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Merge pull request #4277 from 9rnsr/fix13902
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Issue 13902 - Compiler allows escaping the address of part of a local
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@WalterBright
WalterBright committed Jan 11, 2015
2 parents 0dd8abd + 8488306 commit 0829ec3
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321 changes: 321 additions & 0 deletions src/escape.c
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/* Compiler implementation of the D programming language
* Copyright (c) 1999-2015 by Digital Mars
* All Rights Reserved
* written by Walter Bright
* http://www.digitalmars.com
* Distributed under the Boost Software License, Version 1.0.
* http://www.boost.org/LICENSE_1_0.txt
* https://github.com/D-Programming-Language/dmd/blob/master/src/escape.c
*/

#include "init.h"
#include "expression.h"
#include "scope.h"
#include "declaration.h"

/************************************
* Detect cases where pointers to the stack can 'escape' the
* lifetime of the stack frame.
*/

void checkEscape(Scope *sc, Expression *e)
{
//printf("[%s] checkEscape, e = %s\n", e->loc.toChars(), e->toChars());

class EscapeVisitor : public Visitor
{
public:
Scope *sc;

EscapeVisitor(Scope *sc)
: sc(sc)
{
}

void check(Loc loc, Declaration *d)
{
VarDeclaration *v = d->isVarDeclaration();
if (v && v->toParent2() == sc->func)
{
if (v->isDataseg())
return;
if ((v->storage_class & (STCref | STCout)) == 0)
error(loc, "escaping reference to local %s", v->toChars());
}
}

void visit(Expression *e)
{
}

void visit(AddrExp *e)
{
checkEscapeRef(sc, e->e1);
}

void visit(SymOffExp *e)
{
check(e->loc, e->var);
}

void visit(VarExp *e)
{
VarDeclaration *v = e->var->isVarDeclaration();
if (v)
{
Type *tb = v->type->toBasetype();
if (v->isScope())
{
/* Today, scope attribute almost doesn't work for escape analysis.
* Until the semantics will be completed, it should be left as-is.
* See also: fail_compilation/fail_scope.d
*/
if (tb->ty == Tarray || tb->ty == Tsarray || tb->ty == Tclass || tb->ty == Tdelegate)
{
if ((!v->noscope || tb->ty == Tclass))
{
e->error("escaping reference to scope local %s", v->toChars());
return;
}
}
}
if (v->storage_class & STCvariadic)
{
if (tb->ty == Tarray || tb->ty == Tsarray)
e->error("escaping reference to variadic parameter %s", v->toChars());
}
}
}

void visit(TupleExp *e)
{
for (size_t i = 0; i < e->exps->dim; i++)
{
checkEscape(sc, (*e->exps)[i]);
}
}

void visit(ArrayLiteralExp *e)
{
Type *tb = e->type->toBasetype();
if (tb->ty == Tsarray || tb->ty == Tarray)
{
for (size_t i = 0; i < e->elements->dim; i++)
{
checkEscape(sc, (*e->elements)[i]);
}
}
}

void visit(StructLiteralExp *e)
{
for (size_t i = 0; i < e->elements->dim; i++)
{
checkEscape(sc, (*e->elements)[i]);
}
}

void visit(NewExp *e)
{
Type *tb = e->newtype->toBasetype();
if (tb->ty == Tstruct && !e->member && e->arguments)
{
for (size_t i = 0; i < e->arguments->dim; i++)
{
checkEscape(sc, (*e->arguments)[i]);
}
}
}

void visit(CastExp *e)
{
Type *tb = e->type->toBasetype();
if (tb->ty == Tarray &&
e->e1->op == TOKvar &&
e->e1->type->toBasetype()->ty == Tsarray)
{
VarExp *ve = (VarExp *)e->e1;
VarDeclaration *v = ve->var->isVarDeclaration();
if (v && v->toParent2() == sc->func)
{
if (!v->isDataseg() && !v->isParameter())
e->error("escaping reference to local %s", v->toChars());
}
}
}

