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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) 1999-2018 by The D Language Foundation, 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: $(LINK2 https://github.com/dlang/dmd/blob/master/src/dmd/escape.d, _escape.d)
* Documentation: https://dlang.org/phobos/dmd_escape.html
* Coverage: https://codecov.io/gh/dlang/dmd/src/master/src/dmd/escape.d
*/
module dmd.escape;
import core.stdc.stdio : printf;
import dmd.aggregate;
import dmd.declaration;
import dmd.dscope;
import dmd.dsymbol;
import dmd.errors;
import dmd.expression;
import dmd.func;
import dmd.globals;
import dmd.identifier;
import dmd.init;
import dmd.mtype;
import dmd.root.rootobject;
import dmd.tokens;
import dmd.visitor;
import dmd.arraytypes;
/******************************************
* Array literal is going to be allocated on the GC heap.
* Check its elements to see if any would escape by going on the heap.
* Params:
* sc = used to determine current function and module
* ae = array literal expression
* gag = do not print error messages
* Returns:
* true if any elements escaped
*/
bool checkArrayLiteralEscape(Scope *sc, ArrayLiteralExp ae, bool gag)
{
bool errors;
if (ae.basis)
errors = checkNewEscape(sc, ae.basis, gag);
foreach (ex; *ae.elements)
{
if (ex)
errors |= checkNewEscape(sc, ex, gag);
}
return errors;
}
/******************************************
* Associative array literal is going to be allocated on the GC heap.
* Check its elements to see if any would escape by going on the heap.
* Params:
* sc = used to determine current function and module
* ae = associative array literal expression
* gag = do not print error messages
* Returns:
* true if any elements escaped
*/
bool checkAssocArrayLiteralEscape(Scope *sc, AssocArrayLiteralExp ae, bool gag)
{
bool errors;
foreach (ex; *ae.keys)
{
if (ex)
errors |= checkNewEscape(sc, ex, gag);
}
foreach (ex; *ae.values)
{
if (ex)
errors |= checkNewEscape(sc, ex, gag);
}
return errors;
}
/****************************************
* 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
* fdc = function being called, `null` if called indirectly
* 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)
{
enum log = false;
if (log) printf("checkParamArgumentEscape(arg: %s par: %s)\n", arg ? arg.toChars() : "null", par ? par.toChars() : "null");
//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)
{
if (log) printf("byvalue %s\n", v.toChars());
if (v.isDataseg())
continue;
Dsymbol p = v.toParent2();
notMaybeScope(v);
if (v.isScope())
{
unsafeAssign(v, "scope variable");
}
else if (v.storage_class & STC.variadic && 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'.
*/
if (log) printf("no infer for %s in %s loc %s, fdc %s, %d\n",
v.toChars(), sc.func.ident.toChars(), sc.func.loc.toChars(), fdc.ident.toChars(), __LINE__);
v.doNotInferScope = true;
}
}
foreach (VarDeclaration v; er.byref)
{
if (log) printf("byref %s\n", v.toChars());
if (v.isDataseg())
continue;
Dsymbol p = v.toParent2();
notMaybeScope(v);
if ((v.storage_class & (STC.ref_ | STC.out_)) == 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();
notMaybeScope(v);
if ((v.storage_class & (STC.ref_ | STC.out_ | STC.scope_)) && 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
* e = AssignExp or CatAssignExp 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)
{
enum log = false;
if (log) printf("checkAssignEscape(e: %s)\n", e.toChars());
if (e.op != TOK.assign && e.op != TOK.blit && e.op != TOK.construct &&
e.op != TOK.concatenateAssign && e.op != TOK.concatenateElemAssign && e.op != TOK.concatenateDcharAssign)
return false;
auto ae = cast(BinExp)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 == TOK.slice)
return false;
EscapeByResults er;
escapeByValue(e2, &er);
if (!er.byref.dim && !er.byvalue.dim && !er.byfunc.dim && !er.byexp.dim)
return false;
VarDeclaration va = expToVariable(e1);
if (va && e.op == TOK.concatenateElemAssign)
{
/* https://issues.dlang.org/show_bug.cgi?id=17842
* Draw an equivalence between:
* *q = p;
* and:
* va ~= e;
* since we are not assigning to va, but are assigning indirectly through va.
*/
va = null;
}
if (va && e1.op == TOK.dotVariable && va.type.toBasetype().ty == Tclass)
{
/* https://issues.dlang.org/show_bug.cgi?id=17949
* Draw an equivalence between:
* *q = p;
* and:
* va.field = e2;
* since we are not assigning to va, but are assigning indirectly through class reference va.
