stolen / modhack

Some utilities to play with erlang modules

modhack

What is modhack?

modhack is collection of utilities to manipulate wit Erlang modules.

Exported functions

• alias(Target, Alias) --- make an alias for module Target (indeed it is proxy)
• copy(Source, Destination) --- copy module at binary-level
• overlay([Mod1, Mod2|...], ResultName) --- combine modules into one supermodule
• patch(Module, Patch) or patch(Module, [Patch1|...]) --- modify Module so that functions existing in Patches take precedence.

Usage example

Eshell V5.9  (abort with ^G)
1> victim:module_info(exports).
[{fun4,0},{module_info,0},{module_info,1}]
2> modhack:overlay([mod1, mod2, mod3], victim).
{module,victim}
3> victim:module_info(exports).                
[{fun2,0},
 {fun3,0},
 {fun2,1},
 {fun1,0},
 {module_info,0},
 {module_info,1}]
4> victim:fun1().
mod1
5> victim:fun2(x).
{mod2,x}
6> victim:fun2(). 
mod3
7> l(victim), victim:module_info(exports).
[{fun4,0},{module_info,0},{module_info,1}]
8> modhack:patch(victim, mod1), victim:fun1().
mod1

mod1.erl

-module(mod1).
-compile(export_all).
fun1() -> ?MODULE.

mod2.erl

-module(mod2).
-compile(export_all).
fun1() -> ?MODULE.
fun2(Arg) -> {?MODULE, Arg}.

mod3.erl

-module(mod3).
-compile(export_all).
fun2() -> ?MODULE.
fun3() -> ?MODULE.

victim.erl

-module(victim).
-compile(export_all).
fun4() -> ?MODULE.