void visit(SliceExp *e)
{
if (e->e1->op == TOKvar)
{
VarDeclaration *v = ((VarExp *)e->e1)->var->isVarDeclaration();
Type *tb = e->type->toBasetype();
if (v)
{
if (tb->ty == Tsarray)
return;
if (v->storage_class & STCvariadic)
{
e->error("escaping reference to the payload of variadic parameter %s", v->toChars());
return;
}
}
}
Type *t1b = e->e1->type->toBasetype();
if (t1b->ty == Tsarray)
checkEscapeRef(sc, e->e1);
else
checkEscape(sc, e->e1);
}

void visit(BinExp *e)
{
Type *tb = e->type->toBasetype();
if (tb->ty == Tpointer)
{
checkEscape(sc, e->e1);
checkEscape(sc, e->e2);
}
}

void visit(BinAssignExp *e)
{
checkEscape(sc, e->e2);
}

void visit(AssignExp *e)
{
checkEscape(sc, e->e2);
}

void visit(CommaExp *e)
{
checkEscape(sc, e->e2);
}

void visit(CondExp *e)
{
checkEscape(sc, e->e1);
checkEscape(sc, e->e2);
}
};

EscapeVisitor v(sc);
e->accept(&v);
}

void checkEscapeRef(Scope *sc, Expression *e)
{
//printf("[%s] checkEscapeRef, e = %s\n", e->loc.toChars(), e->toChars());

class EscapeRefVisitor : public Visitor
{
public:
Scope *sc;

EscapeRefVisitor(Scope *sc)
: sc(sc)
{
}

void check(Loc loc, Declaration *d)
{
VarDeclaration *v = d->isVarDeclaration();
if (v && v->toParent2() == sc->func)
{
if (v->isDataseg())
return;
if ((v->storage_class & (STCref | STCout)) == 0)
{
error(loc, "escaping reference to local variable %s", v->toChars());
return;
}
if ((v->storage_class & (STCref | STCtemp)) == (STCref | STCtemp) &&
v->init)
{
// (ref v = ex; ex)
if (ExpInitializer *ez = v->init->isExpInitializer())
{
assert(ez->exp && ez->exp->op == TOKconstruct);
Expression *ex = ((ConstructExp *)ez->exp)->e2;
checkEscapeRef(sc, ex);
return;
}
}
}
}

void visit(Expression *e)
{
}

void visit(VarExp *e)
{
check(e->loc, e->var);
}

void visit(PtrExp *e)
{
checkEscape(sc, e->e1);
}

void visit(IndexExp *e)
{
if (e->e1->op == TOKvar)
{
VarDeclaration *v = ((VarExp *)e->e1)->var->isVarDeclaration();
if (v && v->toParent2() == sc->func)
{
Type *tb = v->type->toBasetype();
if (tb->ty == Tarray || tb->ty == Tsarray)
{
if (v->storage_class & STCvariadic)
{
e->error("escaping reference to the payload of variadic parameter %s", v->toChars());
return;
}
}
}
}

Type *tb = e->e1->type->toBasetype();
if (tb->ty == Tsarray)
{
checkEscapeRef(sc, e->e1);
}
}

void visit(DotVarExp *e)
{
Type *t1b = e->e1->type->toBasetype();
if (t1b->ty == Tclass)
checkEscape(sc, e->e1);
else
checkEscapeRef(sc, e->e1);
}

void visit(BinAssignExp *e)
{
checkEscapeRef(sc, e->e1);
}

void visit(AssignExp *e)
{
checkEscapeRef(sc, e->e1);
}

void visit(CommaExp *e)
{
checkEscapeRef(sc, e->e2);
}

void visit(CondExp *e)
{
checkEscapeRef(sc, e->e1);
checkEscapeRef(sc, e->e2);
}
};
EscapeRefVisitor v(sc);
e->accept(&v);
}

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