*/
va = null;
}
if (log && va) printf("va: %s\n", va.toChars());
// 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 != TRUST.system;
//printf("inferScope = %d, %d\n", inferScope, (va.storage_class & STCmaybescope) != 0);
// Determine if va is a parameter that is an indirect reference
const bool vaIsRef = va && va.storage_class & STC.parameter &&
(va.storage_class & (STC.ref_ | STC.out_) || va.type.toBasetype().ty == Tclass);
bool result = false;
foreach (VarDeclaration v; er.byvalue)
{
if (log) printf("byvalue: %s\n", v.toChars());
if (v.isDataseg())
continue;
if (v == va)
continue;
Dsymbol p = v.toParent2();
if (va && !vaIsRef && !va.isScope() && !v.isScope() &&
(va.storage_class & v.storage_class & (STC.maybescope | STC.variadic)) == STC.maybescope &&
p == sc.func)
{
/* Add v to va's list of dependencies
*/
va.addMaybe(v);
continue;
}
if (!(va && va.isScope()) || vaIsRef)
notMaybeScope(v);
if (v.isScope())
{
if (va && va.isScope() && va.storage_class & STC.return_ && !(v.storage_class & STC.return_) &&
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 & (STC.parameter | STC.temp)) ||
// va is class reference
ae.e1.op == TOK.dotVariable && va.type.toBasetype().ty == Tclass && (va.enclosesLifetimeOf(v) || !va.isScope()) ||
vaIsRef ||
va.storage_class & (STC.ref_ | STC.out_) && !(v.storage_class & STC.temp)) &&
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 |= STC.scope_ | STC.scopeinferred;
va.storage_class |= v.storage_class & STC.return_;
}
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 & STC.variadic && 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 |= STC.scope_ | STC.scopeinferred;
}
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'.
*/
//printf("no infer for %s in %s, %d\n", v.toChars(), sc.func.ident.toChars(), __LINE__);
v.doNotInferScope = true;
}
}
ByRef:
foreach (VarDeclaration v; er.byref)
{
if (log) 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 & STC.parameter) ||
va.storage_class & STC.ref_ ||
va.isDataseg()) &&
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 && v.storage_class & (STC.ref_ | STC.out_))
{
Dsymbol pva = va.toParent2();
for (Dsymbol pv = p; pv; )
{
pv = pv.toParent2();
if (pva == pv) // if v is nested inside pva
{
if (sc.func.setUnsafe())
{
if (!gag)
error(ae.loc, "reference `%s` assigned to `%s` with longer lifetime", v.toChars(), va.toChars());
result = true;
continue ByRef;
}
break;
}
}
}
if (!(va && va.isScope()))
notMaybeScope(v);
if ((v.storage_class & (STC.ref_ | STC.out_)) == 0 && p == sc.func)
{
if (va && !va.isDataseg() && !va.doNotInferScope)
{
if (!va.isScope() && inferScope)
{ //printf("inferring scope for %s\n", va.toChars());
va.storage_class |= STC.scope_ | STC.scopeinferred;
}
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)
{
if (log) printf("byfunc: %s, %d\n", fd.toChars(), fd.tookAddressOf);
VarDeclarations vars;
findAllOuterAccessedVariables(fd, &vars);
/* https://issues.dlang.org/show_bug.cgi?id=16037
* If assigning the address of a delegate to a scope variable,
* then uncount that address of. This is so it won't cause a
* closure to be allocated.
*/
if (va && va.isScope() && fd.tookAddressOf && global.params.vsafe)
--fd.tookAddressOf;
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()))
notMaybeScope(v);
if ((v.storage_class & (STC.ref_ | STC.out_ | STC.scope_)) && p == sc.func)
{
if (va && !va.isDataseg() && !va.doNotInferScope)
{
/* Don't infer STC.scope_ for va, because then a closure
* won't be generated for sc.func.
*/
//if (!va.isScope() && inferScope)
//va.storage_class |= STC.scope_ | STC.scopeinferred;
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 (log) printf("byexp: %s\n", ee.toChars());
/* Do not allow slicing of a static array returned by a function
*/
if (va && ee.op == TOK.call && ee.type.toBasetype().ty == Tsarray && va.type.toBasetype().ty == Tarray &&
!(va.storage_class & STC.temp))
{
if (!gag)
deprecation(ee.loc, "slice of static array temporary returned by `%s` assigned to longer lived variable `%s`",
ee.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 |= STC.scope_ | STC.scopeinferred;
}
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;
if (v.isScope() && !v.iscatchvar) // special case: allow catch var to be rethrown
// despite being `scope`
{
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 in %s, %d\n", v.toChars(), sc.func.ident.toChars(), __LINE__);
v.doNotInferScope = true;
}
}
return result;
}
/************************************
* Detect cases where pointers to the stack can 'escape' the
* lifetime of the stack frame by being placed into a GC allocated object.
