Question

Is there a way to write a qt library such that I can then use it (statically linked is fine) in a C application?
My C code is huge, old and will not convert to C++ without an inordinate amount of work. I say this as other similar questions seem to answer “just make your C code a Qt app”. That’s not an option.
I hope I can write a qt library, and build it in a way that lets it be called from C (something alluded to in QLibrary documentation).

The symbol must be exported as a C
function from the library for
resolve() to work. This means that the
function must be wrapped in an extern
“C” block if the library is compiled
with a C++ compiler. On Windows, this
also requires the use of a dllexport
macro; see resolve() for the details
of how this is done.

Can someone confirm/deny that I can do this, and let me know how much “qt” I can put in the library?
I don’t need a GUI but would like to use some of the SQL handling.

Cheers

Mike

Answer 1

You can put as much Qt in a library as you wish, including full UI capability. The rub is that since you want to access it from C code, you must provide your own access functions and your C functionality will be constrained to whatever level of access you provide.

You can even pass Qt object pointers between C and C++ but you’ll need to cast them into something that C can compile — either void * or preferably your own new type definition (such as C_QString *). To C code these pointers will be opaque, but they’ll still be valid.