dlerror

dlerror is a function in the dynamic linking facilities of Unix-like systems. It provides a human-readable description of the most recent error reported by the dynamic linker when using dlopen, dlsym, or dlclose. The function is declared in the header dlfcn.h and is part of the standard dynamic linker interface on POSIX-compliant platforms. The returned message is intended for debugging and logging.

dlerror returns a pointer to a null-terminated string describing the last error. The string is kept per-thread, and it should not be freed or modified by the program. Importantly, dlerror only remains valid until the next call to dlerror. A common usage pattern is to clear any existing error by calling dlerror() before calling dlopen or dlsym, then perform the operation, and immediately call dlerror() again to retrieve the error message if one occurred.

If there is no error, the returned pointer is NULL. If an error occurred, the returned pointer points to a human-readable message, such as indicating that a library could not be loaded or that a symbol could not be found. The exact text is implementation-dependent but typically describes the failure cause.

The error state is thread-local, allowing concurrent threads to report separate messages. The message is not guaranteed to remain stable across subsequent calls to dlerror; if you need to retain it, copy it promptly.

dlerror is available on most Unix-like systems, including Linux, macOS, and BSD variants. It is not part of the Windows API, which uses a different dynamic loading mechanism.