int(3erl) Erlang Module Definition int(3erl)
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 User's Guide and debugger(3erl).
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 in-
terpreted 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 GS 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 applica-
tion.
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:
* A status, which is active or inactive. An inactive breakpoint is
ignored.
* A 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 {Mod-
ule,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.
By default, a breakpoint is active, has trigger action enable, and has
no associated condition. For details about breakpoints, see the User's
Guide.
EXPORTS
i(AbsModule) -> {module,Module} | error
i(AbsModules) -> ok
ni(AbsModule) -> {module,Module} | error
ni(AbsModules) -> ok
Types:
AbsModules = [AbsModule]
AbsModule = Module | File | [Module | File]
Module = atom()
File = string()
Interprets the specified module(s). i/1 interprets the module
only at the current node. ni/1 interprets the module at 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 Mod-
ule.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 set can be inter-
preted.
The functions returns {module,Module} if the module was inter-
preted, 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 speci-
fied earlier. The function then always returns ok, but prints
some information to stdout if a module cannot be interpreted.
n(AbsModule) -> ok
nn(AbsModule) -> ok
Types:
AbsModule = Module | File | [Module | File]
Module = atom()
File = string()
Stops interpreting the specified module. n/1 stops interpreting
the module only at the current node. nn/1 stops interpreting the
module at all known nodes.
As for i/1 and ni/1, a module can be specified by its module
name or filename.
interpreted() -> [Module]
Types:
Module = atom()
Returns a list with all interpreted modules.
file(Module) -> File | {error,not_loaded}
Types:
Module = atom()
File = string()
Returns the source code filename File for an interpreted module
Module.
interpretable(AbsModule) -> true | {error,Reason}
Types:
AbsModule = Module | File
Module = atom()
File = string()
Reason = no_src | no_beam | no_debug_info | badarg |
{app,App}
App = atom()
Checks if a module can be interpreted. The module can be speci-
fied 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 Ker-
nel, STDLIB, GS, or Debugger.
The function returns {error,Reason} if the module cannot be in-
terpreted. 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 in
fact is not interpretable in the case where 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.
auto_attach() -> false | {Flags,Function}
auto_attach(false)
auto_attach(Flags, Function)
Types:
Flags = [init | break | exit]
Function = {Module,Name,Args}
Module = Name = atom()
Args = [term()]
Gets and sets when and how to attach automatically to a process
executing code in interpreted modules. false means never attach
automatically, this is the default. Otherwise automatic attach
is defined by a list of flags and a function. The following
flags can be specified:
* init - Attach when a process for the first time calls an in-
terpreted 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.
stack_trace() -> Flag
stack_trace(Flag)
Types:
Flag = all | no_tail | false
Gets and 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 ex-
ception of class error) occurs. The following flags can be spec-
ified:
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 pro-
cesses with long lifetimes and many tail recursive calls.
This is the default.
false:
Save no information about currentcalls.
break(Module, Line) -> ok | {error,break_exists}
Types:
Module = atom()
Line = int()
Creates a breakpoint at Line in Module.
delete_break(Module, Line) -> ok
Types:
Module = atom()
Line = int()
Deletes the breakpoint at Line in Module.
break_in(Module, Name, Arity) -> ok | {error,function_not_found}
Types:
Module = Name = atom()
Arity = int()
Creates a breakpoint at the first line of every clause of func-
tion Module:Name/Arity.
del_break_in(Module, Name, Arity) -> ok | {error,function_not_found}
Types:
Module = Name = atom()
Arity = int()
Deletes the breakpoints at the first line of every clause of
function Module:Name/Arity.
no_break() -> ok
no_break(Module) -> ok
Deletes all breakpoints, or all breakpoints in Module.
disable_break(Module, Line) -> ok
Types:
Module = atom()
Line = int()
Makes the breakpoint at Line in Module inactive.
enable_break(Module, Line) -> ok
Types:
Module = atom()
Line = int()
Makes the breakpoint at Line in Module active.
action_at_break(Module, Line, Action) -> ok
Types:
Module = atom()
Line = int()
Action = enable | disable | delete
Sets the trigger action of the breakpoint at Line in Module to
Action.
test_at_break(Module, Line, Function) -> ok
Types:
Module = atom()
Line = int()
Function = {Module,Name}
Name = atom()
Sets the conditional test of the breakpoint at Line in Module to
Function. The function must fulfill the requirements specified
in section Breakpoints.
get_binding(Var, Bindings) -> {value,Value} | unbound
Types:
Var = atom()
Bindings = term()
Value = term()
Retrieves the binding of Var. This function is intended to be
used by the conditional function of a breakpoint.
all_breaks() -> [Break]
all_breaks(Module) -> [Break]
Types:
Break = {Point,Options}
Point = {Module,Line}
Module = atom()
Line = int()
Options = [Status,Trigger,null,Cond|]
Status = active | inactive
Trigger = enable | disable | delete
Cond = null | Function
Function = {Module,Name}
Name = atom()
Gets all breakpoints, or all breakpoints in Module.
snapshot() -> [Snapshot]
Types:
Snapshot = {Pid, Function, Status, Info}
Pid = pid()
Function = {Module,Name,Args}
Module = Name = atom()
Args = [term()]
Status = idle | running | waiting | break | exit | no_conn
Info = {} | {Module,Line} | ExitReason
Line = int()
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={}.
* running - The process is running. Info={}.
* waiting - The process is waiting at a receive. Info={}.
* break - Process execution is stopped, normally at a break-
point. Info={Module,Line}.
* exit - The process is terminated. Info=ExitReason.
* no_conn - The connection is down to the node where the
process is running. Info={}.
clear() -> ok
Clears information about processes executing interpreted code by
removing all information about terminated processes.
continue(Pid) -> ok | {error,not_interpreted}
continue(X,Y,Z) -> ok | {error,not_interpreted}
Types:
Pid = pid()
X = Y = Z = int()
Resumes process execution for Pid or c:pid(X,Y,Z).
Ericsson AB debugger 5.0 int(3erl)