dmd.escape

struct EscapeState;

Groups global state for escape checking together

static void reset();

Called by initDMD / deinitializeDMD to reset global state

bool checkMutableArguments(ref Scope sc, FuncDeclaration fd, TypeFunction tf, Expression ethis, Expressions* arguments, bool gag);

Checks memory objects passed to a function. Checks that if a memory object is passed by ref or by pointer, all of the refs or pointers are const, or there is only one mutable ref or pointer to it.

References DIP 1021

Parameters:

Scope sc	used to determine current function and module
FuncDeclaration fd	function being called
TypeFunction tf	fd's type
Expression ethis	if not null, the this pointer
Expressions* arguments	actual arguments to function
bool gag	do not print error messages

Returns:

true if error

bool checkArrayLiteralEscape(ref Scope sc, ArrayLiteralExp ae, bool gag);

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.

Parameters:

Scope sc	used to determine current function and module
ArrayLiteralExp ae	array literal expression
bool gag	do not print error messages

Returns:

true if any elements escaped

bool checkAssocArrayLiteralEscape(ref Scope sc, AssocArrayLiteralExp ae, bool gag);

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.

Parameters:

Scope sc	used to determine current function and module
AssocArrayLiteralExp ae	associative array literal expression
bool gag	do not print error messages

Returns:

true if any elements escaped

bool checkParamArgumentEscape(ref Scope sc, FuncDeclaration fdc, Identifier parId, VarDeclaration vPar, STC parStc, Expression arg, bool assertmsg, bool gag);

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.

Parameters:

Scope sc	used to determine current function and module
FuncDeclaration fdc	function being called, null if called indirectly
Identifier parId	name of function parameter for error messages
VarDeclaration vPar	VarDeclaration corresponding to par
STC parStc	storage classes of function parameter (may have added scope from pure)
Expression arg	initializer for param
bool assertmsg	true if the parameter is the msg argument to assert(bool, msg).
bool gag	do not print error messages

Returns:

true if pointers to the stack can escape via assignment

bool checkParamArgumentReturn(ref Scope sc, Expression firstArg, Expression arg, Parameter param, bool gag);

Function argument initializes a return parameter, and that parameter gets assigned to firstArg. Essentially, treat as firstArg = arg;

Parameters:

Scope sc	used to determine current function and module
Expression firstArg	ref argument through which arg may be assigned
Expression arg	initializer for parameter
Parameter param	parameter declaration corresponding to arg
bool gag	do not print error messages

Returns:

true if assignment to firstArg would cause an error

bool checkConstructorEscape(ref Scope sc, CallExp ce, bool gag);

Check struct constructor of the form s.this(args), by checking each return parameter to see if it gets assigned to s.

Parameters:

Scope sc	used to determine current function and module
CallExp ce	constructor call of the form s.this(args)
bool gag	do not print error messages

Returns:

true if construction would cause an escaping reference error

enum ReturnParamDest: int;

How a return parameter escapes its pointer value

returnVal

through return statement: return x

this_

assigned to a struct instance: this.x = x

firstArg

assigned to first argument: firstArg = x

ReturnParamDest returnParamDest(TypeFunction tf, Type tthis);

Find out if instead of returning a return parameter via a return statement, it is returned via assignment to either this or the first parameter.

This works the same as returning the value via a return statement. Although the first argument must be ref, it is not regarded as returning by ref.

See Also:

https://dlang.org.spec/function.html#return-ref-parameters

Parameters:

TypeFunction tf	function type
Type tthis	type of this parameter, or null if none

Returns:

What a return parameter should transfer the lifetime of the argument to

bool checkAssignEscape(ref Scope sc, Expression e, bool gag, bool byRef);

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 attribute for the lvalue where possible, in order to eliminate the error.

Parameters:

Scope sc	used to determine current function and module
Expression e	AssignExp or CatAssignExp to check for any pointers to the stack
bool gag	do not print error messages
bool byRef	set to true if e1 of e gets assigned a reference to e2

Returns:

true if pointers to the stack can escape via assignment

bool checkThrowEscape(ref Scope sc, Expression e, bool gag);

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.

Parameters:

Scope sc	used to determine current function and module
Expression e	expression to check for any pointers to the stack
bool gag	do not print error messages

Returns:

true if pointers to the stack can escape

bool checkNewEscape(ref Scope sc, Expression e, bool gag);

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.

Parameters:

Scope sc	used to determine current function and module
Expression e	expression to check for any pointers to the stack
bool gag	do not print error messages

Returns:

true if pointers to the stack can escape

bool checkReturnEscape(ref Scope sc, Expression e, bool gag);

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.

Parameters:

Scope sc	used to determine current function and module
Expression e	expression to check for any pointers to the stack
bool gag	do not print error messages

Returns:

true if pointers to the stack can escape

bool checkReturnEscapeRef(ref Scope sc, Expression e, bool 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.

Parameters:

Scope sc	used to determine current function and module
Expression e	expression to check
bool gag	do not print error messages

Returns:

true if references to the stack can escape

void escapeByValue(Expression e, ref scope EscapeByResults er, bool retRefTransition = false);

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.

Parameters:

Expression e	expression to be returned by value
EscapeByResults er	where to place collected data
bool retRefTransition	if e is returned through a return (ref) scope function call

struct EscapeByResults;

Aggregate the data collected by the escapeBy??() functions.

void delegate(VarDeclaration, bool retRefTransition) byRef;

called on variables being returned by ref / address

void delegate(VarDeclaration) byValue;

called on variables with values containing pointers

void delegate(FuncDeclaration, bool called) byFunc;

called on nested functions that are turned into delegates When called is true, it means the delegate escapes variables from the closure through a call to it, while false means the delegate itself escapes.

void delegate(Expression, bool retRefTransition) byExp;

called when expression temporaries are being returned by ref / address

bool live;

if @live semantics apply, i.e. expressions p, *p, **p, etc., all return p.

void findAllOuterAccessedVariables(FuncDeclaration fd, VarDeclarations* vars);

Find all variables accessed by this delegate that are in functions enclosing it.

Parameters:

FuncDeclaration fd	function
VarDeclarations* vars	array to append found variables to

void finishScopeParamInference(FuncDeclaration funcdecl, ref TypeFunction f);

After semantic analysis of the function body, try to infer scope / return on the parameters

Parameters:

FuncDeclaration funcdecl	function declaration that was analyzed
TypeFunction f	final function type. funcdecl.type started as the 'premature type' before attribute inference, then its inferred attributes are copied over to final type f