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escape.d
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escape.d
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/**
* Compiler implementation of the
* $(LINK2 http://www.dlang.org, D programming language).
*
* Copyright: Copyright (c) 1999-2017 by Digital Mars, All Rights Reserved
* Authors: $(LINK2 http://www.digitalmars.com, Walter Bright)
* License: $(LINK2 http://www.boost.org/LICENSE_1_0.txt, Boost License 1.0)
* Source: $(DMDSRC _escape.d)
*/
module ddmd.escape;
import core.stdc.stdio : printf;
import ddmd.aggregate;
import ddmd.declaration;
import ddmd.dscope;
import ddmd.dsymbol;
import ddmd.errors;
import ddmd.expression;
import ddmd.func;
import ddmd.globals;
import ddmd.identifier;
import ddmd.init;
import ddmd.mtype;
import ddmd.root.rootobject;
import ddmd.tokens;
import ddmd.visitor;
import ddmd.arraytypes;
/****************************************
* Function parameter par is being initialized to arg,
* and par may escape.
* Detect if scoped values can escape this way.
* Print error messages when these are detected.
* Params:
* sc = used to determine current function and module
* par = identifier of function parameter
* arg = initializer for param
* gag = do not print error messages
* Returns:
* true if pointers to the stack can escape via assignment
*/
bool checkParamArgumentEscape(Scope* sc, FuncDeclaration fdc, Identifier par, Expression arg, bool gag)
{
//printf("checkParamArgumentEscape(arg: %s par: %s)\n", arg.toChars(), par.toChars());
//printf("type = %s, %d\n", arg.type.toChars(), arg.type.hasPointers());
if (!arg.type.hasPointers())
return false;
EscapeByResults er;
escapeByValue(arg, &er);
if (!er.byref.dim && !er.byvalue.dim && !er.byfunc.dim && !er.byexp.dim)
return false;
bool result = false;
/* 'v' is assigned unsafely to 'par'
*/
void unsafeAssign(VarDeclaration v, const char* desc)
{
if (global.params.vsafe && sc.func.setUnsafe())
{
if (!gag)
error(arg.loc, "%s %s assigned to non-scope parameter %s calling %s",
desc, v.toChars(),
par ? par.toChars() : "unnamed",
fdc ? fdc.toPrettyChars() : "indirectly");
result = true;
}
}
foreach (VarDeclaration v; er.byvalue)
{
//printf("byvalue %s\n", v.toChars());
if (v.isDataseg())
continue;
Dsymbol p = v.toParent2();
v.storage_class &= ~STCmaybescope;
if (v.isScope())
{
unsafeAssign(v, "scope variable");
}
else if (v.storage_class & STCvariadic && p == sc.func)
{
Type tb = v.type.toBasetype();
if (tb.ty == Tarray || tb.ty == Tsarray)
{
unsafeAssign(v, "variadic variable");
}
}
else
{
/* v is not 'scope', and is assigned to a parameter that may escape.
* Therefore, v can never be 'scope'.
*/
v.doNotInferScope = true;
}
}
foreach (VarDeclaration v; er.byref)
{
if (v.isDataseg())
continue;
Dsymbol p = v.toParent2();
v.storage_class &= ~STCmaybescope;
if ((v.storage_class & (STCref | STCout)) == 0 && p == sc.func)
{
unsafeAssign(v, "reference to local variable");
continue;
}
}
foreach (FuncDeclaration fd; er.byfunc)
{
//printf("fd = %s, %d\n", fd.toChars(), fd.tookAddressOf);
VarDeclarations vars;
findAllOuterAccessedVariables(fd, &vars);
foreach (v; vars)
{
//printf("v = %s\n", v.toChars());
assert(!v.isDataseg()); // these are not put in the closureVars[]
Dsymbol p = v.toParent2();
v.storage_class &= ~STCmaybescope;
if ((v.storage_class & (STCref | STCout | STCscope)) && p == sc.func)
{
unsafeAssign(v, "reference to local");
continue;
}
}
}
foreach (Expression ee; er.byexp)
{
if (sc.func.setUnsafe())
{
if (!gag)
error(ee.loc, "reference to stack allocated value returned by %s assigned to non-scope parameter %s",
ee.toChars(),
par ? par.toChars() : "unnamed");
result = true;
}
}
return result;
}
/****************************************
* Given an AssignExp, determine if the lvalue will cause
* the contents of the rvalue to escape.
* Print error messages when these are detected.
