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Full Discussion: errno
Top Forums Programming errno Post 302242735 by redoubtable on Thursday 2nd of October 2008 04:39:25 PM
Old 10-02-2008
Quote:
Originally Posted by otheus
If stat() returns -1, THEN errno will be meaningful. Some implementations of libraries don't reset errno unless there actually was an error, meaning you might get the 'leftover' error of a previous call.
This is a very important observation for the original poster. The errno variable may not be accurate if there are more functions being called after the error occurred.

Code:
function1(); // let's says this function fails with EPERM errno will be 1
function2(); // this function also fails with ERANGE errno will be 34
/* errno was changed twice, so if you would analyze it here not knowing function2() had failed, you might consider an error which didn't belong to function1() */
function3(); // ...

 

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Tcl_SetErrno(3) 					      Tcl Library Procedures						   Tcl_SetErrno(3)

__________________________________________________________________________________________________________________________________________________

NAME
Tcl_SetErrno, Tcl_GetErrno, Tcl_ErrnoId, Tcl_ErrnoMsg - manipulate errno to store and retrieve error codes SYNOPSIS
#include <tcl.h> void Tcl_SetErrno(errorCode) int Tcl_GetErrno() const char * Tcl_ErrnoId() const char * Tcl_ErrnoMsg(errorCode) ARGUMENTS
int errorCode (in) A POSIX error code such as ENOENT. _________________________________________________________________ DESCRIPTION
Tcl_SetErrno and Tcl_GetErrno provide portable access to the errno variable, which is used to record a POSIX error code after system calls and other operations such as Tcl_Gets. These procedures are necessary because global variable accesses cannot be made across module bound- aries on some platforms. Tcl_SetErrno sets the errno variable to the value of the errorCode argument C procedures that wish to return error information to their callers via errno should call Tcl_SetErrno rather than setting errno directly. Tcl_GetErrno returns the current value of errno. Procedures wishing to access errno should call this procedure instead of accessing errno directly. Tcl_ErrnoId and Tcl_ErrnoMsg return string representations of errno values. Tcl_ErrnoId returns a machine-readable textual identifier such as "EACCES" that corresponds to the current value of errno. Tcl_ErrnoMsg returns a human-readable string such as "permission denied" that corresponds to the value of its errorCode argument. The errorCode argument is typically the value returned by Tcl_GetErrno. The strings returned by these functions are statically allocated and the caller must not free or modify them. KEYWORDS
errno, error code, global variables Tcl 8.3 Tcl_SetErrno(3)
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