YOU NEED TO KNOW ABOUT POINTER ANALYSIS 10 RULES › pdf › softlab_2012.pdfYOU NEED TO KNOW ABOUT...

POINTER ANALYSIS

EVERYTHINGYOU NEED TO KNOW ABOUT

10 RULESGeorge Kastrinis ~ University of Athens ~ PLAST lab

BASED ON WORK FROM

● “Efficient and Effective Handling of Exceptions in Java Points-To Analysis” Kastrinis G., Smaragdakis Y. (CC'13)

● “Pick Your Contexts Well: Understanding Object-Sensitivity” Smaragdakis Y., Bravenboer M., Lhoták O. (POPL'11)

● “Strictly Declarative Specification of Sophisticated Points-to Analyses” Bravenboer M., Smaragdakis Y. (OOPSLA'09)

University of Athens ~ PL lab (PLAST)

Yannis Smaragdakis George Kastrinis George Balatsouras

Aggelos Biboudis Kostas Ferles George Kollias Prodromos Gerakios

George Kastrinis ~ University of Athens ~ PLAST lab

IN SHORT: WHAT OBJECTS CAN A VARIABLE POINT TO?

void foo() {a = new A1();b = id(a);

void bar() {a = new A2();b = id(a);

A id(A a) {return a;

foo::a new A1()→bar::a new A2()→

Represent objects as

allocation sites

foo::a new A1()→bar::a new A2()→ id::a new A1(), new A2()→

foo::a new A1()→bar::a new A2()→ id::a new A1(), new A2()→foo::b new A1(), new A2()→bar::b new A1(), new A2()→

Not the most precise, right?

Add “context” to variables

foo::a new A1()→bar::a new A2()→ id::a (foo) new A1()→ id::a (bar) new A2()→

foo::a new A1()→bar::a new A2()→ id::a (foo) new A1()→ id::a (bar) new A2()→foo::b new A1()→bar::b new A2()→

10 RULES? NO ALGORITHMS?

Using Datalog

Using Datalog Purely declarative

de·clar·a·tive/di kle( )r tiv/ˈ ə ə

Computing denoting high-level programming languages which can be used to solve problems without requiring the programmer to specify an exact procedure to be followed.

Adjective

~ Oxford dictionaries

de·clar·a·tive/di kle( )r tiv/ˈ ə ə

Computing denoting high-level programming languages which can be used to solve problems without requiring the programmer to specify an exact procedure to be followed.

Adjective

~ Oxford dictionaries

From algorithms to specifications

Datalog Rules

INTERPROCASSIGN(to, calleeCtx, from, callerCtx) ←

CALLGRAPH(invo, callerCtx, meth, calleeCtx),

ACTUALARG(invo, i, from), FORMALARG(meth, i, to).

Datalog Rules

Output relations in red

Datalog Rules

Input relations in blue

Datalog Rules

#1meth(..,from,..)

Datalog Rules#1

invo: meth(..,from,..)meth(..,to,..) {

callerCtx calleeCtx

meth(..,from,..)

Datalog Rules#1

invo: meth(..,from,..)meth(..,to,..) {

meth(..,from,..)

callerCtx calleeCtx

Datalog Rules

INTERPROCASSIGN(to, callerCtx, from, calleeCtx) ←

ACTUALRETURN(invo, to), FORMALRETURN(meth, from).

#2to = meth(..)

Datalog Rules

#2to = meth(..)

invo: to = meth(..)meth(..) { .. return from;}

callerCtx calleeCtx

Datalog Rules

#2to = meth(..)

invo: to = meth(..)meth(..) { .. return from;}

calleeCtxcallerCtx

Datalog Rules

RECORD(heap, ctx) = hctx,

VARPOINTSTO(var, ctx, heap, hctx) ←

REACHABLE(meth, ctx), ALLOC(var, heap, meth).

#3var = new A()

Datalog Rules

#3var = new A()

var = new A();

Datalog Rules

#3var = new A()

var = new A(); heap

new context!

Datalog Rules

#3var = new A()

var = new A(); heap

Datalog Rules

VARPOINTSTO(to, ctx, heap, hctx) ←

VARPOINTSTO(from, ctx, heap, hctx), MOVE(to, from).

#4to = from

Datalog Rules

#4to = from

Datalog Rules

#4to = from

Datalog Rules

#4to = from

Datalog Rules

#4to = from

Recursion!

