extern int ioctl (int __fd, unsigned long int __request, ...) __THROW;
how does one read above?
I was thinking global int type function name ioctl has these (....).. but what is
__THROW mean???
btw, where is best resource to understand headers??
thanks in advance~
__THROW can mean anything. It is not defined by the standard
I'm not really sure what you mean by "understand headers" but if you're trying to understand <stdio.h> then I truly wish you the best of luck.This is a system-specific issue, and does not apply to C.
For reference, __THROW is meant to declare the function as capable of
throwing exceptions (a C++ feature). In C, the macro does nothing.
Well given that it's written in UPPERCASE with leading underscores, it's probably defined as a macro by some other header file.
In particular, it might be defined as nothing at all for C, and the usual 'throw' for C++.
Then again, it might not be - you would have to find the actual macros in your header files.
If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
If at first you don't succeed, try writing your phone number on the exam paper.
that's what i don't understand.
I have gone through other included headers and did not see the __THROW defined anywhere.
Code:#ifndef _SYS_IOCTL_H #define _SYS_IOCTL_H 1 #include <features.h> __BEGIN_DECLS /* Get the list of `ioctl' requests and related constants. */ #include <bits/ioctls.h> /* Define some types used by `ioctl' requests. */ #include <bits/ioctl-types.h> /* On a Unix system, the system <sys/ioctl.h> probably defines some of the symbols we define in <sys/ttydefaults.h> (usually with the same values). The code to generate <bits/ioctls.h> has omitted these symbols to avoid the conflict, but a Unix program expects <sys/ioctl.h> to define them, so we must include <sys/ttydefaults.h> here. */ #include <sys/ttydefaults.h> /* Perform the I/O control operation specified by REQUEST on FD. One argument may follow; its presence and type depend on REQUEST. Return value depends on REQUEST. Usually -1 indicates error. */ extern int ioctl (int __fd, unsigned long int __request, ...) __THROW;
Last edited by Salem; 03-22-2010 at 12:42 PM. Reason: [code] tags have [ ], not <>
If it is not intended for external use you may not find it declared in a header, you may need to examine the entire source (if available). Kind of irritating, but I have seen this before.Originally Posted by convenientstore
C programming resources:
GNU C Function and Macro Index -- glibc reference manual
The C Book -- nice online learner guide
Current ISO draft standard
CCAN -- new CPAN like open source library repository
3 (different) GNU debugger tutorials: #1 -- #2 -- #3
cpwiki -- our wiki on sourceforge
It seems to be defined on several places. One of them is sys/cdefs.h for me. How it is actually defined depends on some conditions. Here's part of the headerfile that is used for GCC:
It seems to specify for C++ that the function won't throw anything, if supported. If not supported, it won't mean anything.Code:# if !defined __cplusplus && __GNUC_PREREQ (3, 3) # define __THROW __attribute__ ((__nothrow__)) # define __NTH(fct) __attribute__ ((__nothrow__)) fct # else # if defined __cplusplus && __GNUC_PREREQ (2,8) # define __THROW throw () # define __NTH(fct) fct throw () # else # define __THROW # define __NTH(fct) fct # endif # endif
