01-29-2013
John,
I was confused especially after reading the MAN page itself that mentioned of memory location for “unknown error numbers” (which I referred above) but didn’t talk of the memory location of the address returned by this function under normal circumstances.
The primary reason to ask this query is because of the fact that the MAN pages themselves not making me sure if the programmer needs to handle any kind of cleanup post calling strerror()? Just like the call to stat(), lstat(), fstat() which create objects of type struct stat on the heap itself (whose address is returned through the pointer struct stat *sb) and puts the onus of the cleanup on the programmer only.
Available examples too didn’t give the clarity as they all called the function strerror() and used the address returned into their processing and were of just few lines only. Hence I was not getting sure of the error handling aspect of those few liner examples (sometimes they might just overlook error handling part just to give us the feel of the function).
The code I was working was critical enough not to have scope for silly errors. Hence couldn’t have overlooked the cleanup part if the allocation happens to be on the heap and couldn’t have just called to free the address either if it belonged to a different memory region.
Hope you got the dilemma making me to forward this query to the forum.
Last edited by Praveen_218; 01-29-2013 at 02:28 AM..
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PERROR(3) Library Functions Manual PERROR(3)
NAME
perror, strerror - system error messages
SYNOPSIS
perror(s)
char *s;
#include <string.h>
char *
strerror(errnum)
int errnum;
DESCRIPTION
The strerror() and perror() functions look up the error message string corresponding to an error number.
The strerror() function accepts an error number argument errnum and returns a pointer to the corresponding message string.
The perror() function finds the error message corresponding to the current value of the global variable errno (intro(2)) and writes it,
followed by a newline, to the standard error file descriptor. If the argument string is non-NULL, it is prepended to the message string
and separated from it by a colon and space (`: '). If string is NULL, only the error message string is printed.
If errnum is not a recognized error number, the error message string will contain ``Unknown error: '' followed by the error number in deci-
mal.
The error messages are stored in a data file now rather than an in memory array. See syserror(5).
SEE ALSO
mkerrlst(1), intro(2), psignal(3), strerror(3), syserror(3), syserror(5)
BUGS
The strerror() function returns its result in a static buffer which may be overwritten by subsequent calls.
The array sys_errlist[] and the global sys_nerr are obsolete and should not be used. They have, for the time being, been placed in an
object library liberrlst.a.
4th Berkeley Distribution March 21, 1996 PERROR(3)