01-25-2008
How does NORET_TYPE works ?
Hi,
I was looking at the panic() code in linux kernel which is defined as:
51 /**
52 * panic - halt the system
53 * @fmt: The text string to print
54 *
55 * Display a message, then perform cleanups.
56 *
57 * This function never returns.
58 */
59
60 NORET_TYPE void panic(const char * fmt, ...)
where, NORET_TYPE is declared as
/*
753 * Ok, these declarations are also in <linux/kernel.h> but none of the
754 * ext3 source programs needs to include it so they are duplicated here.
755 */
# define NORET_TYPE /**/ <====
Please help me in understanding a #defined variable(NORET_TYPE here) which is not defined to anything.
I know that panic() function was designed in this way to not to return anything{in case of panic,there won't be anyone to catch the return value from panic() },but how does this work.
i think a program in user land having a #defined variable which is left blank will throw compile time error.how this is implemented in linux kernel ?
I don't know much about C,hence please excuse me if this is a stupid querry .
~amit
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LEARN ABOUT FREEBSD
xo_message
LIBXO(3) BSD Library Functions Manual LIBXO(3)
NAME
xo_err -- emit errors and warnings in multiple formats
LIBRARY
library ``libxo''
SYNOPSIS
#include <libxo/xo.h>
void
xo_warn(const char *fmt, ...);
void
xo_warnx(const char *fmt, ...);
void
xo_warn_c(int code, const char *fmt, ...);
void
xo_warn_hc(xo_handle_t *xop, int code, const char *fmt, ...);
void
xo_err(int eval, const char *fmt, ...);
void
xo_errc(int eval, int code, const char *fmt, ...);
void
xo_errx(int eval, const char *fmt, ...);
void
xo_message(const char *fmt, ...);
void
xo_message_c(int code, const char *fmt, ...);
void
xo_message_hc(xo_handle_t *xop, int code, const char *fmt, ...);
void
xo_message_hcv(xo_handle_t *xop, int code, const char *fmt, va_list vap);
DESCRIPTION
Many programs make use of the standard library functions err(3) and warn(3) to generate errors and warnings for the user. libxo wants to
pass that information via the current output style, and provides compatible functions to allow this.
These functions display the program name, a colon, a formatted message based on the arguments, and then optionally a colon and an error mes-
sage associated with either errno or the code parameter.
EXAMPLE:
if (open(filename, O_RDONLY) < 0)
xo_err(1, "cannot open file '%s'", filename);
ADDITIONAL DOCUMENTATION
Complete documentation can be found on github:
http://juniper.github.io/libxo/libxo-manual.html
libxo lives on github as:
https://github.com/Juniper/libxo
The latest release of libxo is available at:
https://github.com/Juniper/libxo/releases
SEE ALSO
xo_emit(3)
HISTORY
The libxo library was added in FreeBSD 11.0.
AUTHOR
Phil Shafer
BSD
December 4, 2014 BSD