dmd.ob
Flow analysis for Ownership/Borrowing
License
Source: ob.d
Documentation: https://dlang.org/phobos/dmd_escape.html
-
Declaration
void
oblive
(FuncDeclarationfuncdecl
);Perform ownership/borrowing checks for
funcdecl
. Does not modify the AST, just checks for errors. -
Declaration
struct
ObState
;Collect the state information.
-
Declaration
Array!size_t
varStack
;temporary storage
-
Declaration
Array!bool
mutableStack
;parallel to varStack[], is type mutable?
-
Declaration
PtrVarState[]
varPool
;memory pool
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-
Declaration
struct
ObNode
;A node in the function's expression graph, and its edges to predecessors and successors.
-
Declaration
Expression
exp
;expression for the node
-
Declaration
ObNodes
preds
;predecessors
-
Declaration
ObNodes
succs
;successors
-
Declaration
ObNode*
tryBlock
;try-finally block we're inside
-
Declaration
uint
index
;index
of this in obnodes -
Declaration
PtrVarState[]
gen
;new states generated for this node
-
Declaration
PtrVarState[]
input
;variable states on entry to exp
-
Declaration
PtrVarState[]
output
;variable states on exit to exp
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-
Declaration
enum
PtrState
: ubyte;Pointer variable states:
Discussion
Initial state is not known; ignore for now
Undefined not in a usable state
T* p = void;
Owner mutable pointer
T* p = initializer;
Borrowed scope mutable pointer, borrowed from [p]
T* p = initializer; scope T* b = p;
Readonly scope const pointer, copied from [p]
T* p = initializer; scope const(T)* cp = p;Examples
T* p = initializer; // p is owner T** pp = &p; // pp borrows from p
T* p = initialize; // p is owner T* q = p; // transfer: q is owner, p is undefined -
Declaration
const(char)*
toChars
(PtrStatestate
); -
Declaration
struct
PtrVarState
;Carries the state of a pointer variable.
-
Declaration
BitArray
deps
;dependencies
-
Declaration
PtrState
state
;state
the pointer variable is in -
Declaration
void
print
(VarDeclaration[]vars
); -
Declaration
void
depsToBuf
(ref OutBufferbuf
, const VarDeclaration[]vars
);Produce a user-readable comma separated string of the dependencies.
Parameters
OutBuffer
buf
write resulting string here
VarDeclaration[]
vars
array from which to get the variable names
-
-
Declaration
void
setLabelStatementExtraFields
(DsymbolTablelabtab
);Set the
.extra
field for LabelStatements inlabtab
[]. -
Declaration
void
toObNodes
(ref ObNodesobnodes
, Statements
);Convert statement into ObNodes.
-
Declaration
void
insertFinallyBlockCalls
(ref ObNodesobnodes
);Insert finally block calls when doing a goto from inside a try block to outside. Done after blocks are generated because then we know all the edges of the graph, but before the pred's are computed.
Parameters
ObNodes
obnodes
graph of the function
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Declaration
void
insertFinallyBlockGotos
(ref ObNodesobnodes
);Remove try-finally scaffolding.
Parameters
ObNodes
obnodes
nodes for the function
-
Declaration
void
numberNodes
(ref ObNodesobnodes
);Set the
index
field of each ObNode to its index in the
array.obnodes
[] -
Declaration
void
removeUnreachable
(ref ObNodesobnodes
);Remove unreachable nodes and compress them out of
obnodes
[].Parameters
ObNodes
obnodes
array of nodes
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Declaration
void
computePreds
(ref ObNodesobnodes
);Compute predecessors.
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Declaration
bool
isTrackableVar
(VarDeclarationv
);Are we interested in tracking variable
?v
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Declaration
VarDeclaration
isTrackableVarExp
(Expressione
);Are we interested in tracking this expression?
Return Value
variable if so,
null
if not -
Declaration
void
collectVars
(FuncDeclarationfuncdecl
, out VarDeclarationsvars
);Find the pointer variable declarations in this function, and fill
with them.vars
Parameters
FuncDeclaration
funcdecl
function we are in
VarDeclarations
vars
array to fill in
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Declaration
void
allocDeps
(PtrVarState[]pvss
);Allocate BitArrays in PtrVarState. Can be allocated much more efficiently by subdividing a single large array of bits
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Declaration
void
allocStates
(ref ObStateobstate
);Allocate state variables foreach node.
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Declaration
bool
isBorrowedPtr
(VarDeclarationv
);Does
v
meet the definiton of aBorrowed
pointer?Return Value
true
if it does -
Declaration
bool
isReadonlyPtr
(VarDeclarationv
);Does
v
meet the definiton of aReadonly
pointer?Return Value
true
if it does -
Declaration
void
genKill
(ref ObStateobstate
, ObNode*ob
);Compute the gen vector for
ob
. -
Declaration
PtrState
toPtrState
(VarDeclarationv
);Determine the state of a variable based on its type and storage class.
-
Declaration
bool
hasPointersToMutableFields
(Typet
);Does type
contain any pointers to mutable?t
-
Declaration
bool
hasMutableFields
(Typet
);Does type
have any mutable fields?t
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Declaration
void
doDataFlowAnalysis
(ref ObStateobstate
);Do the data flow analysis (i.e. compute the input[] and output[] vectors for each ObNode).
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Declaration
void
checkObErrors
(ref ObStateobstate
);Check for Ownership/Borrowing errors.
-
Declaration
void
readVar
(ObNode*ob
, const size_tvi
, boolmutable
, PtrVarState[]gen
);Read from variable
vi
. The beginning of the 'scope' of a variable is when it is first read. Hence, when a read is done, instead of when assignment to the variable is done, the O/B rules are enforced. (Also called "non-lexical scoping".) -
Declaration
void
makeChildrenUndefined
(size_tvi
, PtrVarState[]gen
);Recursively make Undefined all who list
vi
as a dependency -
Declaration
void
makeUndefined
(size_tvi
, PtrVarState[]gen
);Recursively make Undefined
vi
undefined and all who listvi
as a dependency -
Declaration
bool
isMutableRef
(Typet
);Is type
a reference to a const or a reference to a mutable?t