Datalog Rules#5to ≈ from

VARPOINTSTO(to, toCtx, heap, hctx) ←

INTERPROCASSIGN(to, toCtx, from, fromCtx),

VARPOINTSTO(from, fromCtx, heap, hctx).

fromCtx

Datalog Rules#6base.fld = from

FLDPOINTSTO(baseH, baseHCtx, fld, heap, hctx) ←

VARPOINTSTO(from, ctx, heap, hctx),

STORE(base, fld, from), VARPOINTSTO(base, ctx, baseH, baseHCtx).

hctxfrom

fldbaseH

baseHCtx

hctxfrom

fldbaseH

baseHCtx

Datalog Rules#7to = base.fld

VARPOINTSTO(base, ctx, baseH, baseHCtx),

FLDPOINTSTO(baseH, baseHCtx, fld, heap, hctx), LOAD(to, base, fld).

ctx baseH

baseHCtx

ctx baseH

baseHCtx

ctx baseH

baseHCtx

ctx baseH

baseHCtx

Datalog Rules#8A::toMeth()

MERGESTATIC(invo, callerCtx) = calleeCtx,

REACHABLE(toMeth, calleeCtx),

CALLGRAPH(invo, callerCtx, toMeth, calleeCtx) ←

SCALL(toMeth, invo, inMeth), REACHABLE(inMeth, callerCtx).

invo: A::toMeth(..)

inMeth

callerCtx

toMeth

invo: A::toMeth(..)

inMeth

callerCtx

toMeth

callerCtx

new context!

invo: A::toMeth(..)

inMeth

callerCtx

toMeth

calleeCtx

Datalog Rules#9MERGE(heap, hctx, invo, callerCtx) = calleeCtx,

VARPOINTSTO(this, calleeCtx, heap, hctx),

REACHABLE(inMeth, callerCtx), VCALL(base, sig, invo, inMeth),

VARPOINTSTO(base, callerCtx, heap, hctx),

HEAPTYPE(heap, heapT), LOOKUP(heapT, sig, toMeth),

THISVAR(toMeth, this).

base.sig(..)!!

invo: base.sig(..)

inMeth

callerCtx

base.sig(..)!!

invo: base.sig(..)

inMeth

callerCtx heap

base.sig(..)!!

invo: base.sig(..)

inMeth

callerCtx heap

hctx this

toMeth

base.sig(..)!!

invo: base.sig(..)

inMeth

callerCtx heap

hctx this

toMeth

calleeCtx

new context!

base.sig(..)!!

invo: base.sig(..)

inMeth

callerCtx heap

hctx this

toMeth

calleeCtx

base.sig(..)!!

invo: base.sig(..)

inMeth

callerCtx heap

hctx this

toMeth

calleeCtx

Datalog Rules#10

9 RULES ARE ENOUGH!

Variety of Analyses

Just alter the definition of “context”

LET'S RECALL WHERE CONTEXTS ARE CREATED

MERGE(heap, hctx, invo, callerCtx) = calleeCtx,

Method invocation

Object allocation

CONTEXT INSENSITIVEIGNORE CONTEXT ALTOGETHER

RECORD(heap, ctx) = *

MERGE(heap, hctx, invo, callerCtx) = *

MERGESTATIC(invo, callerCtx) = *

Use a single context everywhere!

CALL-SITE SENSITIVITYUSE CALL-SITES AS CONTEXTS

foo::a new A1()→bar::a new A2()→ id::a (inv1) new A1()→ id::a (inv2) new A2()→foo::b new A1()→bar::b new A2()→

1-CALL-SITE SENSITIVEContext's depth

1-CALL-SITE SENSITIVE

No context for heap abstractions

1-CALL-SITE SENSITIVE

MERGE(heap, hctx, invo, callerCtx) = invo

MERGESTATIC(invo, callerCtx) = invo

1-CALL-SITE SENSITIVE+1-HEAP

Context sensitive heap abstractions

RECORD(heap, ctx) = ctx

MERGE(heap, hctx, invo, callerCtx) = invo

MERGESTATIC(invo, callerCtx) = invo

OBJECT SENSITIVITYUSE ALLOCATION-SITES AS CONTEXTS

Based on the receiverobject in a method call

Really good for Object-Oriented languages

class C {void meth(Object o) { ... }

class Client {void bar(C c1, C c2) {

...c1.meth(obj1);...c2.meth(obj2);

#contexts for meth::o?

#objects (and which) c1 and c2 point to?

1-OBJECT SENSITIVE

No context for heap abstractions

1-OBJECT SENSITIVE

MERGE(heap, hctx, invo, callerCtx) = heap

Use the allocation-site of the receiver object

1-OBJECT SENSITIVE

MERGESTATIC(invo, callerCtx) = ctx

No receiver object to use!

1-OBJECT SENSITIVE

MERGESTATIC(invo, callerCtx) = ctx

No receiver object to use!

Copy context from caller

AND NOW?

● DIFFERENT CONTEXT DEPTHS

AND NOW?

● ALTER DEFINITIONS OF RECORD AND MERGE

AND NOW?

● OTHER TYPES OF CONTEXT

AND NOW?

● COMBINE DIFFERENT CONTEXTS

AND NOW?

● COMBINE DIFFERENT CONTEXTSWhat to combine? Where? How?

9 Rules 3 Context Functions

x = ∞ Analyses

Hope you enjoyed!http://gkastrinis.infoGeorge Kastrinis ●

YOU NEED TO KNOW ABOUT POINTER ANALYSIS 10 RULES › pdf › softlab_2012.pdfYOU NEED TO KNOW ABOUT...

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