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Diffstat (limited to 'system/doc/reference_manual/code_loading.xml')
| -rw-r--r-- | system/doc/reference_manual/code_loading.xml | 34 |
1 files changed, 23 insertions, 11 deletions
diff --git a/system/doc/reference_manual/code_loading.xml b/system/doc/reference_manual/code_loading.xml index 0e148298b1..f56e1ff408 100644 --- a/system/doc/reference_manual/code_loading.xml +++ b/system/doc/reference_manual/code_loading.xml @@ -121,8 +121,10 @@ loop() -> <title>Running a function when a module is loaded</title> <warning> - <p>This section describes an experimental feature introduced in R13B03. - There may be backward-incompatible changes in the feature in future releases.</p> + <p>This section describes an experimental feature that was + introduced in R13B03, and changed in a backwards-incompatible + way in R13B04. There may be more backward-incompatible changes + in future releases.</p> </warning> <p>The <c>-on_load()</c> directive names a function that should @@ -133,25 +135,35 @@ loop() -> <p>It is not necessary to export the function. It will be called in a freshly spawned process (which will be terminated as soon as the function - returns). The function must return <c>true</c> if the module is to - be remained loaded and be callable, or <c>false</c> if the module - is to be unloaded. Returning any other value or generating an exception - will also cause the module to be unloaded.</p> + returns). The function must return <c>ok</c> if the module is to + be remained loaded and become callable, or any other value if the module + is to be unloaded. Generating an exception will also cause the + module to be unloaded. If the return value is not an atom, + a warning error report will be sent to the error logger.</p> <p>A process that calls any function in a module whose <c>on_load</c> function has not yet returned will be suspended until the <c>on_load</c> function has returned.</p> + <p>In embedded mode, all modules will be loaded first and then + will all on_load functions be called. The system will be + terminated unless all of the on_load functions return + <c>ok</c></p>. + <p>Example:</p> <pre> -module(m). --on_load(run_me/0). +-on_load(load_my_nifs/0). + +load_my_nifs() -> + NifPath = ..., %Set up the path to the NIF library. + Info = ..., %Initialize the Info term + erlang:load_nif(NifPath, Info).</pre> -run_me() -> - %% Do something with side effects here, for instance load a library - %% containing native-implemented functions. - true.</pre> + <p>If the call to <c>erlang:load_nif/2</c> fails, the module + will be unloaded and there will be warning report sent to + the error loader.</p> </section> |