int(3)

NAME
int - Interpreter Interface.

DESCRIPTION

The Erlang interpreter provides mechanisms for breakpoints and stepwise execution of code. It is primarily intended to be used by Debugger; see the Users's Guide for Debugger and module debugger.

The following can be done from the shell:

    • Specify the modules to be interpreted.

    • Specify breakpoints.

    • Monitor the current status of all processes executing code in interpreted modules, also processes at other Erlang nodes.

By attaching to a process executing interpreted code, it is possible to examine variable bindings and order stepwise execution. This is done by sending and receiving information to/from the process through a third process, called the meta process. You can implement your own attached process. See int.erl for available functions and dbg_wx_trace.erl for possible messages.

The interpreter depends on the Kernel, STDLIB, and WX applications. This means that modules belonging to any of these applications are not allowed to be interpreted, as it could lead to a deadlock or emulator crash. This also applies to modules belonging to the Debugger application.

  Breakpoints

Breakpoints are specified on a line basis. When a process executing code in an interpreted module reaches a breakpoint, it stops. This means that a breakpoint must be set at an executable line, that is, a code line containing an executable expression.

A breakpoint has the following:

    • status, which is active or inactive. An inactive breakpoint is ignored.

    • trigger action. When a breakpoint is reached, the trigger action specifies if the breakpoint is to continue as active (enable), or to become inactive (disable), or to be removed (delete).

    • Optionally an associated condition. A condition is a tuple {Module,Name}. When the breakpoint is reached, Module:Name(Bindings) is called. If it evaluates to true, execution stops. If it evaluates to false, the breakpoint is ignored. Bindings contains the current variable bindings. To retrieve the value for a specified variable use get_binding/2.

By default, a breakpoint is active, has trigger action enable, and has no associated condition. For details about breakpoints, see Breakpoints and Break Dialog Windows in the User's Guide for Debugger.

FUNCTIONS

action_at_break(Module, Line, Action) -> ok when Module :: module(), Line :: integer(), Action :: enable | disable | delete.

    Sets the trigger action of the breakpoint at Line in Module to Action.
all_breaks() -> [Break] when Break :: {Point, Options}, Point :: {Module, Line}, Module :: module(), Line :: integer(), Options :: [Status | Trigger | null | Cond], Status :: active | inactive, Trigger :: enable | disable | delete, Cond :: null | Function, Function :: {Module, Name}, Name :: atom().

    Gets all breakpoints.
all_breaks(Module) -> [Break] when Break :: {Point, Options}, Point :: {Module, Line}, Module :: module(), Line :: integer(), Options :: [Status | Trigger | null | Cond], Status :: active | inactive, Trigger :: enable | disable | delete, Cond :: null | Function, Function :: {Module, Name}, Name :: atom().

    Gets all breakpoints in module Module.
auto_attach() -> false | {Flags, Function} when Flags :: [init | break | exit], Function :: {Module, Name, Args}, Module :: module(), Name :: atom(), Args :: [term()].

    Gets how to attach automatically to a process executing code in interpreted modules.

    See auto_attach/2 for the meaning of the possible values in Flags.
auto_attach(false) -> term().

    Disables auto attach.
auto_attach(Flags, Function) -> term() when Flags :: [init | break | exit], Function :: {Module, Name, Args}, Module :: module(), Name :: atom(), Args :: [term()].

    Sets when and how to attach automatically to a process executing code in interpreted modules.

    By default when the interpreter is started, automatic attach is disabled.

    If Flags is an empty list, automatic attach is disabled.

    Otherwise Flags should be a list containing at least one of the following flags: init
        Attach when a process for the first time calls an interpreted function.
    break
        Attach whenever a process reaches a breakpoint.
    exit
        Attach when a process terminates.

    When the specified event occurs, the function Function is called as:

        spawn(Module, Name, [Pid | Args])

    Pid is the pid of the process executing interpreted code.
break(Module, Line) -> ok | {error, break_exists} when Module :: module(), Line :: integer().