* Infer 'scope' for the lvalue where possible, in order
* to eliminate the error.
* Params:
* sc = used to determine current function and module
* ae = AssignExp to check for any pointers to the stack
* gag = do not print error messages
* Returns:
* true if pointers to the stack can escape via assignment
*/
bool checkAssignEscape(Scope* sc, Expression e, bool gag)
{
//printf("checkAssignEscape(e: %s)\n", e.toChars());
if (e.op != TOKassign && e.op != TOKblit && e.op != TOKconstruct)
return false;
auto ae = cast(AssignExp)e;
Expression e1 = ae.e1;
Expression e2 = ae.e2;
//printf("type = %s, %d\n", e1.type.toChars(), e1.type.hasPointers());
if (!e1.type.hasPointers())
return false;
if (e1.op == TOKslice)
return false;
EscapeByResults er;
escapeByValue(e2, &er);
if (!er.byref.dim && !er.byvalue.dim && !er.byfunc.dim && !er.byexp.dim)
return false;
VarDeclaration va;
while (e1.op == TOKdotvar)
e1 = (cast(DotVarExp)e1).e1;
if (e1.op == TOKvar)
va = (cast(VarExp)e1).var.isVarDeclaration();
else if (e1.op == TOKthis)
va = (cast(ThisExp)e1).var.isVarDeclaration();
else if (e1.op == TOKindex)
{
auto ie = cast(IndexExp)e1;
if (ie.e1.op == TOKvar && ie.e1.type.toBasetype().ty == Tsarray)
va = (cast(VarExp)ie.e1).var.isVarDeclaration();
}
// Try to infer 'scope' for va if in a function not marked @system
bool inferScope = false;
if (va && sc.func && sc.func.type && sc.func.type.ty == Tfunction)
inferScope = (cast(TypeFunction)sc.func.type).trust != TRUSTsystem;
bool result = false;
foreach (VarDeclaration v; er.byvalue)
{
//printf("byvalue: %s\n", v.toChars());
if (v.isDataseg())
continue;
if (v == va)
continue;
Dsymbol p = v.toParent2();
if (!(va && va.isScope()))
v.storage_class &= ~STCmaybescope;
if (v.isScope())
{
if (va && va.isScope() && va.storage_class & STCreturn && !(v.storage_class & STCreturn) &&
sc.func.setUnsafe())
{
if (!gag)
error(ae.loc, "scope variable %s assigned to return scope %s", v.toChars(), va.toChars());
result = true;
continue;
}
// If va's lifetime encloses v's, then error
if (va &&
(va.enclosesLifetimeOf(v) && !(v.storage_class & STCparameter) || va.storage_class & STCref) &&
sc.func.setUnsafe())
{
if (!gag)
error(ae.loc, "scope variable %s assigned to %s with longer lifetime", v.toChars(), va.toChars());
result = true;
continue;
}
if (va && !va.isDataseg() && !va.doNotInferScope)
{
if (!va.isScope() && inferScope)
{ //printf("inferring scope for %s\n", va.toChars());
va.storage_class |= STCscope;
va.storage_class |= v.storage_class & STCreturn;
}
continue;
}
if (sc.func.setUnsafe())
{
if (!gag)
error(ae.loc, "scope variable %s assigned to non-scope %s", v.toChars(), e1.toChars());
result = true;
}
}
else if (v.storage_class & STCvariadic && p == sc.func)
{
Type tb = v.type.toBasetype();
if (tb.ty == Tarray || tb.ty == Tsarray)
{
if (va && !va.isDataseg() && !va.doNotInferScope)
{
if (!va.isScope() && inferScope)
{ //printf("inferring scope for %s\n", va.toChars());
va.storage_class |= STCscope;
}
continue;
}
if (sc.func.setUnsafe())
{
if (!gag)
error(ae.loc, "variadic variable %s assigned to non-scope %s", v.toChars(), e1.toChars());
result = true;
}
}
}
else
{
/* v is not 'scope', and we didn't check the scope of where we assigned it to.
* It may escape via that assignment, therefore, v can never be 'scope'.
