VC++ resources in a static library

StackOverflow https://stackoverflow.com/questions/531502

Question

Is it possible to build resources into a static library and reuse them by simply linking with the library?

I'm primarily thinking about the case where you call a function in the library which in turn accesses resources.

Was it helpful?

Solution

It can be done, but it's quite painful: You can't do it by simply linking with the static library.

Consider this: resources are embedded in an EXE or DLL. When some code in the static library calls (e.g.) LoadIcon, it'll get the resources from the EXE or DLL that it's linked with.

So, if your static library requires resources to be available, you've got a couple of options:

  1. You can have the library build them on the fly, and then use (e.g.) CreateDialogIndirect. See Raymond Chen's "Building a dialog template at run-time".
  2. You can have them embedded in the library as simple arrays (i.e.) char my_dialog_resource[] = { .... };, and then use (e.g.) CreateDialogIndirect. You'll probably need to find (or write) a utility that converts from .RES files to .CPP files.
  3. You can ship the LIB file with a resource script (.RC file) and corresponding header file. You then #include them as relevant. You'll need to reserve a range of resource IDs for the LIB to use, so that they don't collide with those of the main EXE or DLL. This is what MFC does when used as a static library. Or you can use string resource IDs (this doesn't work for STRINGTABLE resources).
  4. Your static library can ship with a separate resource DLL.

OTHER TIPS

The only thing you need to do to use resources (images, dialogs, etc...) in a static library in Visual C++ (2008), is include the static library's associated .res file in your project. This can be done at "Project settings/Linker/Input/Additional dependencies".

With this solution, the resources of the static library are packed into the .exe, so you don't need an extra DLL. Regrettably, Visual Studio does not include the .res file automatically as it does for the .lib file (when using the "project dependencies"-feature), but I think this small extra step is acceptable.

I have looked for a very long time for this solution, and now it surprises me it is that simple. The only problem is that it is totally undocumented.

I just went through this with the MS Visual Studio compiler. We were converting some legacy projects from DLLs into static libraries. Several of these DLLs had dialog or string resources embedded in them. I was able to compile the .RC scripts for these DLLs into our main application by including them in the main application's RC script file via the "TEXTINCLUDE" mechanism. I found it easiest to do this by editing the RC file directly, but Visual Studio provides a slightly more "wizardy" mechanism as well. The implementation is most likely different in other compilers.

To manipulate the main RC script directly:

.1. In the "2 TEXTINCLUDE" section, include the header file that defines the resource IDs for your library. The syntax is 

2 TEXTINCLUDE 
BEGIN
    "#include ""my_first_lib_header.h""\r\n"
    "#include ""my_second_lib_header.h""\0" 
END

.2. In the "3 TEXTINCLUDE" section, include the RC script from your library.

3 TEXTINCLUDE
BEGIN
    "#include ""my_first_library.rc""\r\n"
    "#include ""my_second_library.rc""\0"
END

Steps 3 and 4 should happen automatically, but I found it was more reliable to just enter them myself, rather than depending on Microsoft's resource script compiler to take care of things.

.3. Add the header file with your libraries resource defines to the read only symbols list. This list is usually near the top of the file.

#define APSTUDIO_READONLY_SYMBOLS
#include "my_first_lib_header.h"
#include "my_second_lib_header.h"
#undef APSTUDIO_READONLY_SYMBOLS

.4. Include your library's RC script in the APSTUDIO_INVOKED section. This is usually at the bottom of the file.

#ifndef APSTUDIO_INVOKED
#include "my_first_library.rc"
#include "my_second_library.rc"
#endif

You can also do all of this automatically through the visual studio IDE, but I found it didn't always apply when I expected it to.

  1. Open the "Resource View" window in Visual Studio.
  2. Right-click on your main application's resource file and choose "Resource Includes..." from the context menu.
  3. In the box labeled "Read-only symbol directives," add the include statements for the .h files that define the resource ID's for your libraries.
  4. In the box labeled "Compile-time directives," add the include statements for your library's .rc script.
  5. Click okay. You may also want to manually trigger the RC script compilation, to make sure it happens.

If your library's resource script references any files on disk (text files, icons files, etc.), you'll need to make sure that the main application project knows where to find them. You can either copy these files to somewhere your application can find them or you can add an additional include path in the compiler settings.

To add an additional include path:

  1. Open up the properties dialog for your main application.
  2. Select "Configuration Properties/Resources/General" from the left-hand navigation pane.
  3. In the properties list, Enter any pertinent paths next to "Additional Include Directories."

I don't think so. Static library doesn't have it's own HINSTANCE. It's code is executed in the context of DLL or EXE which links it. That's why all the resources you'll try to load from the static library's code will be of that enclosing DLL/EXE.

I did that kind of resources reuse with a DLL though, as far as it has it's own address space, and you can call LoadResource with DLL's HINSTANCE.

As per Visual Studio 2010, the development tools from Microsoft apparently cannot properly handle compiled resource data inside static libraries at all.

To distribute a compiled resource file (a .res file), you have two choices:

  1. Distribute the .res files separately, and instruct the client code to link against them;
  2. Use cvtres to merge several .res files into a single object (.obj) file, and provide it separately.

Note that you can't lib in object files created with cvtres. If multiple object files are provided, lib complains as though as multiple .res files were given; if a single object file is provided, lib does not complain, but the linker simply ignores the embedded resource data in the lib file.

It might be the case that there is a way to force the linker to read and link the libbed in resource data (with some command-line option, section manipulation and so on), since the resource data is indeed available in the library (as dumpbin reveals). So far, I haven't found a solution, and, unless one is willing to hack the development tools, anything better than this simple solution is probably not worth the effort.

The only way to ship resource data in a static library (in this case, with a static library) is to distribute the resources separately and explicitly link them in the client code. Using cvtres can reduce the number of distributed resource files to one, if you have many of them.

The recommended way is to provide a dll with the resources together with your library.

When the following method is used, any resource (in this example, an icon) can be used as an integral part of a static library and such library can be used by any type of application, including a console one (which doesn't have any resource segment whatsoever).

  1. Icon is converted to a static array of BYTE. bin2c can be used for that.

  2. Data is converted into a HICON handle. Here is how I have done that:

    HICON GetIcon()
{ 
   DWORD dwTmp;
   int offset;
   HANDLE hFile;
   HICON hIcon = NULL;
   offset = LookupIconIdFromDirectoryEx(s_byIconData, TRUE, 0, 0, LR_DEFAULTCOLOR);
   if (offset != 0)
   {
      hIcon = CreateIconFromResourceEx(s_byIconData + offset, 0, TRUE, 0x00030000, 0, 0, LR_DEFAULTCOLOR | LR_DEFAULTSIZE);
   }
   return hIcon;  
}

  3. GetIcon is used instead of LoadIcon. Instead of calling:

m_hIcon = ::LoadIcon(hInstanceIcon, MAKEINTRESOURCE(pXMB->nIcon));

Then call

m_hIcon = GetIcon()
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