Programming

I am new to Linux system programming, and I found the sophisiticated definition of some library function differ a lot with what I learnt in classes.

Here is the question:
what does the suffix of function `chmod' in sys/stat.h mean. The funtion claimation is like following:

Code:

    extern int chmod (__const char *__file, __mode_t __mode)
     __THROW __nonnull ((1));

According to my broken programming knowledge, suffix like "__THROW __nonnull ((1))" appear only in the C++, and they are generally used to handle the throwing of exceptions inside the functions.

I am glad anybody who is willing to share his/her idea. Thanks a lot.

Hi,

those functions qualifiers are simply compiler directives to tell gcc: this function does not throw any exception, and the first pointer must be non NULL. With this information, the compiler can better optimize the code around the call to chmod(), especially if you're calling chmod() from a C++ code.

These macro can be found in /usr/include/sys/cdefs.h by the way.

HTH,
Loïc.

gcc has lots of nonstandard extensions like that. Some assist the programmer by providing warnings or errors for things the compiler wouldn't otherwise be able to catch. I've had gcc warn me that I called printf with an incorrect number of arguments, an error message of quite surprising intelligence.

But I think not only the gcc does, because the busybox source package can also be compiled using the windows vs2005 (which has the support for GNU makefile), so may be the ANSI C has already added the support for more functionality (including the exceptional handling mechanism). (I guess)

C++ exceptions remain C++.

Being compiled under Visual Studio 2005 would mean using the Visual Studio headers and not the glibc ones, would it not?

My god, I forgot that all the C codes under vs2005 are compiled using the same compiler shared by the C++'s. Thanks for reminding.