*/
v.doNotInferScope = true;
}
}
foreach (VarDeclaration v; er.byref)
{
//printf("byref: %s\n", v.toChars());
if (v.isDataseg())
continue;
Dsymbol p = v.toParent2();
// If va's lifetime encloses v's, then error
if (va &&
(va.enclosesLifetimeOf(v) && !(v.storage_class & STCparameter) || va.storage_class & STCref) &&
sc.func.setUnsafe())
{
if (!gag)
error(ae.loc, "address of variable %s assigned to %s with longer lifetime", v.toChars(), va.toChars());
result = true;
continue;
}
if (!(va && va.isScope()))
v.storage_class &= ~STCmaybescope;
if ((v.storage_class & (STCref | STCout)) == 0 && p == sc.func)
{
if (va && !va.isDataseg() && !va.doNotInferScope)
{
if (!va.isScope() && inferScope &&
va.type.toBasetype().ty != Tclass) // scope classes are special
{ //printf("inferring scope for %s\n", va.toChars());
va.storage_class |= STCscope;
}
continue;
}
if (sc.func.setUnsafe())
{
if (!gag)
error(ae.loc, "reference to local variable %s assigned to non-scope %s", v.toChars(), e1.toChars());
result = true;
}
continue;
}
}
foreach (FuncDeclaration fd; er.byfunc)
{
//printf("fd = %s, %d\n", fd.toChars(), fd.tookAddressOf);
VarDeclarations vars;
findAllOuterAccessedVariables(fd, &vars);
foreach (v; vars)
{
//printf("v = %s\n", v.toChars());
assert(!v.isDataseg()); // these are not put in the closureVars[]
Dsymbol p = v.toParent2();
if (!(va && va.isScope()))
v.storage_class &= ~STCmaybescope;
if ((v.storage_class & (STCref | STCout | STCscope)) && p == sc.func)
{
if (va && !va.isDataseg() && !va.doNotInferScope)
{
/* Don't infer STCscope for va, because then a closure
* won't be generated for sc.func.
*/
//if (!va.isScope() && inferScope)
//va.storage_class |= STCscope;
continue;
}
if (sc.func.setUnsafe())
{
if (!gag)
error(ae.loc, "reference to local %s assigned to non-scope %s in @safe code", v.toChars(), e1.toChars());
result = true;
}
continue;
}
}
}
foreach (Expression ee; er.byexp)
{
if (va && !va.isDataseg() && !va.doNotInferScope)
{
if (!va.isScope() && inferScope)
{ //printf("inferring scope for %s\n", va.toChars());
va.storage_class |= STCscope;
}
continue;
}
if (sc.func.setUnsafe())
{
if (!gag)
error(ee.loc, "reference to stack allocated value returned by %s assigned to non-scope %s",
ee.toChars(), e1.toChars());
result = true;
}
}
return result;
}
/************************************
* Detect cases where pointers to the stack can 'escape' the
* lifetime of the stack frame when throwing `e`.
* Print error messages when these are detected.
* Params:
* sc = used to determine current function and module
* e = expression to check for any pointers to the stack
* gag = do not print error messages
* Returns:
* true if pointers to the stack can escape
*/
bool checkThrowEscape(Scope* sc, Expression e, bool gag)
{
//printf("[%s] checkThrowEscape, e = %s\n", e.loc.toChars(), e.toChars());
EscapeByResults er;
escapeByValue(e, &er);
if (!er.byref.dim && !er.byvalue.dim && !er.byexp.dim)
return false;
bool result = false;
foreach (VarDeclaration v; er.byvalue)
{
//printf("byvalue %s\n", v.toChars());
if (v.isDataseg())
continue;
Dsymbol p = v.toParent2();
if (v.isScope())
{
if (sc._module && sc._module.isRoot())
{
// Only look for errors if in module listed on command line
if (global.params.vsafe) // https://issues.dlang.org/show_bug.cgi?id=17029
{
if (!gag)
error(e.loc, "scope variable %s may not be thrown", v.toChars());
result = true;
}
continue;
}
}
else
{
//printf("no infer for %s\n", v.toChars());
v.doNotInferScope = true;
}
}
return result;
}
/************************************
* Detect cases where pointers to the stack can 'escape' the
* lifetime of the stack frame by returning 'e' by value.
* Print error messages when these are detected.
* Params:
* sc = used to determine current function and module
* e = expression to check for any pointers to the stack
* gag = do not print error messages
* Returns:
* true if pointers to the stack can escape
*/
bool checkReturnEscape(Scope* sc, Expression e, bool gag)
{
//printf("[%s] checkReturnEscape, e = %s\n", e.loc.toChars(), e.toChars());
return checkReturnEscapeImpl(sc, e, false, gag);
}
/************************************
* Detect cases where returning 'e' by ref can result in a reference to the stack
* being returned.
