[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Error reporting should be improved

From: Bob Friesenhahn
Subject: Re: Error reporting should be improved
Date: Tue, 29 Dec 2009 18:25:34 -0600 (CST)
User-agent: Alpine 2.01 (GSO 1266 2009-07-14)

This note in the Solaris manual page for dlerror() is interesting:

     The messages returned by  dlerror() can reside in  a  static
     buffer that is overwritten on each call to dlerror(). Appli-
     cation code should not write to this buffer.  Programs want-
     ing  to  preserve  an  error  message  should make their own
     copies of that message.

The implementation of lt__set_last_error  is:

  static const char       *last_error     = 0;
  const char *
  lt__set_last_error (const char *errormsg)
    return last_error = errormsg;

so the current implementation is not reliable since the buffer pointed to may be updated several times before it is used. It is also not thread safe. Note that dlerror() may only be invoked once per error since calling it a second time returns a null pointer. The Linux manual page recommends invoking dlerror() to clear any existing error message before invoking dlsym() (which we are not doing) so a symbol which has a valid value of zero will result in picking up some old error message.

It is not clear how to make the interface completely thread safe, but it is clear that the message needs to be copied immediately to a private buffer before returning back to the caller in order to make sure that the error returned is due to invoking a libltdl function.

Bob Friesenhahn
address@hidden, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/

reply via email to

[Prev in Thread] Current Thread [Next in Thread]