This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding Linux
manual page for details of Linux behavior), or the interface may not be
implemented on Linux.
dlerror — get diagnostic information
The dlerror() function shall return a null-terminated character string
(with no trailing <newline>) that describes the last error that occurred
during dynamic linking processing. If no dynamic linking errors have occurred
since the last invocation of dlerror(), dlerror() shall return
NULL. Thus, invoking dlerror() a second time, immediately following a
prior invocation, shall result in NULL being returned.
It is implementation-defined whether or not the dlerror()
function is thread-safe. A thread-safe implementation shall return only
errors that occur on the current thread.
If successful, dlerror() shall return a null-terminated character string;
otherwise, NULL shall be returned.
The application shall not modify the string returned. The returned
pointer might be invalidated or the string content might be overwritten by a
subsequent call to dlerror() in the same thread (if dlerror()
is thread-safe) or in any thread (if dlerror() is not thread-safe).
The returned pointer might also be invalidated if the calling thread is
No errors are defined.
The following sections are informative.
The following example prints out the last dynamic linking error:
Depending on the application environment with respect to asynchronous execution
events, such as signals or other asynchronous computation sharing the address
space, conforming applications should use a critical section to retrieve the
error pointer and buffer.
dlclose(), dlopen(), dlsym()
errstr = dlerror();
if (errstr != NULL)
printf ("A dynamic linking error occurred: (%s)\n", errstr);
The Base Definitions volume of POSIX.1‐2017,
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1-2017, Standard for Information Technology -- Portable Operating
System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018
Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html .
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