* Print error messages when these are detected.
* Params:
* sc = used to determine current function and module
* e = expression to check
* gag = do not print error messages
* Returns:
* true if references to the stack can escape
*/
bool checkReturnEscapeRef(Scope* sc, Expression e, bool gag)
{
version (none)
{
printf("[%s] checkReturnEscapeRef, e = %s\n", e.loc.toChars(), e.toChars());
printf("current function %s\n", sc.func.toChars());
printf("parent2 function %s\n", sc.func.toParent2().toChars());
}
return checkReturnEscapeImpl(sc, e, true, gag);
}
private bool checkReturnEscapeImpl(Scope* sc, Expression e, bool refs, bool gag)
{
//printf("[%s] checkReturnEscapeImpl, e = %s\n", e.loc.toChars(), e.toChars());
EscapeByResults er;
if (refs)
escapeByRef(e, &er);
else
escapeByValue(e, &er);
if (!er.byref.dim && !er.byvalue.dim && !er.byexp.dim)
return false;
bool result = false;
foreach (VarDeclaration v; er.byvalue)
{
//printf("byvalue %s\n", v.toChars());
if (v.isDataseg())
continue;
Dsymbol p = v.toParent2();
if ((v.isScope() || (v.storage_class & STCmaybescope)) &&
!(v.storage_class & STCreturn) &&
v.isParameter() &&
sc.func.flags & FUNCFLAGreturnInprocess &&
p == sc.func)
{
inferReturn(sc.func, v); // infer addition of 'return'
continue;
}
if (v.isScope())
{
if (v.storage_class & STCreturn)
continue;
if (sc._module && sc._module.isRoot() &&
/* This case comes up when the ReturnStatement of a __foreachbody is
* checked for escapes by the caller of __foreachbody. Skip it.
*
* struct S { static int opApply(int delegate(S*) dg); }
* S* foo() {
* foreach (S* s; S) // create __foreachbody for body of foreach
* return s; // s is inferred as 'scope' but incorrectly tested in foo()
* return null; }
*/
!(!refs && p.parent == sc.func))
{
// Only look for errors if in module listed on command line
if (global.params.vsafe) // https://issues.dlang.org/show_bug.cgi?id=17029
{
if (!gag)
error(e.loc, "scope variable %s may not be returned", v.toChars());
result = true;
}
continue;
}
}
else if (v.storage_class & STCvariadic && p == sc.func)
{
Type tb = v.type.toBasetype();
if (tb.ty == Tarray || tb.ty == Tsarray)
{
if (!gag)
error(e.loc, "escaping reference to variadic parameter %s", v.toChars());
result = false;
}
}
else
{
//printf("no infer for %s\n", v.toChars());
v.doNotInferScope = true;
}
}
foreach (VarDeclaration v; er.byref)
{
//printf("byref %s\n", v.toChars());
if (v.isDataseg())
continue;
Dsymbol p = v.toParent2();
if ((v.storage_class & (STCref | STCout)) == 0)
{
if (p == sc.func)
{
if (!gag)
error(e.loc, "escaping reference to local variable %s", v.toChars());
result = true;
continue;
}
FuncDeclaration fd = p.isFuncDeclaration();
if (fd && sc.func.flags & FUNCFLAGreturnInprocess)
{
/* Code like:
* int x;
* auto dg = () { return &x; }
* Making it:
* auto dg = () return { return &x; }
* Because dg.ptr points to x, this is returning dt.ptr+offset
*/
if (global.params.vsafe)
sc.func.storage_class |= STCreturn;
}
}
/* Check for returning a ref variable by 'ref', but should be 'return ref'
* Infer the addition of 'return', or set result to be the offending expression.
*/
if ( (v.storage_class & (STCref | STCout)) &&
!(v.storage_class & (STCreturn | STCforeach)))
{
if (sc.func.flags & FUNCFLAGreturnInprocess && p == sc.func)
{
inferReturn(sc.func, v); // infer addition of 'return'
}
else if (global.params.useDIP25 &&
sc._module && sc._module.isRoot())
{
// Only look for errors if in module listed on command line
if (p == sc.func)
{
//printf("escaping reference to local ref variable %s\n", v.toChars());
//printf("storage class = x%llx\n", v.storage_class);
if (!gag)
error(e.loc, "escaping reference to local variable %s", v.toChars());
result = true;
continue;
}
// Don't need to be concerned if v's parent does not return a ref
FuncDeclaration fd = p.isFuncDeclaration();
if (fd && fd.type && fd.type.ty == Tfunction)
{
TypeFunction tf = cast(TypeFunction)fd.type;
if (tf.isref)
{
if (!gag)
error(e.loc, "escaping reference to outer local variable %s", v.toChars());
result = true;
continue;
}
}
}
}
}
foreach (Expression ee; er.byexp)
{
//printf("byexp %s\n", ee.toChars());
if (!gag)
error(ee.loc, "escaping reference to stack allocated value returned by %s", ee.toChars());
result = true;
}
return result;
}
/*************************************
* Variable v needs to have 'return' inferred for it.