    Creates a breakpoint at Line in Module.
break_in(Module, Name, Arity) -> ok | {error, function_not_found} when Module :: module(), Name :: atom(), Arity :: integer().

    Creates a breakpoint at the first line of every clause of function Module:Name/Arity.
clear() -> ok.

    Clears information about processes executing interpreted code by removing all information about terminated processes.
continue(Pid :: pid()) -> ok | {error, not_interpreted}.

    Resumes process execution for Pid.
continue(X, Y, Z) -> ok | {error, not_interpreted} when X :: integer(), Y :: integer(), Z :: integer().

    Resumes process execution for pid(X, Y, Z).
del_break_in(Module, Name, Arity) -> ok | {error, function_not_found} when Module :: module(), Name :: atom(), Arity :: integer().

    Deletes the breakpoints at the first line of every clause of function Module:Name/Arity.
delete_break(Module, Line) -> ok when Module :: module(), Line :: integer().

    Deletes the breakpoint at Line in Module.
disable_break(Module, Line) -> ok when Module :: module(), Line :: integer().

    Makes the breakpoint at Line in Module inactive.
enable_break(Module, Line) -> ok when Module :: module(), Line :: integer().

    Makes the breakpoint at Line in Module active.
file(Module) -> File | {error, not_loaded} when Module :: module(), File :: file:filename_all().

    Returns the source code filename File for an interpreted module Module.
get_binding(Var, Bindings) -> {value, Value} | unbound when Var :: atom(), Bindings :: term(), Value :: term().

    Retrieves the binding of Var from Bindings.

    This function is intended to be used by the conditional function of a breakpoint.
i(AbsModules | AbsModule) -> Result when AbsModules :: [AbsModule, ...], AbsModule :: Module | File, Module :: module(), File :: file:name_all(), Result :: AbsModuleResult | AbsModulesResult, AbsModuleResult :: {module, Module} | error, AbsModulesResult :: ok.

    Interprets the specified module(s) on the local node.

    A module can be specified by its module name (atom) or filename.

    If specified by its module name, the object code Module.beam is searched for in the current path. The source code Module.erl is searched for first in the same directory as the object code, then in an src directory next to it.

    If specified by its filename, the filename can include a path and the .erl extension can be omitted. The object code Module.beam is searched for first in the same directory as the source code, then in an ebin directory next to it, and then in the current path.

    NOTE: The interpreter requires both the source code and the object code. The object code must include debug information, that is, only modules compiled with option debug_info can be interpreted.

    The functions returns {module,Module} if the module was interpreted, otherwise error is returned.

    The argument can also be a list of modules or filenames, in which case the function tries to interpret each module as specified earlier. The function then always returns ok, but prints some information to stdout if a module cannot be interpreted.
interpretable(AbsModule) -> true | {error, Reason} when AbsModule :: Module | File, Module :: module(), File :: file:name_all(), Reason :: no_src | no_beam | no_debug_info | badarg | {app, App}, App :: atom().

    Checks if a module can be interpreted.

    The module can be specified by its module name Module or its source filename File. If specified by a module name, the module is searched for in the code path.

    The function returns true if all of the following apply:

        • Both source code and object code for the module is found.

        • The module has been compiled with option debug_info set.

        • The module does not belong to any of the applications Kernel, STDLIB, WX, or Debugger.

    The function returns {error,Reason} if the module cannot be interpreted. Reason can have the following values: no_src
        No source code is found. It is assumed that the source code and object code are located either in the same directory, or in src and ebin directories next to each other.
    no_beam
        No object code is found. It is assumed that the source code and object code are located either in the same directory, or in src and ebin directories next to each other.
    no_debug_info
        The module has not been compiled with option debug_info set.
    badarg
        AbsModule is not found. This could be because the specified file does not exist, or because code:which/1 does not return a BEAM filename, which is the case not only for non-existing modules but also for modules that are preloaded or cover-compiled.
    {app,App}
        App is kernel, stdlib, gs, or debugger if AbsModule belongs to one of these applications.

