Implementing New Stmts in Soot
See the doc of soot.AbstractUnit for some of the most important
functions:
/** * Returns a deep clone of this object. */ @Override public abstract Object clone(); /** * Returns a list of Boxes containing Values used in this Unit. The list * of boxes is dynamically updated as the structure changes. Note that * they are returned in usual evaluation order. (this is important for * aggregation) */ @Override public List<ValueBox> getUseBoxes() { return Collections.emptyList(); } /** * Returns a list of Boxes containing Values defined in this Unit. The * list of boxes is dynamically updated as the structure changes. */ @Override public List<ValueBox> getDefBoxes() { return Collections.emptyList(); } /** * Used to implement the Switchable construct. */ @Override public void apply(Switch sw) { }
1. Stmt With No Operand
If the new stmt has no operand in it, like NopStmt, simply extend
AbstractStmt. See JNopStmt for example.
When implementing a new stmt (e.g. TbtStmt), you need to override the
apply() function. This also requires adding caseTbtStmt() to
StmtSwitches. However, chaning the StmtSwitch interface would break
lots of code. Instead, an easier solution would be to just implement
apply() in TbtStmt like this:
public void apply(Switch sw) { if (sw instanceof AbstractStmtSwitch) ((AbstractStmtSwitch<?>) sw).caseTbtStmt(this); }
and add caseTbtStmt() to AbstractStmtSwitch:
public void caseTbtStmt(TbtStmt stmt) { defaultCase(stmt); }
This way, only one source file within Soot needs to be changed.
2. Stmt With One Operand
Some body transformations (e.g. LocalPacker) will change the Locals
in a Body. If a stmt uses (or defines) an operand, it must return it
in getUseBoxes() or getDefBoxes(). Otherwise, that operand will not
be updated during the transformation.
Some examples of stmts with one operand: JThrowStmt,
JEnterMonitorStmt, and JExitMonitorStmt. They all extend
AbstractOpStmt.