The Open Group Base Specifications Issue 7
IEEE Std 1003.1-2008, 2016 Edition
Copyright © 2001-2016 The IEEE and The Open Group

#### NAME

> dlerror - get diagnostic information

#### SYNOPSIS

> ``#include <dlfcn.h>
> char *dlerror(void);
> ``

#### DESCRIPTION

> 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.

#### RETURN VALUE

> 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 terminated.

#### ERRORS

> No errors are defined.

The following sections are informative.

#### EXAMPLES

> The following example prints out the last dynamic linking error:

>     ...
>     #include <dlfcn.h>

>     char *errstr;

>     errstr = dlerror();
>     if (errstr != NULL)
>         printf ("A dynamic linking error occurred: (%s)\n", errstr);
>     ...

#### APPLICATION USAGE

> 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.

#### RATIONALE

> None.

#### FUTURE DIRECTIONS

> None.

#### SEE ALSO

> dlclose, dlopen, dlsym

> XBD <dlfcn.h>

#### CHANGE HISTORY

> First released in Issue 5.

#### Issue 6

> A note indicating that this function need not be reentrant is added to the DESCRIPTION.

#### Issue 7

> Austin Group Interpretation 1003.1-2001 #156 is applied.

> The dlerror() function is moved from the XSI option to the Base.

> POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0070 [75], XSH/TC1-2008/0071 [97], and XSH/TC1-2008/0072 [133] are applied.

> POSIX.1-2008, Technical Corrigendum 2, XSH/TC2-2008/0082 [656] is applied.

End of informative text.

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