erl_error
This module contains some error printing routines taken from "Advanced Programming in the UNIX Environment" by W. Richard Stevens.
These functions are all called in the same manner as
printf()
, that is, with a string containing format
specifiers followed by a list of corresponding arguments. All output from
these functions is to stderr
.
Functions
const char *FormatStr;
The message provided by the caller is printed. This
function is simply a wrapper for fprintf()
.
const char *FormatStr;
Use this function when a fatal error has occurred that
is not because of a system call. The message provided by the
caller is printed and the process terminates with exit
value 1
. This function does not return.
const char *FormatStr;
Use this function after a failed system call. The message provided by the caller is printed followed by a string describing the reason for failure.
const char *FormatStr;
Use this function after a failed system call. The message
provided by the caller is printed followed by a string
describing the reason for failure, and the process
terminates with exit value 1
. This function does not
return.
Error Reporting
Most functions in Erl_Interface
report failures to the caller by
returning some otherwise meaningless value (typically
NULL
or a negative number). As this only tells you that things did not
go well, examine the error code in erl_errno
if you
want to find out more about the failure.
Functions
erl_errno
is initially (at program startup) zero
and is then set by many Erl_Interface
functions on failure to
a non-zero error code to indicate what kind of error it
encountered. A successful function call can change
erl_errno
(by calling some other function that
fails), but no function does never set it to zero. This means
that you cannot use erl_errno
to see if a
function call failed. Instead, each function reports failure
in its own way (usually by returning a negative number or
NULL
), in which case you can examine
erl_errno
for details.
erl_errno
uses the error codes defined in your
system's <errno.h>
.
Note!
erl_errno
is a "modifiable lvalue" (just
like ISO C defines errno
to be) rather than a
variable. This means it can be implemented as a macro
(expanding to, for example, *_erl_errno()
).
For reasons of thread safety (or task safety), this is exactly what
we do on most platforms.