parameter? You know just like adding source
files to a library project. I haven't created no DLLs and only a few basic
librarys from book examples. Anyways, good job and get back with how you found
the definition in that library

[Dmitry Titov]

I know "CreateCompatibleDC" is GDI function. The only library contains letters
"gdi" at its name is libgdi32.a. I have connected this library and everything
works.
But i can't understand why this library must be connected especially?

[Dmitry Titov]

There are also special utilities to view functions contained in dynamic or
static libraries.

[DARC]

Have you used "C++filter.exe"? I cant seem to make it work. It echos back my
parameter only. I resently got this old exacutable called "nm.exe" from the
DJGPP suite of C++ . I had to make a batch program to filter out all the info
it provides. "C++filter.exe" is newer, but it doesn't give any data at all.
Does it store it to a file?? I have many library files from Quincy2002 suite,
Dev-C++ suite, and recently the DJGPP suite but you cant open them to see what
they contain. The header files usually look cryptic and look like they contain
either C or weird macro constructs. I only use what the book I am currently
reading dictates. That usually is a small hand full of headers and what ever
default library the IDE is set up to compile with. Any help with learning more
about all the headers and librarys is appreciated.
Sorry about the last question you posted, I don't think I understand what your
asking.

[laxman varada]

hi,
As for the error, you must define the func CreateCompatibleDC() in your code
or link with a library that defines it. It may work with Win32 GUI because it
loads with default files or paths to those files. One of the default files has
the definition of CreateCompatileDC().

regards,
phe9oxis,
http://www.guidebuddha.com