* Params:
* fd = function that v is a parameter to
* v = parameter that needs to be STCreturn
*/
private void inferReturn(FuncDeclaration fd, VarDeclaration v)
{
// v is a local in the current function
//printf("for function '%s' inferring 'return' for variable '%s'\n", fd.toChars(), v.toChars());
v.storage_class |= STCreturn;
TypeFunction tf = cast(TypeFunction)fd.type;
if (v == fd.vthis)
{
/* v is the 'this' reference, so mark the function
*/
fd.storage_class |= STCreturn;
if (tf.ty == Tfunction)
{
//printf("'this' too %p %s\n", tf, sc.func.toChars());
tf.isreturn = true;
}
}
else
{
// Perform 'return' inference on parameter
if (tf.ty == Tfunction && tf.parameters)
{
const dim = Parameter.dim(tf.parameters);
foreach (const i; 0 .. dim)
{
Parameter p = Parameter.getNth(tf.parameters, i);
if (p.ident == v.ident)
{
p.storageClass |= STCreturn;
break; // there can be only one
}
}
}
}
}
/****************************************
* e is an expression to be returned by value, and that value contains pointers.
* Walk e to determine which variables are possibly being
* returned by value, such as:
* int* function(int* p) { return p; }
* If e is a form of &p, determine which variables have content
* which is being returned as ref, such as:
* int* function(int i) { return &i; }
* Multiple variables can be inserted, because of expressions like this:
* int function(bool b, int i, int* p) { return b ? &i : p; }
*
* No side effects.
*
* Params:
* e = expression to be returned by value
* er = where to place collected data
*/
private void escapeByValue(Expression e, EscapeByResults* er)
{
//printf("[%s] escapeByValue, e: %s\n", e.loc.toChars(), e.toChars());
extern (C++) final class EscapeVisitor : Visitor
{
alias visit = super.visit;
public:
EscapeByResults* er;
extern (D) this(EscapeByResults* er)
{
this.er = er;
}
override void visit(Expression e)
{
}
override void visit(AddrExp e)
{
escapeByRef(e.e1, er);
}
override void visit(SymOffExp e)
{
VarDeclaration v = e.var.isVarDeclaration();
if (v)
er.byref.push(v);
}
override void visit(VarExp e)
{
VarDeclaration v = e.var.isVarDeclaration();
if (v)
er.byvalue.push(v);
}
override void visit(ThisExp e)
{
VarDeclaration v = e.var.isVarDeclaration();
if (v)
er.byvalue.push(v);
}
override void visit(DotVarExp e)
{
auto t = e.e1.type.toBasetype();
if (t.ty == Tstruct)
e.e1.accept(this);
}
override void visit(DelegateExp e)
{
er.byfunc.push(e.func);
}
override void visit(FuncExp e)
{
if (e.fd.tok == TOKdelegate)
er.byfunc.push(e.fd);
}
override void visit(TupleExp e)
{
assert(0); // should have been lowered by now
}
override void visit(ArrayLiteralExp e)
{
Type tb = e.type.toBasetype();
if (tb.ty == Tsarray || tb.ty == Tarray)
{
if (e.basis)
e.basis.accept(this);
foreach (el; *e.elements)
{
if (el)
el.accept(this);
}
}
}
override void visit(StructLiteralExp e)
{
if (e.elements)
{
foreach (ex; *e.elements)
{
if (ex)
ex.accept(this);
}
}
}
override void visit(NewExp e)
{
Type tb = e.newtype.toBasetype();
if (tb.ty == Tstruct && !e.member && e.arguments)
{
foreach (ex; *e.arguments)
{
if (ex)
ex.accept(this);
}
}
}
override void visit(CastExp e)
{
Type tb = e.type.toBasetype();
if (tb.ty == Tarray && e.e1.type.toBasetype().ty == Tsarray)
{
escapeByRef(e.e1, er);
}
else
e.e1.accept(this);
}
override void visit(SliceExp e)
{
if (e.e1.op == TOKvar)
{
