Working with DLL in a C++ application

Question

I'm planning to use id3lib in my application. I'm looking for a way to use the library as a DLL. I've noticed that they released the library in various form: one of which is windows binary. My target platform in Windows, and I'll use Qt 4.8. After I extract the files in windows binary, I found the following files in Release folder:

id3lib.dll
id3lib.exp
id3lib.lib

I know how to use a DLL in Qt given the DLL, one or more header files where function prototypes resides, and with or without the *.lib file. This package doesn't come with a header file.

How am I supposed to use this package without any header file? What's the purpose of the *.lib and *.exp files here? As far as I know *.lib files are used for static linking with functions which I don't want in my program.

Your question is Windows specific and should be tagged as such. — Basile Starynkevitch, Mar 19 '12 at 06:52

score 2 · Answer 1 · answered Mar 19 '12 at 06:57

2

You've just missed the header. It is available under the include subfolder (see here), also the .lib file is still needed for linking, even if you'll be using the DLL.

answered Mar 19 '12 at 06:57

Robert

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I've the complete source code of id3lib. the windows binary section doesn't come with any header file. how do i know which header file should i use? – Donotalo Mar 19 '12 at 07:08
@Donotalo: follow the link in Robert's answer. It takes you straight to id3.h. – Harry Johnston Mar 19 '12 at 18:22
@HarryJohnston: id3.h is not the file to include. it is tag.h described here: http://id3lib.sourceforge.net/api/index.html. however, i tried both of them but still couldn't resolve some unreferenced link. – Donotalo Mar 20 '12 at 04:31
@Donotalo: are you getting an error from the compiler or from the linker? What functions/symbols are undefined? – Harry Johnston Mar 20 '12 at 20:26
@HarryJohnston: that's another question: http://stackoverflow.com/questions/9786022/undefined-reference-linker-error-while-using-id3lib-library-in-a-c-application – Donotalo Mar 21 '12 at 04:42

score 1 · Accepted Answer · answered Mar 19 '12 at 06:58

The usual course is to use a header file #included in the C++ file, the .lib file to link to and the .dll is required at run time.

The header file should/may be in another package as the same header is probably used for different kinds of linking strategies.

At worst you should be able to use a tool such as depends.exe to view the exported symbols and create your own h file to match - but it would be better to find a .h file issued with the release.

Working with DLL in a C++ application

2 Answers2