    Notice that the function can return true for a module that is not interpretable the module is marked as sticky or resides in a directory marked as sticky. The reason is that this is not discovered until the interpreter tries to load the module.
interpreted() -> [Module] when Module :: module().

    Returns a list with all interpreted modules.
n(AbsModule) -> ok when AbsModule :: Module | File | [Module | File], Module :: module(), File :: file:name_all().

    Stops interpreting the specified module on the local node.

    Similar to i/1 and ni/1, a module can be specified by its module name or filename.
ni(AbsModules | AbsModule) -> Result when AbsModules :: [AbsModule], AbsModule :: Module | File, Module :: module(), File :: file:name_all(), Result :: AbsModuleResult | AbsModulesResult, AbsModuleResult :: {module, Module} | error, AbsModulesResult :: ok.

    Interprets the specified module(s) on all known nodes.

    A module can be specified by its module name (atom) or filename.

    If specified by its module name, the object code Module.beam is searched for in the current path. The source code Module.erl is searched for first in the same directory as the object code, then in an src directory next to it.

    If specified by its filename, the filename can include a path and the .erl extension can be omitted. The object code Module.beam is searched for first in the same directory as the source code, then in an ebin directory next to it, and then in the current path.

    NOTE: The interpreter requires both the source code and the object code. The object code must include debug information, that is, only modules compiled with option debug_info can be interpreted.

    The functions returns {module,Module} if the module was interpreted, otherwise error is returned.

    The argument can also be a list of modules or filenames, in which case the function tries to interpret each module as specified earlier. The function then always returns ok, but prints some information to stdout if a module cannot be interpreted.
nn(AbsModule) -> ok when AbsModule :: Module | File | [Module | File], Module :: module(), File :: file:name_all().

    Stops interpreting the specified module on all known nodes.

    Similar to i/1 and ni/1, a module can be specified by its module name or filename.
no_break() -> ok.

    Deletes all breakpoints.
no_break(Module :: term()) -> ok.

    Deletes all breakpoints in Module.
snapshot() -> [Snapshot] when Snapshot :: {Pid, Function, Status, Info}, Pid :: pid(), Function :: {Module, Name, Args}, Module :: module(), Name :: atom(), Args :: [term()], Status :: idle | running | waiting | break | exit | no_conn, Info :: {} | {Module, Line} | ExitReason, Line :: integer(), ExitReason :: term().

    Gets information about all processes executing interpreted code. Pid
        Process identifier.
    Function
        First interpreted function called by the process.
    Status
        Current status of the process.
    Info
        More information.

    Status is one of the following: idle
        The process is no longer executing interpreted code. Info is {}.
    running
        The process is running. Info is {}.
    waiting
        The process is waiting at a receive. Info is {}.
    break
        Process execution is stopped, normally at a breakpoint. Info is {Module,Line}.
    exit
        The process is terminated. Info is ExitReason.
    no_conn
        The connection is down to the node where the process is running. Info is {}.
stack_trace() -> Flag when Flag :: all | no_tail | false.

    Gets how to save call frames in the stack.

    See stack_trace/1 for the meaning of Flag.
stack_trace(Flag) -> term() when Flag :: all | no_tail | false.

    Sets how to save call frames in the stack.

    Saving call frames makes it possible to inspect the call chain of a process, and is also used to emulate the stack trace if an error (an exception of class error) occurs. The following flags can be specified: all
        Save information about all current calls, that is, function calls that have not yet returned a value.
    no_tail
        Save information about current calls, but discard previous information when a tail-recursive call is made. This option consumes less memory and can be necessary to use for processes with long lifetimes and many tail-recursive calls. This is the default.
    false
        Save no information about current calls.
test_at_break(Module, Line, Function) -> ok when Module :: module(), Line :: integer(), Function :: {Module, Name}, Name :: atom().

    Sets the conditional test of the breakpoint at Line in Module to Function.

    Function Function must fulfill the requirements specified in section Breakpoints.