Thread: I'm converting a C++ project to C

The major issues are as follows:

structs/classes -
classes with functions not allowed in C so I have to pull them out and rename them/change parameters
no constructors or destructors
so I need init and destroy methods

new/delete -
all of these have to be replaced with malloc/free with corresponding init and destroy calls.

the use of booleans has to be corrected since there is none in C, but this is fixable with a simple typedef and find/replace.

the biggest problem is templates.

how the hell do I get rid of template data structures/classes elegantly. almost every solution that I can think of is beyond sloppy

Well realistically it appears that my only option is to go through the existing code, and find each type of item stored in a given template data structure and add each type to a union and use that as the data objects. Then I can add a bit field to the data structure to be set on initialization which would specify the type of data stored in an instance of the structure.

umm, well it's a library that needs to be integrated to work with some legacy code...

What you might want to do then is to create a set of wrapper functions. The template stuff might be a little difficult to do but should be possible. As long as the function signature is legal in C it really doesn't matter if the function body is C or C++.


edit: Bah I'm slow at posting today

Originally Posted by laserlight

Would it not be easier to convert the C code to work with the C++ library?

I would imagine so, but that's not mine to tamper with

Originally Posted by Thantos

What you might want to do then is to create a set of wrapper functions. The template stuff might be a little difficult to do but should be possible. As long as the function signature is legal in C it really doesn't matter if the function body is C or C++.


edit: Bah I'm slow at posting today

I think you are mistaken

Nope. If I have a function

Code:

int foo(int par1, char par2, double par3);

Then I can call it from a C program. In the body of foo I could go to town on all the C++ code I want. I simply compile the file with foo into an object file, compile the C program into object code and then link them together.

Originally Posted by Thantos

Nope. If I have a function

Code:

int foo(int par1, char par2, double par3);

Then I can call it from a C program. In the body of foo I could go to town on all the C++ code I want. I simply compile the file with foo into an object file, compile the C program into object code and then link them together.

I see what your intention is, however linking is something that requires overhead as well. I've essentially done something similar with managed C++ and C# and I ran into some issues that were not worth while.

Originally Posted by gotclout

I see what your intention is, however linking is something that requires overhead as well. I've essentially done something similar with managed C++ and C# and I ran into some issues that were not worth while.

Linking between two functions in different files require no more overhead then two functions in the same file. The calling method is the same.

To call C++ functions in C code you need to prefix your C++ functions with extern "C" so that the linkage will be compatible with C.

Code:

extern "C" int func(int something);