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implemented large parts of the 'not nil' checking

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This commit is contained in:
Araq 2013-06-09 23:29:43 +02:00
commit 23ef565a3c
21 changed files with 290 additions and 109 deletions
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68
compiler/sempass2.nim
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@ -9,7 +9,7 @@
import
intsets, ast, astalgo, msgs, renderer, magicsys, types, idents, trees,
wordrecg, strutils, options
wordrecg, strutils, options, guards
# Second semantic checking pass over the AST. Necessary because the old
# way had some inherent problems. Performs:
@ -75,7 +75,7 @@ type
owner: PSym
init: seq[int] # list of initialized variables
# coming soon: "guard" tracking for 'let' variables
guards: TModel # nested guards
PEffects = var TEffects
proc isLocalVar(a: PEffects, s: PSym): bool =
@ -93,11 +93,14 @@ proc useVar(a: PEffects, n: PNode) =
let s = n.sym
if isLocalVar(a, s):
if s.id notin a.init:
if true:
Message(n.info, warnUninit, s.name.s)
if tfNeedsInit in s.typ.flags:
when true:
Message(n.info, warnProveInit, s.name.s)
else:
Message(n.info, errGenerated,
"'$1' might not have been initialized" % s.name.s)
else:
Message(n.info, errGenerated,
"read from potentially uninitialized variable: '$1'" % s.name.s)
Message(n.info, warnUninit, s.name.s)
# prevent superfluous warnings about the same variable:
a.init.add s.id
@ -295,7 +298,7 @@ proc propagateEffects(tracked: PEffects, n: PNode, s: PSym) =
let tagSpec = effectSpec(pragma, wTags)
mergeTags(tracked, tagSpec, n)
proc trackOperand(tracked: PEffects, n: PNode) =
proc trackOperand(tracked: PEffects, n: PNode, paramType: PType) =
let op = n.typ
if op != nil and op.kind == tyProc and n.kind != nkNilLit:
InternalAssert op.n.sons[0].kind == nkEffectList
@ -312,16 +315,40 @@ proc trackOperand(tracked: PEffects, n: PNode) =
else:
mergeEffects(tracked, effectList.sons[exceptionEffects], n)
mergeTags(tracked, effectList.sons[tagEffects], n)
if paramType != nil and tfNotNil in paramType.flags and
op != nil and tfNotNil notin op.flags:
case impliesNotNil(tracked.guards, n)
of impUnknown:
Message(n.info, errGenerated,
"cannot prove '$1' is not nil" % n.renderTree)
of impNo:
Message(n.info, errGenerated, "'$1' is provably nil" % n.renderTree)
of impYes: discard
proc breaksBlock(n: PNode): bool =
case n.kind
of nkStmtList, nkStmtListExpr:
for c in n:
if breaksBlock(c): return true
of nkBreakStmt, nkReturnStmt, nkRaiseStmt:
return true
of nkCallKinds:
if n.sons[0].kind == nkSym and sfNoReturn in n.sons[0].sym.flags:
return true
else:
discard
proc trackCase(tracked: PEffects, n: PNode) =
track(tracked, n.sons[0])
let oldState = tracked.init.len
var inter: TIntersection = @[]
var toCover = 0
for i in 1.. <n.len:
let branch = n.sons[i]
setLen(tracked.init, oldState)
for i in 0 .. <branch.len:
track(tracked, branch.sons[i])
if not breaksBlock(branch.lastSon): inc toCover
for i in oldState.. <tracked.init.len:
addToIntersection(inter, tracked.init[i])
let exh = case skipTypes(n.sons[0].Typ, abstractVarRange-{tyTypeDesc}).Kind
@ -332,30 +359,41 @@ proc trackCase(tracked: PEffects, n: PNode) =
setLen(tracked.init, oldState)
if exh:
for id, count in items(inter):
if count == n.len-1: tracked.init.add id
if count >= toCover: tracked.init.add id
# else we can't merge
proc trackIf(tracked: PEffects, n: PNode) =
track(tracked, n.sons[0].sons[0])
let oldFacts = tracked.guards.len
addFact(tracked.guards, n.sons[0].sons[0])
let oldState = tracked.init.len
var inter: TIntersection = @[]
var toCover = 0
track(tracked, n.sons[0].sons[1])
if not breaksBlock(n.sons[0].sons[1]): inc toCover
for i in oldState.. <tracked.init.len:
addToIntersection(inter, tracked.init[i])
for i in 1.. <n.len:
let branch = n.sons[i]
setLen(tracked.guards, oldFacts)
for j in 0..i-1:
addFactNeg(tracked.guards, n.sons[j].sons[0])
if branch.len > 1:
addFact(tracked.guards, branch.sons[0])
setLen(tracked.init, oldState)
for i in 0 .. <branch.len:
track(tracked, branch.sons[i])
if not breaksBlock(branch.lastSon): inc toCover
for i in oldState.. <tracked.init.len:
addToIntersection(inter, tracked.init[i])
setLen(tracked.init, oldState)
if lastSon(n).len == 1:
for id, count in items(inter):
if count == n.len: tracked.init.add id
if count >= toCover: tracked.init.add id
# else we can't merge as it is not exhaustive
setLen(tracked.guards, oldFacts)
proc trackBlock(tracked: PEffects, n: PNode) =
if n.kind in {nkStmtList, nkStmtListExpr}:
@ -377,6 +415,9 @@ proc isTrue(n: PNode): bool =
n.kind == nkSym and n.sym.kind == skEnumField and n.sym.position != 0 or
n.kind == nkIntLit and n.intVal != 0
proc paramType(op: PType, i: int): PType =
if op != nil and i < op.len: result = op.sons[i]
proc track(tracked: PEffects, n: PNode) =
case n.kind
of nkSym:
@ -404,11 +445,12 @@ proc track(tracked: PEffects, n: PNode) =
else:
mergeEffects(tracked, effectList.sons[exceptionEffects], n)
mergeTags(tracked, effectList.sons[tagEffects], n)
for i in 1 .. <len(n): trackOperand(tracked, n.sons[i])
for i in 1 .. <len(n): trackOperand(tracked, n.sons[i], paramType(op, i))
if a.kind == nkSym and a.sym.magic in {mNew, mNewFinalize,
mNewSeq, mShallowCopy}:
# may not look like an assignment, but it is:
initVar(tracked, n.sons[1])
# XXX new(objWithNotNil) is not initialized properly!
for i in 0 .. <safeLen(n):
track(tracked, n.sons[i])
of nkTryStmt: trackTryStmt(tracked, n)
@ -510,8 +552,14 @@ proc trackProc*(s: PSym, body: PNode) =
t.tags = effects.sons[tagEffects]
t.owner = s
t.init = @[]
t.guards = @[]
track(t, body)
if not isEmptyType(s.typ.sons[0]) and tfNeedsInit in s.typ.sons[0].flags and
s.kind in {skProc, skConverter, skMethod}:
var res = s.ast.sons[resultPos].sym # get result symbol
if res.id notin t.init:
Message(body.info, warnProveInit, "result")
let p = s.ast.sons[pragmasPos]
let raisesSpec = effectSpec(p, wRaises)
if not isNil(raisesSpec):