* 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 checkNewEscape(Scope* sc, Expression e, bool gag)
{
//printf("[%s] checkNewEscape, e = %s\n", e.loc.toChars(), e.toChars());
enum log = false;
if (log) printf("[%s] checkNewEscape, 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)
{
if (log) printf("byvalue `%s`\n", v.toChars());
if (v.isDataseg())
continue;
Dsymbol p = v.toParent2();
if (v.isScope())
{
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; }
*/
!(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 copied into allocated memory", v.toChars());
result = true;
}
continue;
}
}
else if (v.storage_class & STC.variadic && p == sc.func)
{
Type tb = v.type.toBasetype();
if (tb.ty == Tarray || tb.ty == Tsarray)
{
if (!gag)
error(e.loc, "copying `%s` into allocated memory escapes a reference to variadic parameter `%s`", e.toChars(), v.toChars());
result = false;
}
}
else
{
//printf("no infer for %s in %s, %d\n", v.toChars(), sc.func.ident.toChars(), __LINE__);
v.doNotInferScope = true;
}
}
foreach (VarDeclaration v; er.byref)
{
if (log) printf("byref `%s`\n", v.toChars());
void escapingRef(VarDeclaration v)
{
if (!gag)
{
const(char)* kind = (v.storage_class & STC.parameter) ? "parameter" : "local";
error(e.loc, "copying `%s` into allocated memory escapes a reference to %s variable `%s`",
e.toChars(), kind, v.toChars());
}
result = true;
}
if (v.isDataseg())
continue;
Dsymbol p = v.toParent2();
if ((v.storage_class & (STC.ref_ | STC.out_)) == 0)
{
if (p == sc.func)
{
escapingRef(v);
continue;
}
}
/* 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 & (STC.ref_ | STC.out_))
{
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);
escapingRef(v);
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, "storing reference to outer local variable `%s` into allocated memory causes it to escape",
v.toChars());
result = true;
continue;
}
}
}
}
}
foreach (Expression ee; er.byexp)
{
if (log) printf("byexp %s\n", ee.toChars());
if (!gag)
error(ee.loc, "storing reference to stack allocated value returned by `%s` into allocated memory causes it to escape",
ee.toChars());
result = 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);
}
/***************************************
* Implementation of checking for escapes in `return`.
* 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
*/
private bool checkReturnEscapeImpl(Scope* sc, Expression e, bool refs, bool gag)
{
enum log = false;
if (log) printf("[%s] checkReturnEscapeImpl, refs: %d e: `%s`\n", e.loc.toChars(), refs, 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)
{
if (log) printf("byvalue `%s`\n", v.toChars());
if (v.isDataseg())
continue;
Dsymbol p = v.toParent2();
if ((v.isScope() || (v.storage_class & STC.maybescope)) &&
!(v.storage_class & STC.return_) &&
v.isParameter() &&
sc.func.flags & FUNCFLAG.returnInprocess &&
p == sc.func)
{
inferReturn(sc.func, v); // infer addition of 'return'
continue;
}
if (v.isScope())
{
if (v.storage_class & STC.return_)
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 & STC.variadic && p == sc.func)
{
Type tb = v.type.toBasetype();
if (tb.ty == Tarray || tb.ty == Tsarray)
{
if (!gag)
error(e.loc, "returning `%s` escapes a reference to variadic parameter `%s`", e.toChars(), v.toChars());
result = false;
}
}
else
{
//printf("no infer for %s in %s, %d\n", v.toChars(), sc.func.ident.toChars(), __LINE__);
v.doNotInferScope = true;
}
}
foreach (VarDeclaration v; er.byref)
{
if (log) printf("byref `%s`\n", v.toChars());
void escapingRef(VarDeclaration v)
{
if (!gag)
{
const(char)* msg;
if (v.storage_class & STC.parameter)
msg = "returning `%s` escapes a reference to parameter `%s`, perhaps annotate with `return`";
else
msg = "returning `%s` escapes a reference to local variable `%s`";
error(e.loc, msg, e.toChars(), v.toChars());
}
result = true;
}
if (v.isDataseg())
continue;
Dsymbol p = v.toParent2();
if ((v.storage_class & (STC.ref_ | STC.out_)) == 0)
{
if (p == sc.func)
{
escapingRef(v);
continue;
}
FuncDeclaration fd = p.isFuncDeclaration();
if (fd && sc.func.flags & FUNCFLAG.returnInprocess)
{
/* 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 |= STC.return_;
}
}
/* 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 & (STC.ref_ | STC.out_)) &&
!(v.storage_class & (STC.return_ | STC.foreach_)))
{
if (sc.func.flags & FUNCFLAG.returnInprocess && 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);
escapingRef(v);
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)
{
if (log) 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 STC.return_
*/
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 |= STC.return_;
TypeFunction tf = cast(TypeFunction)fd.type;
if (v == fd.vthis)
{
/* v is the 'this' reference, so mark the function
*/
fd.storage_class |= STC.return_;
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);