Why does __func__ return in some functions in C?

Question

I have many different functions, and they all have simple `printf` statements using `__func__` similar to this one: `printf("%s - hello world!", __func__);` Now the problem I am running into is that in some functions it returns `<unknown>` instead of the function name. Why is that? Am I doing something wrong? AFAIK `__func__` is a part of `c99` so I don't understand why it isn't working as advertised. I am using GCC 4.7.2 in Debian.

Accepted Answer

It sounds like a header you are including must be doing something similar to this bug and defining `__func__` as follows:

```
define __func__ "<unknown>"
```

and so you only see it when you include that header(s). A quick way to test for this would be to use `__FUNCTION__` in a section of the code where `__func__` does not work. Then you need to narrow it down and figure out which header has the troublesome logic and fix it.

Why does func return <unknown> in some functions in C?

Solution

Problem

Why does __func__ return <unknown> in some functions in C?

Solution

Problem

Why does func return <unknown> in some functions in C?