This module implements the ability to access symbols from shared libraries. On POSIX this uses the dlsym mechanism, on Windows LoadLibrary.

Examples

Loading a simple C function

The following example demonstrates loading a function called greet from a library that is determined at runtime based upon a language choice. If the library fails to load or the function greet is not found, it quits with a failure error code.

Example:

import std/dynlib
type
  GreetFunction = proc (): cstring {.gcsafe, stdcall.}

proc loadGreet(lang: string) =
  let lib =
    case lang
    of "french":
      loadLib("french.dll")
    else:
      loadLib("english.dll")
  assert lib != nil, "Error loading library"

  let greet = cast[GreetFunction](lib.symAddr("greet"))
  assert greet != nil, "Error loading 'greet' function from library"

  echo greet()

  unloadLib(lib)

Imports

strutils, posix

Types

LibHandle = pointer: A handle to a dynamically loaded library. Source Edit

Procs

proc checkedSymAddr(lib: LibHandle; name: cstring): pointer {. ...raises: [Exception, LibraryError], tags: [RootEffect].}: Retrieves the address of a procedure/variable from lib. Raises LibraryError if the symbol could not be found. Source Edit
proc libCandidates(s: string; dest: var seq[string]) {....raises: [], tags: [].}: Given a library name pattern s, write possible library names to dest. Source Edit
proc loadLib(): LibHandle {....gcsafe, raises: [], tags: [].}: Gets the handle from the current executable. Returns nil if the library could not be loaded. Source Edit
proc loadLib(path: string; globalSymbols = false): LibHandle {....gcsafe, raises: [], tags: [].}: Loads a library from path. Returns nil if the library could not be loaded. Source Edit
proc loadLibPattern(pattern: string; globalSymbols = false): LibHandle {. ...raises: [Exception], tags: [RootEffect].}: Loads a library with name matching pattern, similar to what the dynlib pragma does. Returns nil if the library could not be loaded.
Warning: this proc uses the GC and so cannot be used to load the GC.
Source Edit
proc raiseInvalidLibrary(name: cstring) {.noinline, noreturn, ...raises: [LibraryError], tags: [].}: Raises a LibraryError exception. Source Edit
proc symAddr(lib: LibHandle; name: cstring): pointer {....gcsafe, raises: [], tags: [].}: Retrieves the address of a procedure/variable from lib. Returns nil if the symbol could not be found. Source Edit
proc unloadLib(lib: LibHandle) {....gcsafe, raises: [], tags: [].}: Unloads the library lib. Source Edit