How to create a weak function in Cx51

"I don't follow what you're saying there - but I don't think what you're describing would be covered by "weak" functions anyhow?"

The project of the company I work in. There is a kernel in the project and the kernel would need to call a function to the user to indicate that there is an event happens.

If the user needs to handle the event, then it needs to port the code in the function. otherwise, the user doesn't need to handle the event. they could do nothing about the function.

That is why I want to use the weak function. I can create the function which it calls to the user as a weak function to do default handling. The user can choose the behavior of the function is default or they want to do more.

"I don't follow what you're saying there - but I don't think what you're describing would be covered by "weak" functions anyhow?"

The project of the company I work in. There is a kernel in the project and the kernel would need to call a function to the user to indicate that there is an event happens.

If the user needs to handle the event, then it needs to port the code in the function. otherwise, the user doesn't need to handle the event. they could do nothing about the function.

That is why I want to use the weak function. I can create the function which it calls to the user as a weak function to do default handling. The user can choose the behavior of the function is default or they want to do more.

So implementing a callback mechanism would be a possible solution.

"If the user needs to handle the event, then it needs to port the code in the function. otherwise, the user doesn't need to handle the event. they could do nothing about the function."

Then having the default handler in a library (a true, pre-built, binary) would solve that - the linker will only take the function from the library if it isn't provided by the user.

Providing it as source would also work - the user only has to touch the "default" source when they want to do specific handling.
This is what you'd have to do anyhow with a "WEAK" attribute.

A callback would also be possible but, as already noted, function pointers are problematic in C51.

Then having the default handler in a library (a true, pre-built, binary) would solve that - the linker will only take the function from the library if it isn't provided by the user.

How about C++ on a C51 :-)

Filip Natronce would be the man to ask about that

http://www.keil.com/forum/10074/

"Then having the default handler in a library (a true, pre-built, binary) would solve that - the linker will only take the function from the library if it isn't provided by the user."

Yes, I just want to create a library-like kernel. Then providing a function description like putchar() for users that can modify it if they want to. If users want to use the kernel I make, they just include the head file then they can use the function about the kernel. Because some kind of function in the kernel is necessary for the application. So the user couldn't allow renaming that functions. But if they want to do more things. They can create the function with the same function names, then modify it.