diff options
| -rw-r--r-- | compiler/vm.nim | 257 | ||||
| -rw-r--r-- | compiler/vmgen.nim | 24 | ||||
| -rw-r--r-- | tests/exception/texceptions.nim | 51 | ||||
| -rw-r--r-- | tests/vm/tmisc_vm.nim | 20 |
4 files changed, 242 insertions, 110 deletions
diff --git a/compiler/vm.nim b/compiler/vm.nim index 71fd2722b..f855da0cc 100644 --- a/compiler/vm.nim +++ b/compiler/vm.nim @@ -23,7 +23,7 @@ from evaltempl import evalTemplate from modulegraphs import ModuleGraph, PPassContext const - traceCode = debugEchoCode + traceCode = defined(nimVMDebug) when hasFFI: import evalffi @@ -259,64 +259,101 @@ proc pushSafePoint(f: PStackFrame; pc: int) = f.safePoints.add(pc) proc popSafePoint(f: PStackFrame) = - # XXX this needs a proper fix! - if f.safePoints.len > 0: - discard f.safePoints.pop() - -proc cleanUpOnException(c: PCtx; tos: PStackFrame): - tuple[pc: int, f: PStackFrame] = - let raisedType = c.currentExceptionA.typ.skipTypes(abstractPtrs) - var f = tos - while true: - while f.safePoints.len == 0: - f = f.next - if f.isNil: return (-1, nil) - var pc2 = f.safePoints[f.safePoints.high] - - var nextExceptOrFinally = -1 - if c.code[pc2].opcode == opcExcept: - nextExceptOrFinally = pc2 + c.code[pc2].regBx - wordExcess - inc pc2 - while c.code[pc2].opcode == opcExcept: - let excIndex = c.code[pc2].regBx-wordExcess - let exceptType = if excIndex > 0: c.types[excIndex].skipTypes( - abstractPtrs) - else: nil - #echo typeToString(exceptType), " ", typeToString(raisedType) - if exceptType.isNil or inheritanceDiff(raisedType, exceptType) <= 0: - # mark exception as handled but keep it in B for - # the getCurrentException() builtin: - c.currentExceptionB = c.currentExceptionA - c.currentExceptionA = nil - # execute the corresponding handler: - while c.code[pc2].opcode == opcExcept: inc pc2 - discard f.safePoints.pop - return (pc2, f) - inc pc2 - if c.code[pc2].opcode != opcExcept and nextExceptOrFinally >= 0: - # we're at the end of the *except list*, but maybe there is another - # *except branch*? - pc2 = nextExceptOrFinally+1 - if c.code[pc2].opcode == opcExcept: - nextExceptOrFinally = pc2 + c.code[pc2].regBx - wordExcess - - if nextExceptOrFinally >= 0: - pc2 = nextExceptOrFinally - if c.code[pc2].opcode == opcFinally: - # execute the corresponding handler, but don't quit walking the stack: - discard f.safePoints.pop - return (pc2+1, f) - # not the right one: - discard f.safePoints.pop + discard f.safePoints.pop() + +type + ExceptionGoto = enum + ExceptionGotoHandler, + ExceptionGotoFinally, + ExceptionGotoUnhandled + +proc findExceptionHandler(c: PCtx, f: PStackFrame, exc: PNode): + tuple[why: ExceptionGoto, where: int] = + let raisedType = exc.typ.skipTypes(abstractPtrs) + + while f.safePoints.len > 0: + var pc = f.safePoints.pop() + + var matched = false + var pcEndExcept = pc + + # Scan the chain of exceptions starting at pc. + # The structure is the following: + # pc - opcExcept, <end of this block> + # - opcExcept, <pattern1> + # - opcExcept, <pattern2> + # ... + # - opcExcept, <patternN> + # - Exception handler body + # - ... more opcExcept blocks may follow + # - ... an optional opcFinally block may follow + # + # Note that the exception handler body already contains a jump to the + # finally block or, if that's not present, to the point where the execution + # should continue. + # Also note that opcFinally blocks are the last in the chain. + while c.code[pc].opcode == opcExcept: + # Where this Except block ends + pcEndExcept = pc + c.code[pc].regBx - wordExcess + inc pc + + # A series of opcExcept follows for each exception type matched + while c.code[pc].opcode == opcExcept: + let excIndex = c.code[pc].regBx - wordExcess + let exceptType = + if excIndex > 0: c.types[excIndex].skipTypes(abstractPtrs) + else: nil + + # echo typeToString(exceptType), " ", typeToString(raisedType) + + # Determine if the exception type matches the pattern + if exceptType.isNil or inheritanceDiff(raisedType, exceptType) <= 0: + matched = true + break + + inc pc + + # Skip any further ``except`` pattern and find the first instruction of + # the handler body + while c.code[pc].opcode == opcExcept: + inc pc + + if matched: + break + + # If no handler in this chain is able to catch this exception we check if + # the "parent" chains are able to. If this chain ends with a `finally` + # block we must execute it before continuing. + pc = pcEndExcept + + # Where the handler body starts + let pcBody = pc + + if matched: + return (ExceptionGotoHandler, pcBody) + elif c.code[pc].opcode == opcFinally: + # The +1 here is here because we don't want to execute it since we've + # already pop'd this statepoint from the stack. + return (ExceptionGotoFinally, pc + 1) + + return (ExceptionGotoUnhandled, 0) proc cleanUpOnReturn(c: PCtx; f: PStackFrame): int = - for s in f.safePoints: - var pc = s + # Walk up the chain of safepoints and return the PC of the first `finally` + # block we find or -1 if no such block is found. + # Note that the safepoint is removed once the function returns! + result = -1 + + # Traverse the stack starting from the end in order to execute the blocks in + # the inteded order + for i in 1 .. f.safePoints.len: + var pc = f.safePoints[^i] + # Skip the `except` blocks while c.code[pc].opcode == opcExcept: - pc = pc + c.code[pc].regBx - wordExcess + pc += c.code[pc].regBx - wordExcess if c.code[pc].opcode == opcFinally: - return pc - return -1 + discard f.safePoints.pop + return pc + 1 proc opConv(c: PCtx; dest: var TFullReg, src: TFullReg, desttyp, srctyp: PType): bool = if desttyp.kind == tyString: @@ -449,6 +486,9 @@ const proc rawExecute(c: PCtx, start: int, tos: PStackFrame): TFullReg = var pc = start var tos = tos + # Used to keep track of where the execution is resumed. + var savedPC = -1 + var savedFrame: PStackFrame var regs: seq[TFullReg] # alias to tos.slots for performance move(regs, tos.slots) #echo "NEW RUN ------------------------" @@ -456,27 +496,31 @@ proc rawExecute(c: PCtx, start: int, tos: PStackFrame): TFullReg = #{.computedGoto.} let instr = c.code[pc] let ra = instr.regA - #if c.traceActive: + when traceCode: echo "PC ", pc, " ", c.code[pc].opcode, " ra ", ra, " rb ", instr.regB, " rc ", instr.regC - # message(c.config, c.debug[pc], warnUser, "Trace") case instr.opcode of opcEof: return regs[ra] of opcRet: - # XXX perform any cleanup actions - pc = tos.comesFrom - tos = tos.next - let retVal = regs[0] - if tos.isNil: - #echo "RET ", retVal.rendertree - return retVal - - move(regs, tos.slots) - assert c.code[pc].opcode in {opcIndCall, opcIndCallAsgn} - if c.code[pc].opcode == opcIndCallAsgn: - regs[c.code[pc].regA] = retVal - #echo "RET2 ", retVal.rendertree, " ", c.code[pc].regA + let newPc = c.cleanUpOnReturn(tos) + # Perform any cleanup action before returning + if newPc < 0: + pc = tos.comesFrom + tos = tos.next + let retVal = regs[0] + if tos.isNil: + return retVal + + move(regs, tos.slots) + assert c.code[pc].opcode in {opcIndCall, opcIndCallAsgn} + if c.code[pc].opcode == opcIndCallAsgn: + regs[c.code[pc].regA] = retVal + else: + savedPC = pc + savedFrame = tos + # The -1 is needed because at the end of the loop we increment `pc` + pc = newPc - 1 of opcYldYoid: assert false of opcYldVal: assert false of opcAsgnInt: @@ -1025,7 +1069,7 @@ proc rawExecute(c: PCtx, start: int, tos: PStackFrame): TFullReg = # it's a callback: c.callbacks[-prc.offset-2].value( VmArgs(ra: ra, rb: rb, rc: rc, slots: cast[pointer](regs), - currentException: c.currentExceptionB, + currentException: c.currentExceptionA, currentLineInfo: c.debug[pc])) elif sfImportc in prc.flags: if allowFFI notin c.features: @@ -1118,44 +1162,55 @@ proc rawExecute(c: PCtx, start: int, tos: PStackFrame): TFullReg = tos.pushSafePoint(pc + rbx) assert c.code[pc+rbx].opcode in {opcExcept, opcFinally} of opcExcept: - # just skip it; it's followed by a jump; - # we'll execute in the 'raise' handler - let rbx = instr.regBx - wordExcess - 1 # -1 for the following 'inc pc' - inc pc, rbx - while c.code[pc+1].opcode == opcExcept: - let rbx = c.code[pc+1].regBx - wordExcess - 1 - inc pc, rbx - #assert c.code[pc+1].opcode in {opcExcept, opcFinally} - if c.code[pc+1].opcode != opcFinally: - # in an except handler there is no active safe point for the 'try': - tos.popSafePoint() + # This opcode is never executed, it only holds informations for the + # exception handling routines. + doAssert(false) of opcFinally: - # just skip it; it's followed by the code we need to execute anyway + # Pop the last safepoint introduced by a opcTry. This opcode is only + # executed _iff_ no exception was raised in the body of the `try` + # statement hence the need to pop the safepoint here. + doAssert(savedPC < 0) tos.popSafePoint() of opcFinallyEnd: - if c.currentExceptionA != nil: - # we are in a cleanup run: - let (newPc, newTos) = cleanUpOnException(c, tos) - if newPc-1 < 0: - bailOut(c, tos) - return - pc = newPc-1 - if tos != newTos: - tos = newTos + # The control flow may not resume at the next instruction since we may be + # raising an exception or performing a cleanup. + if not savedPC < 0: + pc = savedPC - 1 + savedPC = -1 + if tos != savedFrame: + tos = savedFrame move(regs, tos.slots) of opcRaise: let raised = regs[ra].node c.currentExceptionA = raised c.exceptionInstr = pc - let (newPc, newTos) = cleanUpOnException(c, tos) - # -1 because of the following 'inc' - if newPc-1 < 0: + + var frame = tos + var jumpTo = findExceptionHandler(c, frame, raised) + while jumpTo.why == ExceptionGotoUnhandled and not frame.next.isNil: + frame = frame.next + jumpTo = findExceptionHandler(c, frame, raised) + + case jumpTo.why: + of ExceptionGotoHandler: + # Jump to the handler, do nothing when the `finally` block ends. + savedPC = -1 + pc = jumpTo.where - 1 + if tos != frame: + tos = frame + move(regs, tos.slots) + of ExceptionGotoFinally: + # Jump to the `finally` block first then re-jump here to continue the + # traversal of the exception chain + savedPC = pc + savedFrame = tos + pc = jumpTo.where - 1 + if tos != frame: + tos = frame + move(regs, tos.slots) + of ExceptionGotoUnhandled: + # Nobody handled this exception, error out. bailOut(c, tos) - return - pc = newPc-1 - if tos != newTos: - tos = newTos - move(regs, tos.slots) of opcNew: ensureKind(rkNode) let typ = c.types[instr.regBx - wordExcess] @@ -1295,7 +1350,7 @@ proc rawExecute(c: PCtx, start: int, tos: PStackFrame): TFullReg = idx = int(regs[rb+rc-1].intVal) callback = c.callbacks[idx].value args = VmArgs(ra: ra, rb: rb, rc: rc, slots: cast[pointer](regs), - currentException: c.currentExceptionB, + currentException: c.currentExceptionA, currentLineInfo: c.debug[pc]) callback(args) regs[ra].node.flags.incl nfIsRef diff --git a/compiler/vmgen.nim b/compiler/vmgen.nim index f513c59a7..980901593 100644 --- a/compiler/vmgen.nim +++ b/compiler/vmgen.nim @@ -83,9 +83,12 @@ proc codeListing(c: PCtx, result: var string, start=0; last = -1) = elif opc < firstABxInstr: result.addf("\t$#\tr$#, r$#, r$#", opc.toStr, x.regA, x.regB, x.regC) - elif opc in relativeJumps: + elif opc in relativeJumps + {opcTry}: result.addf("\t$#\tr$#, L$#", opc.toStr, x.regA, i+x.regBx-wordExcess) + elif opc in {opcExcept}: + let idx = x.regBx-wordExcess + result.addf("\t$#\t$#, $#", opc.toStr, x.regA, $idx) elif opc in {opcLdConst, opcAsgnConst}: let idx = x.regBx-wordExcess result.addf("\t$#\tr$#, $# ($#)", opc.toStr, x.regA, @@ -480,10 +483,13 @@ proc genType(c: PCtx; typ: PType): int = proc genTry(c: PCtx; n: PNode; dest: var TDest) = if dest < 0 and not isEmptyType(n.typ): dest = getTemp(c, n.typ) var endings: seq[TPosition] = @[] - let elsePos = c.xjmp(n, opcTry, 0) + let ehPos = c.xjmp(n, opcTry, 0) c.gen(n.sons[0], dest) c.clearDest(n, dest) - c.patch(elsePos) + # Add a jump past the exception handling code + endings.add(c.xjmp(n, opcJmp, 0)) + # This signals where the body ends and where the exception handling begins + c.patch(ehPos) for i in 1 ..< n.len: let it = n.sons[i] if it.kind != nkFinally: @@ -499,14 +505,14 @@ proc genTry(c: PCtx; n: PNode; dest: var TDest) = c.gABx(it, opcExcept, 0, 0) c.gen(it.lastSon, dest) c.clearDest(n, dest) - if i < sonsLen(n)-1: + if i < sonsLen(n): endings.add(c.xjmp(it, opcJmp, 0)) c.patch(endExcept) - for endPos in endings: c.patch(endPos) let fin = lastSon(n) # we always generate an 'opcFinally' as that pops the safepoint - # from the stack + # from the stack if no exception is raised in the body. c.gABx(fin, opcFinally, 0, 0) + for endPos in endings: c.patch(endPos) if fin.kind == nkFinally: c.gen(fin.sons[0]) c.clearDest(n, dest) @@ -2214,9 +2220,9 @@ proc genProc(c: PCtx; s: PSym): int = c.gABC(body, opcEof, eofInstr.regA) c.optimizeJumps(result) s.offset = c.prc.maxSlots - #if s.name.s == "calc": - # echo renderTree(body) - # c.echoCode(result) + # if s.name.s == "fun1": + # echo renderTree(body) + # c.echoCode(result) c.prc = oldPrc else: c.prc.maxSlots = s.offset diff --git a/tests/exception/texceptions.nim b/tests/exception/texceptions.nim index d63187b0e..7bce32837 100644 --- a/tests/exception/texceptions.nim +++ b/tests/exception/texceptions.nim @@ -74,3 +74,54 @@ block: #10417 moo() doAssert(bar == 1) + +# Make sure the VM handles the exceptions correctly +block: + proc fun1(): seq[int] = + try: + try: + raise newException(ValueError, "xx") + except: + doAssert("xx" == getCurrentExceptionMsg()) + raise newException(KeyError, "yy") + except: + doAssert("yy" == getCurrentExceptionMsg()) + result.add(1212) + try: + try: + raise newException(AssertionError, "a") + finally: + result.add(42) + except AssertionError: + result.add(99) + finally: + result.add(10) + result.add(4) + result.add(0) + try: + result.add(1) + except KeyError: + result.add(-1) + except ValueError: + result.add(-1) + except IndexError: + result.add(2) + except: + result.add(3) + + try: + try: + result.add(1) + return + except: + result.add(-1) + finally: + result.add(2) + except KeyError: + doAssert(false) + finally: + result.add(3) + + let x1 = fun1() + const x2 = fun1() + doAssert(x1 == x2) diff --git a/tests/vm/tmisc_vm.nim b/tests/vm/tmisc_vm.nim index 6eb3dd627..bce0159ce 100644 --- a/tests/vm/tmisc_vm.nim +++ b/tests/vm/tmisc_vm.nim @@ -49,3 +49,23 @@ static: echo "caught Defect" except ValueError: echo "caught ValueError" + +# bug #10538 + +block: + proc fun1(): seq[int] = + try: + try: + result.add(1) + return + except: + result.add(-1) + finally: + result.add(2) + finally: + result.add(3) + result.add(4) + + let x1 = fun1() + const x2 = fun1() + doAssert(x1 == x2) |