VarDeclaration v = (cast(VarExp)e.e1).var.isVarDeclaration();
Type tb = e.type.toBasetype();
if (v)
{
if (tb.ty == Tsarray)
return;
if (v.storage_class & STCvariadic)
{
er.byvalue.push(v);
return;
}
}
}
Type t1b = e.e1.type.toBasetype();
if (t1b.ty == Tsarray)
{
Type tb = e.type.toBasetype();
if (tb.ty != Tsarray)
escapeByRef(e.e1, er);
}
else
e.e1.accept(this);
}
override void visit(BinExp e)
{
Type tb = e.type.toBasetype();
if (tb.ty == Tpointer)
{
e.e1.accept(this);
e.e2.accept(this);
}
}
override void visit(BinAssignExp e)
{
e.e1.accept(this);
}
override void visit(AssignExp e)
{
e.e1.accept(this);
}
override void visit(CommaExp e)
{
e.e2.accept(this);
}
override void visit(CondExp e)
{
e.e1.accept(this);
e.e2.accept(this);
}
override void visit(CallExp e)
{
//printf("CallExp(): %s\n", e.toChars());
/* Check each argument that is
* passed as 'return scope'.
*/
Type t1 = e.e1.type.toBasetype();
TypeFunction tf;
TypeDelegate dg;
if (t1.ty == Tdelegate)
{
dg = cast(TypeDelegate)t1;
tf = cast(TypeFunction)(cast(TypeDelegate)t1).next;
}
else if (t1.ty == Tfunction)
tf = cast(TypeFunction)t1;
else
return;
if (e.arguments && e.arguments.dim)
{
/* j=1 if _arguments[] is first argument,
* skip it because it is not passed by ref
*/
int j = (tf.linkage == LINKd && tf.varargs == 1);
for (size_t i = j; i < e.arguments.dim; ++i)
{
Expression arg = (*e.arguments)[i];
size_t nparams = Parameter.dim(tf.parameters);
if (i - j < nparams && i >= j)
{
Parameter p = Parameter.getNth(tf.parameters, i - j);
const stc = tf.parameterStorageClass(p);
if ((stc & (STCscope)) && (stc & STCreturn))
arg.accept(this);
else if ((stc & (STCref)) && (stc & STCreturn))
escapeByRef(arg, er);
}
}
}
// If 'this' is returned, check it too
if (e.e1.op == TOKdotvar && t1.ty == Tfunction)
{
DotVarExp dve = cast(DotVarExp)e.e1;
FuncDeclaration fd = dve.var.isFuncDeclaration();
AggregateDeclaration ad;
if (global.params.vsafe && tf.isreturn && fd && (ad = fd.isThis()) !is null)
{
if (ad.isClassDeclaration() || tf.isscope) // this is 'return scope'
dve.e1.accept(this);
else if (ad.isStructDeclaration()) // this is 'return ref'
escapeByRef(dve.e1, er);
}
else if (dve.var.storage_class & STCreturn || tf.isreturn)
{
if (dve.var.storage_class & STCscope)
dve.e1.accept(this);
else if (dve.var.storage_class & STCref)
escapeByRef(dve.e1, er);
}
}
/* If returning the result of a delegate call, the .ptr
* field of the delegate must be checked.
*/
if (dg)
{
if (tf.isreturn)
e.e1.accept(this);
}
}
}
scope EscapeVisitor v = new EscapeVisitor(er);
e.accept(v);
}
/****************************************
* e is an expression to be returned by 'ref'.
* Walk e to determine which variables are possibly being
* returned by ref, such as:
* ref int function(int i) { return i; }
* If e is a form of *p, determine which variables have content
* which is being returned as ref, such as:
* ref int function(int* p) { return *p; }
* Multiple variables can be inserted, because of expressions like this:
* ref int function(bool b, int i, int* p) { return b ? i : *p; }
*
* No side effects.
*
* Params:
* e = expression to be returned by 'ref'
* er = where to place collected data
*/
private void escapeByRef(Expression e, EscapeByResults* er)
{
//printf("[%s] escapeByRef, e: %s\n", e.loc.toChars(), e.toChars());
extern (C++) final class EscapeRefVisitor : Visitor
{
alias visit = super.visit;
public: