article/copyright.html


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		<title>Copyright: It's okay</title>
		<link rel="stylesheet" href="/style.css" />
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		<h1>Copyright: It's okay</h1>
		<p>Article ID: 6</p>
		<p>
		Copyright law isn't as broken as some think.
		</p>

		<p>
		Modern copyright law allows for things like nonfree software that don't respect privacy and other freedoms.  But as long as it conforms to the license agreement that users thereof agree to, it's the users' responsibility to read the license agreement carefully and to agree to or decline it based on what they've read.  We Free Software developers <em><strong>grant</strong> the users the four freedoms</em>, others can choose to do otherwise.
		</p>

		<p>
		Information unlike physical items can be copied with minimal cost, especially in the case of digital information, and thus the traditional private property argument of "this is theft and the author loses stuff" doesn't really apply.  However, information/data that an author creates shall be under the control of the author, it's ultimately what they create and is their private information.  The authors, not anyone else, should control how their information goes.  (Transferring this control to another entity is ultimately using their control to share or give away the same control, so that's no different.)
		</p>

		<p>
		There are some jurisdictions that don't allow publishing works into the public domain.  I believe that this needs improvement, as I don't see a reason to force an author to control the distribution of their work when the author themselves don't want to.  For instance, this Website is, when possible, in the public domain, but in juristictions like Germany where that's not possible, an alternative permissive license is used.
		</p>

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			<hr />
			<p><a href="/">Runxi Yu's Website</a></p>
			<p>Unless otherwise specified with the "<span class="copyright">copyright</span>" HTML/CSS class, works hosted on this subdomain (<code>www.andrewyu.org</code>) served with the HTTP(S) protocol is available under <a href="https://www.andrewyu.org/note/pubdom.html">Runxi Yu's Public Domain Dedication</a>.</p>
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#
#
#           The Nim Compiler
#        (c) Copyright 2015 Andreas Rumpf
#
#    See the file "copying.txt", included in this
#    distribution, for details about the copyright.
#

# included from cgen.nim

const
  RangeExpandLimit = 256      # do not generate ranges
                              # over 'RangeExpandLimit' elements
  stringCaseThreshold = 8
    # above X strings a hash-switch for strings is generated

proc getTraverseProc(p: BProc, v: PSym): Rope =
  if p.config.selectedGC in {gcMarkAndSweep, gcHooks, gcV2, gcRefc} and
      optOwnedRefs notin p.config.globalOptions and
      containsGarbageCollectedRef(v.loc.t):
    # we register a specialized marked proc here; this has the advantage
    # that it works out of the box for thread local storage then :-)
    result = genTraverseProcForGlobal(p.module, v, v.info)

proc registerTraverseProc(p: BProc, v: PSym, traverseProc: Rope) =
  if sfThread in v.flags:
    appcg(p.module, p.module.preInitProc.procSec(cpsInit),
      "$n\t#nimRegisterThreadLocalMarker($1);$n$n", [traverseProc])
  else:
    appcg(p.module, p.module.preInitProc.procSec(cpsInit),
      "$n\t#nimRegisterGlobalMarker($1);$n$n", [traverseProc])

proc isAssignedImmediately(conf: ConfigRef; n: PNode): bool {.inline.} =
  if n.kind == nkEmpty: return false
  if isInvalidReturnType(conf, n.typ):
    # var v = f()
    # is transformed into: var v;  f(addr v)
    # where 'f' **does not** initialize the result!
    return false
  result = true

proc inExceptBlockLen(p: BProc): int =
  for x in p.nestedTryStmts:
    if x.inExcept: result.inc

proc startBlockInternal(p: BProc): int {.discardable.} =
  inc(p.labels)
  result = p.blocks.len
  setLen(p.blocks, result + 1)
  p.blocks[result].id = p.labels
  p.blocks[result].nestedTryStmts = p.nestedTryStmts.len.int16
  p.blocks[result].nestedExceptStmts = p.inExceptBlockLen.int16

template startBlock(p: BProc, start: FormatStr = "{$n",
                args: varargs[Rope]): int =
  lineCg(p, cpsStmts, start, args)
  startBlockInternal(p)

proc endBlock(p: BProc)

proc genVarTuple(p: BProc, n: PNode) =
  var tup, field: TLoc
  if n.kind != nkVarTuple: internalError(p.config, n.info, "genVarTuple")

  # if we have a something that's been captured, use the lowering instead:
  for i in 0..<n.len-2:
    if n[i].kind != nkSym:
      genStmts(p, lowerTupleUnpacking(p.module.g.graph, n, p.module.idgen, p.prc))
      return

  # check only the first son
  var forHcr = treatGlobalDifferentlyForHCR(p.module, n[0].sym)
  let hcrCond = if forHcr: getTempName(p.module) else: nil
  var hcrGlobals: seq[tuple[loc: TLoc, tp: Rope]]
  # determine if the tuple is constructed at top-level scope or inside of a block (if/while/block)
  let isGlobalInBlock = forHcr and p.blocks.len > 2
  # do not close and reopen blocks if this is a 'global' but inside of a block (if/while/block)
  forHcr = forHcr and not isGlobalInBlock

  if forHcr:
    # check with the boolean if the initializing code for the tuple should be ran
    lineCg(p, cpsStmts, "if ($1)$n", [hcrCond])
    startBlock(p)

  genLineDir(p, n)
  initLocExpr(p, n[^1], tup)
  var t = tup.t.skipTypes(abstractInst)
  for i in 0..<n.len-2:
    let vn = n[i]
    let v = vn.sym
    if sfCompileTime in v.flags: continue
    var traverseProc: Rope
    if sfGlobal in v.flags:
      assignGlobalVar(p, vn, nil)
      genObjectInit(p, cpsInit, v.typ, v.loc, constructObj)
      traverseProc = getTraverseProc(p, v)
      if traverseProc != nil and not p.hcrOn:
        registerTraverseProc(p, v, traverseProc)
    else:
      assignLocalVar(p, vn)
      initLocalVar(p, v, immediateAsgn=isAssignedImmediately(p.config, n[^1]))
    initLoc(field, locExpr, vn, tup.storage)
    if t.kind == tyTuple:
      field.r = "$1.Field$2" % [rdLoc(tup), rope(i)]
    else:
      if t.n[i].kind != nkSym: internalError(p.config, n.info, "genVarTuple")
      field.r = "$1.$2" % [rdLoc(tup), mangleRecFieldName(p.module, t.n[i].sym)]
    putLocIntoDest(p, v.loc, field)
    if forHcr or isGlobalInBlock:
      hcrGlobals.add((loc: v.loc, tp: if traverseProc == nil: ~"NULL" else: traverseProc))

  if forHcr:
    # end the block where the tuple gets initialized
    endBlock(p)
  if forHcr or isGlobalInBlock:
    # insert the registration of the globals for the different parts of the tuple at the
    # start of the current scope (after they have been iterated) and init a boolean to
    # check if any of them is newly introduced and the initializing code has to be ran
    lineCg(p, cpsLocals, "NIM_BOOL $1 = NIM_FALSE;$n", [hcrCond])
    for curr in hcrGlobals:
      lineCg(p, cpsLocals, "$1 |= hcrRegisterGlobal($4, \"$2\", sizeof($3), $5, (void**)&$2);$N",
              [hcrCond, curr.loc.r, rdLoc(curr.loc), getModuleDllPath(p.module, n[0].sym), curr.tp])


proc loadInto(p: BProc, le, ri: PNode, a: var TLoc) {.inline.} =
  if ri.kind in nkCallKinds and (ri[0].kind != nkSym or
                                 ri[0].sym.magic == mNone):
    genAsgnCall(p, le, ri, a)
  else:
    # this is a hacky way to fix #1181 (tmissingderef)::
    #
    #  var arr1 = cast[ptr array[4, int8]](addr foo)[]
    #
    # However, fixing this properly really requires modelling 'array' as
    # a 'struct' in C to preserve dereferencing semantics completely. Not
    # worth the effort until version 1.0 is out.
    a.flags.incl(lfEnforceDeref)
    expr(p, ri, a)

proc assignLabel(b: var TBlock): Rope {.inline.} =
  b.label = "LA" & b.id.rope
  result = b.label

proc blockBody(b: var TBlock): Rope =
  result = b.sections[cpsLocals]
  if b.frameLen > 0:
    result.addf("FR_.len+=$1;$n", [b.frameLen.rope])
  result.add(b.sections[cpsInit])
  result.add(b.sections[cpsStmts])

proc endBlock(p: BProc, blockEnd: Rope) =
  let topBlock = p.blocks.len-1
  # the block is merged into the parent block
  p.blocks[topBlock-1].sections[cpsStmts].add(p.blocks[topBlock].blockBody)
  setLen(p.blocks, topBlock)
  # this is done after the block is popped so $n is
  # properly indented when pretty printing is enabled
  line(p, cpsStmts, blockEnd)

proc endBlock(p: BProc) =
  let topBlock = p.blocks.len - 1
  let frameLen = p.blocks[topBlock].frameLen
  var blockEnd: Rope
  if frameLen > 0:
    blockEnd.addf("FR_.len-=$1;$n", [frameLen.rope])
  if p.blocks[topBlock].label != nil:
    blockEnd.addf("} $1: ;$n", [p.blocks[topBlock].label])
  else:
    blockEnd.addf("}$n", [])
  endBlock(p, blockEnd)

proc genSimpleBlock(p: BProc, stmts: PNode) {.inline.} =
  startBlock(p)
  genStmts(p, stmts)
  endBlock(p)

proc exprBlock(p: BProc, n: PNode, d: var TLoc) =
  startBlock(p)
  expr(p, n, d)
  endBlock(p)

template preserveBreakIdx(body: untyped): untyped =
  var oldBreakIdx = p.breakIdx
  body
  p.breakIdx = oldBreakIdx

proc genState(p: BProc, n: PNode) =
  internalAssert p.config, n.len == 1
  let n0 = n[0]
  if n0.kind == nkIntLit:
    let idx = n[0].intVal
    linefmt(p, cpsStmts, "STATE$1: ;$n", [idx])
  elif n0.kind == nkStrLit:
    linefmt(p, cpsStmts, "$1: ;$n", [n0.strVal])

proc blockLeaveActions(p: BProc, howManyTrys, howManyExcepts: int) =
  # Called by return and break stmts.
  # Deals with issues faced when jumping out of try/except/finally stmts.

  var stack = newSeq[tuple[fin: PNode, inExcept: bool, label: Natural]](0)

  inc p.withinBlockLeaveActions
  for i in 1..howManyTrys:
    let tryStmt = p.nestedTryStmts.pop
    if p.config.exc == excSetjmp:
      # Pop safe points generated by try
      if not tryStmt.inExcept:
        linefmt(p, cpsStmts, "#popSafePoint();$n", [])

    # Pop this try-stmt of the list of nested trys
    # so we don't infinite recurse on it in the next step.
    stack.add(tryStmt)

    # Find finally-stmt for this try-stmt
    # and generate a copy of its sons
    var finallyStmt = tryStmt.fin
    if finallyStmt != nil:
      genStmts(p, finallyStmt[0])

  dec p.withinBlockLeaveActions

  # push old elements again:
  for i in countdown(howManyTrys-1, 0):
    p.nestedTryStmts.add(stack[i])

  # Pop exceptions that was handled by the
  # except-blocks we are in
  if noSafePoints notin p.flags:
    for i in countdown(howManyExcepts-1, 0):
      linefmt(p, cpsStmts, "#popCurrentException();$n", [])

proc genGotoState(p: BProc, n: PNode) =
  # we resist the temptation to translate it into duff's device as it later
  # will be translated into computed gotos anyway for GCC at least:
  # switch (x.state) {
  #   case 0: goto STATE0;
  # ...
  var a: TLoc
  initLocExpr(p, n[0], a)
  lineF(p, cpsStmts, "switch ($1) {$n", [rdLoc(a)])
  p.flags.incl beforeRetNeeded
  lineF(p, cpsStmts, "case -1:$n", [])
  blockLeaveActions(p,
    howManyTrys    = p.nestedTryStmts.len,
    howManyExcepts = p.inExceptBlockLen)
  lineF(p, cpsStmts, " goto BeforeRet_;$n", [])
  var statesCounter = lastOrd(p.config, n[0].typ)
  if n.len >= 2 and n[1].kind == nkIntLit:
    statesCounter = getInt(n[1])
  let prefix = if n.len == 3 and n[2].kind == nkStrLit: n[2].strVal.rope
               else: rope"STATE"
  for i in 0i64..toInt64(statesCounter):
    lineF(p, cpsStmts, "case $2: goto $1$2;$n", [prefix, rope(i)])
  lineF(p, cpsStmts, "}$n", [])

proc genBreakState(p: BProc, n: PNode, d: var TLoc) =
  var a: TLoc
  initLoc(d, locExpr, n, OnUnknown)

  if n[0].kind == nkClosure:
    initLocExpr(p, n[0][1], a)
    d.r = "(((NI*) $1)[1] < 0)" % [rdLoc(a)]
  else:
    initLocExpr(p, n[0], a)
    # the environment is guaranteed to contain the 'state' field at offset 1:
    d.r = "((((NI*) $1.ClE_0)[1]) < 0)" % [rdLoc(a)]

proc genGotoVar(p: BProc; value: PNode) =
  if value.kind notin {nkCharLit..nkUInt64Lit}:
    localError(p.config, value.info, "'goto' target must be a literal value")
  else:
    lineF(p, cpsStmts, "goto NIMSTATE_$#;$n", [value.intVal.rope])

proc genBracedInit(p: BProc, n: PNode; isConst: bool; optionalType: PType): Rope

proc potentialValueInit(p: BProc; v: PSym; value: PNode): Rope =
  if lfDynamicLib in v.loc.flags or sfThread in v.flags or p.hcrOn:
    result = nil
  elif sfGlobal in v.flags and value != nil and isDeepConstExpr(value, p.module.compileToCpp) and
      p.withinLoop == 0 and not containsGarbageCollectedRef(v.typ):
    #echo "New code produced for ", v.name.s, " ", p.config $ value.info
    result = genBracedInit(p, value, isConst = false, v.typ)
  else:
    result = nil

proc genSingleVar(p: BProc, v: PSym; vn, value: PNode) =
  if sfGoto in v.flags:
    # translate 'var state {.goto.} = X' into 'goto LX':
    genGotoVar(p, value)
    return
  var targetProc = p
  var traverseProc: Rope
  let valueAsRope = potentialValueInit(p, v, value)
  if sfGlobal in v.flags:
    if v.flags * {sfImportc, sfExportc} == {sfImportc} and
        value.kind == nkEmpty and
        v.loc.flags * {lfHeader, lfNoDecl} != {}:
      return
    if sfPure in v.flags:
      # v.owner.kind != skModule:
      targetProc = p.module.preInitProc
    assignGlobalVar(targetProc, vn, valueAsRope)
    # XXX: be careful here.
    # Global variables should not be zeromem-ed within loops
    # (see bug #20).
    # That's why we are doing the construction inside the preInitProc.
    # genObjectInit relies on the C runtime's guarantees that
    # global variables will be initialized to zero.
    if valueAsRope == nil:
      var loc = v.loc

      # When the native TLS is unavailable, a global thread-local variable needs
      # one more layer of indirection in order to access the TLS block.
      # Only do this for complex types that may need a call to `objectInit`
      if sfThread in v.flags and emulatedThreadVars(p.config) and
        isComplexValueType(v.typ):
        initLocExprSingleUse(p.module.preInitProc, vn, loc)
      genObjectInit(p.module.preInitProc, cpsInit, v.typ, loc, constructObj)
    # Alternative construction using default constructor (which may zeromem):
    # if sfImportc notin v.flags: constructLoc(p.module.preInitProc, v.loc)
    if sfExportc in v.flags and p.module.g.generatedHeader != nil:
      genVarPrototype(p.module.g.generatedHeader, vn)
    traverseProc = getTraverseProc(p, v)
    if traverseProc != nil and not p.hcrOn:
      registerTraverseProc(p, v, traverseProc)
  else:
    let imm = isAssignedImmediately(p.config, value)
    if imm and p.module.compileToCpp and p.splitDecls == 0 and
        not containsHiddenPointer(v.typ):
      # C++ really doesn't like things like 'Foo f; f = x' as that invokes a
      # parameterless constructor followed by an assignment operator. So we
      # generate better code here: 'Foo f = x;'
      genLineDir(p, vn)
      let decl = localVarDecl(p, vn)
      var tmp: TLoc
      if value.kind in nkCallKinds and value[0].kind == nkSym and
           sfConstructor in value[0].sym.flags:
        var params: Rope
        let typ = skipTypes(value[0].typ, abstractInst)
        assert(typ.kind == tyProc)
        for i in 1..<value.len:
          if params != nil: params.add(~", ")
          assert(typ.len == typ.n.len)
          params.add(genOtherArg(p, value, i, typ))
        if params == nil:
          lineF(p, cpsStmts, "$#;$n", [decl])
        else:
          lineF(p, cpsStmts, "$#($#);$n", [decl, params])
      else:
        initLocExprSingleUse(p, value, tmp)
        lineF(p, cpsStmts, "$# = $#;$n", [decl, tmp.rdLoc])
      return
    assignLocalVar(p, vn)
    initLocalVar(p, v, imm)

  if traverseProc == nil: traverseProc = ~"NULL"
  # If the var is in a block (control flow like if/while or a block) in global scope just
  # register the so called "global" so it can be used later on. There is no need to close
  # and reopen of if (nim_hcr_do_init_) blocks because we are in one already anyway.
  var forHcr = treatGlobalDifferentlyForHCR(p.module, v)
  if forHcr and targetProc.blocks.len > 3 and v.owner.kind == skModule:
    # put it in the locals section - mainly because of loops which
    # use the var in a call to resetLoc() in the statements section
    lineCg(targetProc, cpsLocals, "hcrRegisterGlobal($3, \"$1\", sizeof($2), $4, (void**)&$1);$n",
           [v.loc.r, rdLoc(v.loc), getModuleDllPath(p.module, v), traverseProc])
    # nothing special left to do later on - let's avoid closing and reopening blocks
    forHcr = false

  # we close and reopen the global if (nim_hcr_do_init_) blocks in the main Init function
  # for the module so we can have globals and top-level code be interleaved and still
  # be able to re-run it but without the top level code - just the init of globals
  if forHcr:
    lineCg(targetProc, cpsStmts, "if (hcrRegisterGlobal($3, \"$1\", sizeof($2), $4, (void**)&$1))$N",
           [v.loc.r, rdLoc(v.loc), getModuleDllPath(p.module, v), traverseProc])
    startBlock(targetProc)
  if value.kind != nkEmpty and valueAsRope == nil:
    genLineDir(targetProc, vn)
    loadInto(targetProc, vn, value, v.loc)
  if forHcr:
    endBlock(targetProc)

proc genSingleVar(p: BProc, a: PNode) =
  let v = a[0].sym
  if sfCompileTime in v.flags:
    # fix issue #12640
    # {.global, compileTime.} pragma in proc
    if sfGlobal in v.flags and p.prc != nil and p.prc.kind == skProc:
      discard
    else:
      return
  genSingleVar(p, v, a[0], a[2])

proc genClosureVar(p: BProc, a: PNode) =
  var immediateAsgn = a[2].kind != nkEmpty
  var v: TLoc
  initLocExpr(p, a[0], v)
  genLineDir(p, a)
  if immediateAsgn:
    loadInto(p, a[0], a[2], v)
  else:
    constructLoc(p, v)

proc genVarStmt(p: BProc, n: PNode) =
  for it in n.sons:
    if it.kind == nkCommentStmt: continue
    if it.kind == nkIdentDefs:
      # can be a lifted var nowadays ...
      if it[0].kind == nkSym:
        genSingleVar(p, it)
      else:
        genClosureVar(p, it)
    else:
      genVarTuple(p, it)

proc genIf(p: BProc, n: PNode, d: var TLoc) =
  #
  #  { if (!expr1) goto L1;
  #   thenPart }
  #  goto LEnd
  #  L1:
  #  { if (!expr2) goto L2;
  #   thenPart2 }
  #  goto LEnd
  #  L2:
  #  { elsePart }
  #  Lend:
  var
    a: TLoc
    lelse: TLabel
  if not isEmptyType(n.typ) and d.k == locNone:
    getTemp(p, n.typ, d)
  genLineDir(p, n)
  let lend = getLabel(p)
  for it in n.sons:
    # bug #4230: avoid false sharing between branches:
    if d.k == locTemp and isEmptyType(n.typ): d.k = locNone
    if it.len == 2:
      startBlock(p)
      initLocExprSingleUse(p, it[0], a)
      lelse = getLabel(p)
      inc(p.labels)
      lineF(p, cpsStmts, "if (!$1) goto $2;$n",
            [rdLoc(a), lelse])
      if p.module.compileToCpp:
        # avoid "jump to label crosses initialization" error:
        p.s(cpsStmts).add "{"
        expr(p, it[1], d)
        p.s(cpsStmts).add "}"
      else:
        expr(p, it[1], d)
      endBlock(p)
      if n.len > 1:
        lineF(p, cpsStmts, "goto $1;$n", [lend])
      fixLabel(p, lelse)
    elif it.len == 1:
      startBlock(p)
      expr(p, it[0], d)
      endBlock(p)
    else: internalError(p.config, n.info, "genIf()")
  if n.len > 1: fixLabel(p, lend)

proc genReturnStmt(p: BProc, t: PNode) =
  if nfPreventCg in t.flags: return
  p.flags.incl beforeRetNeeded
  genLineDir(p, t)
  if (t[0].kind != nkEmpty): genStmts(p, t[0])
  blockLeaveActions(p,
    howManyTrys    = p.nestedTryStmts.len,
    howManyExcepts = p.inExceptBlockLen)
  if (p.finallySafePoints.len > 0) and noSafePoints notin p.flags:
    # If we're in a finally block, and we came here by exception
    # consume it before we return.
    var safePoint = p.finallySafePoints[^1]
    linefmt(p, cpsStmts, "if ($1.status != 0) #popCurrentException();$n", [safePoint])
  lineF(p, cpsStmts, "goto BeforeRet_;$n", [])

proc genGotoForCase(p: BProc; caseStmt: PNode) =
  for i in 1..<caseStmt.len:
    startBlock(p)
    let it = caseStmt[i]
    for j in 0..<it.len-1:
      if it[j].kind == nkRange:
        localError(p.config, it.info, "range notation not available for computed goto")
        return
      let val = getOrdValue(it[j])
      lineF(p, cpsStmts, "NIMSTATE_$#:$n", [val.rope])
    genStmts(p, it.lastSon)
    endBlock(p)


iterator fieldValuePairs(n: PNode): tuple[memberSym, valueSym: PNode] =
  assert(n.kind in {nkLetSection, nkVarSection})
  for identDefs in n:
    if identDefs.kind == nkIdentDefs:
      let valueSym = identDefs[^1]
      for i in 0..<identDefs.len-2:
        let memberSym = identDefs[i]
        yield((memberSym: memberSym, valueSym: valueSym))

proc genComputedGoto(p: BProc; n: PNode) =
  # first pass: Generate array of computed labels:

  # flatten the loop body because otherwise let and var sections
  # wrapped inside stmt lists by inject destructors won't be recognised
  let n = n.flattenStmts()
  var casePos = -1
  var arraySize: int
  for i in 0..<n.len:
    let it = n[i]
    if it.kind == nkCaseStmt:
      if lastSon(it).kind != nkOfBranch:
        localError(p.config, it.info,
            "case statement must be exhaustive for computed goto"); return
      casePos = i
      if enumHasHoles(it[0].typ):
        localError(p.config, it.info,
            "case statement cannot work on enums with holes for computed goto"); return
      let aSize = lengthOrd(p.config, it[0].typ)
      if aSize > 10_000:
        localError(p.config, it.info,
            "case statement has too many cases for computed goto"); return
      arraySize = toInt(aSize)
      if firstOrd(p.config, it[0].typ) != 0:
        localError(p.config, it.info,
            "case statement has to start at 0 for computed goto"); return
  if casePos < 0:
    localError(p.config, n.info, "no case statement found for computed goto"); return
  var id = p.labels+1
  inc p.labels, arraySize+1
  let tmp = "TMP$1_" % [id.rope]
  var gotoArray = "static void* $#[$#] = {" % [tmp, arraySize.rope]
  for i in 1..arraySize-1:
    gotoArray.addf("&&TMP$#_, ", [rope(id+i)])
  gotoArray.addf("&&TMP$#_};$n", [rope(id+arraySize)])
  line(p, cpsLocals, gotoArray)

  for j in 0..<casePos:
    genStmts(p, n[j])

  let caseStmt = n[casePos]
  var a: TLoc
  initLocExpr(p, caseStmt[0], a)
  # first goto:
  lineF(p, cpsStmts, "goto *$#[$#];$n", [tmp, a.rdLoc])

  for i in 1..<caseStmt.len:
    startBlock(p)
    let it = caseStmt[i]
    for j in 0..<it.len-1:
      if it[j].kind == nkRange:
        localError(p.config, it.info, "range notation not available for computed goto")
        return

      let val = getOrdValue(it[j])
      lineF(p, cpsStmts, "TMP$#_:$n", [intLiteral(toInt64(val)+id+1)])

    genStmts(p, it.lastSon)

    for j in casePos+1..<n.len:
      genStmts(p, n[j])

    for j in 0..<casePos:
      # prevent new local declarations
      # compile declarations as assignments
      let it = n[j]
      if it.kind in {nkLetSection, nkVarSection}:
        let asgn = copyNode(it)
        asgn.transitionSonsKind(nkAsgn)
        asgn.sons.setLen 2
        for sym, value in it.fieldValuePairs:
          if value.kind != nkEmpty:
            asgn[0] = sym
            asgn[1] = value
            genStmts(p, asgn)
      else:
        genStmts(p, it)

    var a: TLoc
    initLocExpr(p, caseStmt[0], a)
    lineF(p, cpsStmts, "goto *$#[$#];$n", [tmp, a.rdLoc])
    endBlock(p)

  for j in casePos+1..<n.len:
    genStmts(p, n[j])


proc genWhileStmt(p: BProc, t: PNode) =
  # we don't generate labels here as for example GCC would produce
  # significantly worse code
  var
    a: TLoc
  assert(t.len == 2)
  inc(p.withinLoop)
  genLineDir(p, t)

  preserveBreakIdx:
    var loopBody = t[1]
    if loopBody.stmtsContainPragma(wComputedGoto) and
       hasComputedGoto in CC[p.config.cCompiler].props:
         # for closure support weird loop bodies are generated:
      if loopBody.len == 2 and loopBody[0].kind == nkEmpty:
        loopBody = loopBody[1]
      genComputedGoto(p, loopBody)
    else:
      p.breakIdx = startBlock(p, "while (1) {$n")
      p.blocks[p.breakIdx].isLoop = true
      initLocExpr(p, t[0], a)
      if (t[0].kind != nkIntLit) or (t[0].intVal == 0):
        let label = assignLabel(p.blocks[p.breakIdx])
        lineF(p, cpsStmts, "if (!$1) goto $2;$n", [rdLoc(a), label])
      genStmts(p, loopBody)

      if optProfiler in p.options:
        # invoke at loop body exit:
        linefmt(p, cpsStmts, "#nimProfile();$n", [])
      endBlock(p)

  dec(p.withinLoop)

proc genBlock(p: BProc, n: PNode, d: var TLoc) =
  if not isEmptyType(n.typ):
    # bug #4505: allocate the temp in the outer scope
    # so that it can escape the generated {}:
    if d.k == locNone:
      getTemp(p, n.typ, d)
    d.flags.incl(lfEnforceDeref)
  preserveBreakIdx:
    p.breakIdx = startBlock(p)
    if n[0].kind != nkEmpty:
      # named block?
      assert(n[0].kind == nkSym)
      var sym = n[0].sym
      sym.loc.k = locOther
      sym.position = p.breakIdx+1
    expr(p, n[1], d)
    endBlock(p)

proc genParForStmt(p: BProc, t: PNode) =
  assert(t.len == 3)
  inc(p.withinLoop)
  genLineDir(p, t)

  preserveBreakIdx:
    let forLoopVar = t[0].sym
    var rangeA, rangeB: TLoc
    assignLocalVar(p, t[0])
    #initLoc(forLoopVar.loc, locLocalVar, forLoopVar.typ, onStack)
    #discard mangleName(forLoopVar)
    let call = t[1]
    assert(call.len in {4, 5})
    initLocExpr(p, call[1], rangeA)
    initLocExpr(p, call[2], rangeB)

    # $n at the beginning because of #9710
    if call.len == 4: # procName(a, b, annotation)
      if call[0].sym.name.s == "||":  # `||`(a, b, annotation)
        lineF(p, cpsStmts, "$n#pragma omp $4$n" &
                            "for ($1 = $2; $1 <= $3; ++$1)",
                            [forLoopVar.loc.rdLoc,
                            rangeA.rdLoc, rangeB.rdLoc,
                            call[3].getStr.rope])
      else:
        lineF(p, cpsStmts, "$n#pragma $4$n" &
                    "for ($1 = $2; $1 <= $3; ++$1)",
                    [forLoopVar.loc.rdLoc,
                    rangeA.rdLoc, rangeB.rdLoc,
                    call[3].getStr.rope])
    else: # `||`(a, b, step, annotation)
      var step: TLoc
      initLocExpr(p, call[3], step)
      lineF(p, cpsStmts, "$n#pragma omp $5$n" &
                    "for ($1 = $2; $1 <= $3; $1 += $4)",
                    [forLoopVar.loc.rdLoc,
                    rangeA.rdLoc, rangeB.rdLoc, step.rdLoc,
                    call[4].getStr.rope])

    p.breakIdx = startBlock(p)
    p.blocks[p.breakIdx].isLoop = true
    genStmts(p, t[2])
    endBlock(p)

  dec(p.withinLoop)

proc genBreakStmt(p: BProc, t: PNode) =
  var idx = p.breakIdx
  if t[0].kind != nkEmpty:
    # named break?
    assert(t[0].kind == nkSym)
    var sym = t[0].sym
    doAssert(sym.loc.k == locOther)
    idx = sym.position-1
  else:
    # an unnamed 'break' can only break a loop after 'transf' pass:
    while idx >= 0 and not p.blocks[idx].isLoop: dec idx
    if idx < 0 or not p.blocks[idx].isLoop:
      internalError(p.config, t.info, "no loop to break")
  let label = assignLabel(p.blocks[idx])
  blockLeaveActions(p,
    p.nestedTryStmts.len - p.blocks[idx].nestedTryStmts,
    p.inExceptBlockLen - p.blocks[idx].nestedExceptStmts)
  genLineDir(p, t)
  lineF(p, cpsStmts, "goto $1;$n", [label])

proc raiseExit(p: BProc) =
  assert p.config.exc == excGoto
  if nimErrorFlagDisabled notin p.flags:
    p.flags.incl nimErrorFlagAccessed
    if p.nestedTryStmts.len == 0:
      p.flags.incl beforeRetNeeded
      # easy case, simply goto 'ret':
      lineCg(p, cpsStmts, "if (NIM_UNLIKELY(*nimErr_)) goto BeforeRet_;$n", [])
    else:
      lineCg(p, cpsStmts, "if (NIM_UNLIKELY(*nimErr_)) goto LA$1_;$n",
        [p.nestedTryStmts[^1].label])

proc finallyActions(p: BProc) =
  if p.config.exc != excGoto and p.nestedTryStmts.len > 0 and p.nestedTryStmts[^1].inExcept:
    # if the current try stmt have a finally block,
    # we must execute it before reraising
    let finallyBlock = p.nestedTryStmts[^1].fin
    if finallyBlock != nil:
      genSimpleBlock(p, finallyBlock[0])

proc raiseInstr(p: BProc): Rope =
  if p.config.exc == excGoto:
    let L = p.nestedTryStmts.len
    if L == 0:
      p.flags.incl beforeRetNeeded
      # easy case, simply goto 'ret':
      result = ropecg(p.module, "goto BeforeRet_;$n", [])
    else:
      # raise inside an 'except' must go to the finally block,
      # raise outside an 'except' block must go to the 'except' list.
      result = ropecg(p.module, "goto LA$1_;$n",
        [p.nestedTryStmts[L-1].label])
      # + ord(p.nestedTryStmts[L-1].inExcept)])
  else:
    result = nil

proc genRaiseStmt(p: BProc, t: PNode) =
  if t[0].kind != nkEmpty:
    var a: TLoc
    initLocExprSingleUse(p, t[0], a)
    finallyActions(p)
    var e = rdLoc(a)
    discard getTypeDesc(p.module, t[0].typ)
    var typ = skipTypes(t[0].typ, abstractPtrs)
    # XXX For reasons that currently escape me, this is only required by the new
    # C++ based exception handling:
    if p.config.exc == excCpp:
      blockLeaveActions(p, howManyTrys = 0, howManyExcepts = p.inExceptBlockLen)
    genLineDir(p, t)
    if isImportedException(typ, p.config):
      lineF(p, cpsStmts, "throw $1;$n", [e])
    else:
      lineCg(p, cpsStmts, "#raiseExceptionEx((#Exception*)$1, $2, $3, $4, $5);$n",
          [e, makeCString(typ.sym.name.s),
          makeCString(if p.prc != nil: p.prc.name.s else: p.module.module.name.s),
          quotedFilename(p.config, t.info), toLinenumber(t.info)])
      if optOwnedRefs in p.config.globalOptions:
        lineCg(p, cpsStmts, "$1 = NIM_NIL;$n", [e])
  else:
    finallyActions(p)
    genLineDir(p, t)
    # reraise the last exception:
    if p.config.exc == excCpp:
      line(p, cpsStmts, ~"throw;$n")
    else:
      linefmt(p, cpsStmts, "#reraiseException();$n", [])
  let gotoInstr = raiseInstr(p)
  if gotoInstr != nil:
    line(p, cpsStmts, gotoInstr)

template genCaseGenericBranch(p: BProc, b: PNode, e: TLoc,
                          rangeFormat, eqFormat: FormatStr, labl: TLabel) =
  var x, y: TLoc
  for i in 0..<b.len - 1:
    if b[i].kind == nkRange:
      initLocExpr(p, b[i][0], x)
      initLocExpr(p, b[i][1], y)
      lineCg(p, cpsStmts, rangeFormat,
           [rdCharLoc(e), rdCharLoc(x), rdCharLoc(y), labl])
    else:
      initLocExpr(p, b[i], x)
      lineCg(p, cpsStmts, eqFormat, [rdCharLoc(e), rdCharLoc(x), labl])

proc genCaseSecondPass(p: BProc, t: PNode, d: var TLoc,
                       labId, until: int): TLabel =
  var lend = getLabel(p)
  for i in 1..until:
    # bug #4230: avoid false sharing between branches:
    if d.k == locTemp and isEmptyType(t.typ): d.k = locNone
    lineF(p, cpsStmts, "LA$1_: ;$n", [rope(labId + i)])
    if t[i].kind == nkOfBranch:
      exprBlock(p, t[i][^1], d)
      lineF(p, cpsStmts, "goto $1;$n", [lend])
    else:
      exprBlock(p, t[i][0], d)
  result = lend

template genIfForCaseUntil(p: BProc, t: PNode, d: var TLoc,
                       rangeFormat, eqFormat: FormatStr,
                       until: int, a: TLoc): TLabel =
  # generate a C-if statement for a Nim case statement
  var res: TLabel
  var labId = p.labels
  for i in 1..until:
    inc(p.labels)
    if t[i].kind == nkOfBranch: # else statement
      genCaseGenericBranch(p, t[i], a, rangeFormat, eqFormat,
                           "LA" & rope(p.labels) & "_")
    else:
      lineF(p, cpsStmts, "goto LA$1_;$n", [rope(p.labels)])
  if until < t.len-1:
    inc(p.labels)
    var gotoTarget = p.labels
    lineF(p, cpsStmts, "goto LA$1_;$n", [rope(gotoTarget)])
    res = genCaseSecondPass(p, t, d, labId, until)
    lineF(p, cpsStmts, "LA$1_: ;$n", [rope(gotoTarget)])
  else:
    res = genCaseSecondPass(p, t, d, labId, until)
  res

template genCaseGeneric(p: BProc, t: PNode, d: var TLoc,
                    rangeFormat, eqFormat: FormatStr) =
  var a: TLoc
  initLocExpr(p, t[0], a)
  var lend = genIfForCaseUntil(p, t, d, rangeFormat, eqFormat, t.len-1, a)
  fixLabel(p, lend)

proc genCaseStringBranch(p: BProc, b: PNode, e: TLoc, labl: TLabel,
                         branches: var openArray[Rope]) =
  var x: TLoc
  for i in 0..<b.len - 1:
    assert(b[i].kind != nkRange)
    initLocExpr(p, b[i], x)
    assert(b[i].kind in {nkStrLit..nkTripleStrLit})
    var j = int(hashString(p.config, b[i].strVal) and high(branches))
    appcg(p.module, branches[j], "if (#eqStrings($1, $2)) goto $3;$n",
         [rdLoc(e), rdLoc(x), labl])

proc genStringCase(p: BProc, t: PNode, d: var TLoc) =
  # count how many constant strings there are in the case:
  var strings = 0
  for i in 1..<t.len:
    if t[i].kind == nkOfBranch: inc(strings, t[i].len - 1)
  if strings > stringCaseThreshold:
    var bitMask = math.nextPowerOfTwo(strings) - 1
    var branches: seq[Rope]
    newSeq(branches, bitMask + 1)
    var a: TLoc
    initLocExpr(p, t[0], a) # fist pass: generate ifs+goto:
    var labId = p.labels
    for i in 1..<t.len:
      inc(p.labels)
      if t[i].kind == nkOfBranch:
        genCaseStringBranch(p, t[i], a, "LA" & rope(p.labels) & "_",
                            branches)
      else:
        # else statement: nothing to do yet
        # but we reserved a label, which we use later
        discard
    linefmt(p, cpsStmts, "switch (#hashString($1) & $2) {$n",
            [rdLoc(a), bitMask])
    for j in 0..high(branches):
      if branches[j] != nil:
        lineF(p, cpsStmts, "case $1: $n$2break;$n",
             [intLiteral(j), branches[j]])
    lineF(p, cpsStmts, "}$n", []) # else statement:
    if t[^1].kind != nkOfBranch:
      lineF(p, cpsStmts, "goto LA$1_;$n", [rope(p.labels)])
    # third pass: generate statements
    var lend = genCaseSecondPass(p, t, d, labId, t.len-1)
    fixLabel(p, lend)
  else:
    genCaseGeneric(p, t, d, "", "if (#eqStrings($1, $2)) goto $3;$n")

proc branchHasTooBigRange(b: PNode): bool =
  for it in b:
    # last son is block
    if (it.kind == nkRange) and
        it[1].intVal - it[0].intVal > RangeExpandLimit:
      return true

proc ifSwitchSplitPoint(p: BProc, n: PNode): int =
  for i in 1..<n.len:
    var branch = n[i]
    var stmtBlock = lastSon(branch)
    if stmtBlock.stmtsContainPragma(wLinearScanEnd):
      result = i
    elif hasSwitchRange notin CC[p.config.cCompiler].props:
      if branch.kind == nkOfBranch and branchHasTooBigRange(branch):
        result = i

proc genCaseRange(p: BProc, branch: PNode) =
  for j in 0..<branch.len-1:
    if branch[j].kind == nkRange:
      if hasSwitchRange in CC[p.config.cCompiler].props:
        lineF(p, cpsStmts, "case $1 ... $2:$n", [
            genLiteral(p, branch[j][0]),
            genLiteral(p, branch[j][1])])
      else:
        var v = copyNode(branch[j][0])
        while v.intVal <= branch[j][1].intVal:
          lineF(p, cpsStmts, "case $1:$n", [genLiteral(p, v)])
          inc(v.intVal)
    else:
      lineF(p, cpsStmts, "case $1:$n", [genLiteral(p, branch[j])])

proc genOrdinalCase(p: BProc, n: PNode, d: var TLoc) =
  # analyse 'case' statement:
  var splitPoint = ifSwitchSplitPoint(p, n)

  # generate if part (might be empty):
  var a: TLoc
  initLocExpr(p, n[0], a)
  var lend = if splitPoint > 0: genIfForCaseUntil(p, n, d,
                    rangeFormat = "if ($1 >= $2 && $1 <= $3) goto $4;$n",
                    eqFormat = "if ($1 == $2) goto $3;$n",
                    splitPoint, a) else: nil

  # generate switch part (might be empty):
  if splitPoint+1 < n.len:
    lineF(p, cpsStmts, "switch ($1) {$n", [rdCharLoc(a)])
    var hasDefault = false
    for i in splitPoint+1..<n.len:
      # bug #4230: avoid false sharing between branches:
      if d.k == locTemp and isEmptyType(n.typ): d.k = locNone
      var branch = n[i]
      if branch.kind == nkOfBranch:
        genCaseRange(p, branch)
      else:
        # else part of case statement:
        lineF(p, cpsStmts, "default:$n", [])
        hasDefault = true
      exprBlock(p, branch.lastSon, d)
      lineF(p, cpsStmts, "break;$n", [])
    if (hasAssume in CC[p.config.cCompiler].props) and not hasDefault:
      lineF(p, cpsStmts, "default: __assume(0);$n", [])
    lineF(p, cpsStmts, "}$n", [])
  if lend != nil: fixLabel(p, lend)

proc genCase(p: BProc, t: PNode, d: var TLoc) =
  genLineDir(p, t)
  if not isEmptyType(t.typ) and d.k == locNone:
    getTemp(p, t.typ, d)
  case skipTypes(t[0].typ, abstractVarRange).kind
  of tyString:
    genStringCase(p, t, d)
  of tyFloat..tyFloat128:
    genCaseGeneric(p, t, d, "if ($1 >= $2 && $1 <= $3) goto $4;$n",
                            "if ($1 == $2) goto $3;$n")
  else:
    if t[0].kind == nkSym and sfGoto in t[0].sym.flags:
      genGotoForCase(p, t)
    else:
      genOrdinalCase(p, t, d)

proc genRestoreFrameAfterException(p: BProc) =
  if optStackTrace in p.module.config.options:
    if hasCurFramePointer notin p.flags:
      p.flags.incl hasCurFramePointer
      p.procSec(cpsLocals).add(ropecg(p.module, "\tTFrame* _nimCurFrame;$n", []))
      p.procSec(cpsInit).add(ropecg(p.module, "\t_nimCurFrame = #getFrame();$n", []))
    linefmt(p, cpsStmts, "#setFrame(_nimCurFrame);$n", [])

proc genTryCpp(p: BProc, t: PNode, d: var TLoc) =
  #[ code to generate:

    std::exception_ptr error = nullptr;
    try {
      body;
    } catch (Exception e) {
      error = std::current_exception();
      if (ofExpr(e, TypeHere)) {

        error = nullptr; // handled
      } else if (...) {

      } else {
        throw;
      }
    } catch(...) {
      // C++ exception occured, not under Nim's control.
    }
    {
      /* finally: */
      printf('fin!\n');
      if (error) std::rethrow_exception(error); // re-raise the exception
    }
  ]#
  p.module.includeHeader("<exception>")

  if not isEmptyType(t.typ) and d.k == locNone:
    getTemp(p, t.typ, d)
  genLineDir(p, t)

  inc(p.labels, 2)
  let etmp = p.labels

  p.procSec(cpsInit).add(ropecg(p.module, "\tstd::exception_ptr T$1_ = nullptr;", [etmp]))

  let fin = if t[^1].kind == nkFinally: t[^1] else: nil
  p.nestedTryStmts.add((fin, false, 0.Natural))

  if t.kind == nkHiddenTryStmt:
    lineCg(p, cpsStmts, "try {$n", [])
    expr(p, t[0], d)
    lineCg(p, cpsStmts, "}$n", [])
  else:
    startBlock(p, "try {$n")
    expr(p, t[0], d)
    endBlock(p)

  # First pass: handle Nim based exceptions:
  lineCg(p, cpsStmts, "catch (#Exception* T$1_) {$n", [etmp+1])
  genRestoreFrameAfterException(p)
  # an unhandled exception happened!
  lineCg(p, cpsStmts, "T$1_ = std::current_exception();$n", [etmp])
  p.nestedTryStmts[^1].inExcept = true
  var hasImportedCppExceptions = false
  var i = 1
  var hasIf = false
  var hasElse = false
  while (i < t.len) and (t[i].kind == nkExceptBranch):
    # bug #4230: avoid false sharing between branches:
    if d.k == locTemp and isEmptyType(t.typ): d.k = locNone
    if t[i].len == 1:
      hasImportedCppExceptions = true
      # general except section:
      hasElse = true
      if hasIf: lineF(p, cpsStmts, "else ", [])
      startBlock(p)
      # we handled the error:
      linefmt(p, cpsStmts, "T$1_ = nullptr;$n", [etmp])
      expr(p, t[i][0], d)
      linefmt(p, cpsStmts, "#popCurrentException();$n", [])
      endBlock(p)
    else:
      var orExpr = Rope(nil)
      var exvar = PNode(nil)
      for j in 0..<t[i].len - 1:
        var typeNode = t[i][j]
        if t[i][j].isInfixAs():
          typeNode = t[i][j][1]
          exvar = t[i][j][2] # ex1 in `except ExceptType as ex1:`
        assert(typeNode.kind == nkType)
        if isImportedException(typeNode.typ, p.config):
          hasImportedCppExceptions = true
        else:
          if orExpr != nil: orExpr.add("||")
          let checkFor = if optTinyRtti in p.config.globalOptions:
            genTypeInfo2Name(p.module, typeNode.typ)
          else:
            genTypeInfoV1(p.module, typeNode.typ, typeNode.info)
          let memberName = if p.module.compileToCpp: "m_type" else: "Sup.m_type"
          appcg(p.module, orExpr, "#isObj(#nimBorrowCurrentException()->$1, $2)", [memberName, checkFor])

      if orExpr != nil:
        if hasIf:
          startBlock(p, "else if ($1) {$n", [orExpr])
        else:
          startBlock(p, "if ($1) {$n", [orExpr])
          hasIf = true
        if exvar != nil:
          fillLoc(exvar.sym.loc, locTemp, exvar, mangleLocalName(p, exvar.sym), OnStack)
          linefmt(p, cpsStmts, "$1 $2 = T$3_;$n", [getTypeDesc(p.module, exvar.sym.typ),
            rdLoc(exvar.sym.loc), rope(etmp+1)])
        # we handled the error:
        linefmt(p, cpsStmts, "T$1_ = nullptr;$n", [etmp])
        expr(p, t[i][^1], d)
        linefmt(p, cpsStmts, "#popCurrentException();$n", [])
        endBlock(p)
    inc(i)
  if hasIf and not hasElse:
    linefmt(p, cpsStmts, "else throw;$n", [etmp])
  linefmt(p, cpsStmts, "}$n", [])

  # Second pass: handle C++ based exceptions:
  template genExceptBranchBody(body: PNode) {.dirty.} =
    genRestoreFrameAfterException(p)
    #linefmt(p, cpsStmts, "T$1_ = std::current_exception();$n", [etmp])
    expr(p, body, d)

  var catchAllPresent = false
  incl p.flags, noSafePoints # mark as not needing 'popCurrentException'
  if hasImportedCppExceptions:
    for i in 1..<t.len:
      if t[i].kind != nkExceptBranch: break

      # bug #4230: avoid false sharing between branches:
      if d.k == locTemp and isEmptyType(t.typ): d.k = locNone

      if t[i].len == 1:
        # general except section:
        startBlock(p, "catch (...) {", [])
        genExceptBranchBody(t[i][0])
        endBlock(p)
        catchAllPresent = true
      else:
        for j in 0..<t[i].len-1:
          var typeNode = t[i][j]
          if t[i][j].isInfixAs():
            typeNode = t[i][j][1]
            if isImportedException(typeNode.typ, p.config):
              let exvar = t[i][j][2] # ex1 in `except ExceptType as ex1:`
              fillLoc(exvar.sym.loc, locTemp, exvar, mangleLocalName(p, exvar.sym), OnStack)
              startBlock(p, "catch ($1& $2) {$n", getTypeDesc(p.module, typeNode.typ), rdLoc(exvar.sym.loc))
              genExceptBranchBody(t[i][^1])  # exception handler body will duplicated for every type
              endBlock(p)
          elif isImportedException(typeNode.typ, p.config):
            startBlock(p, "catch ($1&) {$n", getTypeDesc(p.module, t[i][j].typ))
            genExceptBranchBody(t[i][^1])  # exception handler body will duplicated for every type
            endBlock(p)

  excl p.flags, noSafePoints
  discard pop(p.nestedTryStmts)
  # general finally block:
  if t.len > 0 and t[^1].kind == nkFinally:
    if not catchAllPresent:
      startBlock(p, "catch (...) {", [])
      genRestoreFrameAfterException(p)
      linefmt(p, cpsStmts, "T$1_ = std::current_exception();$n", [etmp])
      endBlock(p)

    startBlock(p)
    genStmts(p, t[^1][0])
    linefmt(p, cpsStmts, "if (T$1_) std::rethrow_exception(T$1_);$n", [etmp])
    endBlock(p)

proc genTryCppOld(p: BProc, t: PNode, d: var TLoc) =
  # There are two versions we generate, depending on whether we
  # catch C++ exceptions, imported via .importcpp or not. The
  # code can be easier if there are no imported C++ exceptions
  # to deal with.

  # code to generate:
  #
  #   try
  #   {
  #      myDiv(4, 9);
  #   } catch (NimExceptionType1&) {
  #      body
  #   } catch (NimExceptionType2&) {
  #      finallyPart()
  #      raise;
  #   }
  #   catch(...) {
  #     general_handler_body
  #   }
  #   finallyPart();

  template genExceptBranchBody(body: PNode) {.dirty.} =
    genRestoreFrameAfterException(p)
    expr(p, body, d)

  if not isEmptyType(t.typ) and d.k == locNone:
    getTemp(p, t.typ, d)
  genLineDir(p, t)
  discard cgsym(p.module, "popCurrentExceptionEx")
  let fin = if t[^1].kind == nkFinally: t[^1] else: nil
  p.nestedTryStmts.add((fin, false, 0.Natural))
  startBlock(p, "try {$n")
  expr(p, t[0], d)
  endBlock(p)

  var catchAllPresent = false

  p.nestedTryStmts[^1].inExcept = true
  for i in 1..<t.len:
    if t[i].kind != nkExceptBranch: break

    # bug #4230: avoid false sharing between branches:
    if d.k == locTemp and isEmptyType(t.typ): d.k = locNone

    if t[i].len == 1:
      # general except section:
      catchAllPresent = true
      startBlock(p, "catch (...) {$n")
      genExceptBranchBody(t[i][0])
      endBlock(p)
    else:
      for j in 0..<t[i].len-1:
        if t[i][j].isInfixAs():
          let exvar = t[i][j][2] # ex1 in `except ExceptType as ex1:`
          fillLoc(exvar.sym.loc, locTemp, exvar, mangleLocalName(p, exvar.sym), OnUnknown)
          startBlock(p, "catch ($1& $2) {$n", getTypeDesc(p.module, t[i][j][1].typ), rdLoc(exvar.sym.loc))
        else:
          startBlock(p, "catch ($1&) {$n", getTypeDesc(p.module, t[i][j].typ))
        genExceptBranchBody(t[i][^1])  # exception handler body will duplicated for every type
        endBlock(p)

  discard pop(p.nestedTryStmts)

  if t[^1].kind == nkFinally:
    # c++ does not have finally, therefore code needs to be generated twice
    if not catchAllPresent:
      # finally requires catch all presence
      startBlock(p, "catch (...) {$n")
      genStmts(p, t[^1][0])
      line(p, cpsStmts, ~"throw;$n")
      endBlock(p)

    genSimpleBlock(p, t[^1][0])

proc bodyCanRaise(p: BProc; n: PNode): bool =
  case n.kind
  of nkCallKinds:
    result = canRaiseDisp(p, n[0])
    if not result:
      # also check the arguments:
      for i in 1 ..< n.len:
        if bodyCanRaise(p, n[i]): return true
  of nkRaiseStmt:
    result = true
  of nkTypeSection, nkProcDef, nkConverterDef, nkMethodDef, nkIteratorDef,
      nkMacroDef, nkTemplateDef, nkLambda, nkDo, nkFuncDef:
    result = false
  else:
    for i in 0 ..< safeLen(n):
      if bodyCanRaise(p, n[i]): return true
    result = false

proc genTryGoto(p: BProc; t: PNode; d: var TLoc) =
  let fin = if t[^1].kind == nkFinally: t[^1] else: nil
  inc p.labels
  let lab = p.labels
  let hasExcept = t[1].kind == nkExceptBranch
  if hasExcept: inc p.withinTryWithExcept
  p.nestedTryStmts.add((fin, false, Natural lab))

  p.flags.incl nimErrorFlagAccessed

  if not isEmptyType(t.typ) and d.k == locNone:
    getTemp(p, t.typ, d)

  expr(p, t[0], d)

  if 1 < t.len and t[1].kind == nkExceptBranch:
    startBlock(p, "if (NIM_UNLIKELY(*nimErr_)) {$n")
  else:
    startBlock(p)
  linefmt(p, cpsStmts, "LA$1_:;$n", [lab])

  p.nestedTryStmts[^1].inExcept = true
  var i = 1
  while (i < t.len) and (t[i].kind == nkExceptBranch):

    inc p.labels
    let nextExcept = p.labels
    p.nestedTryStmts[^1].label = nextExcept

    # bug #4230: avoid false sharing between branches:
    if d.k == locTemp and isEmptyType(t.typ): d.k = locNone
    if t[i].len == 1:
      # general except section:
      if i > 1: lineF(p, cpsStmts, "else", [])
      startBlock(p)
      # we handled the exception, remember this:
      linefmt(p, cpsStmts, "*nimErr_ = NIM_FALSE;$n", [])
      expr(p, t[i][0], d)
    else:
      var orExpr: Rope = nil
      for j in 0..<t[i].len - 1:
        assert(t[i][j].kind == nkType)
        if orExpr != nil: orExpr.add("||")
        let checkFor = if optTinyRtti in p.config.globalOptions:
          genTypeInfo2Name(p.module, t[i][j].typ)
        else:
          genTypeInfoV1(p.module, t[i][j].typ, t[i][j].info)
        let memberName = if p.module.compileToCpp: "m_type" else: "Sup.m_type"
        appcg(p.module, orExpr, "#isObj(#nimBorrowCurrentException()->$1, $2)", [memberName, checkFor])

      if i > 1: line(p, cpsStmts, "else ")
      startBlock(p, "if ($1) {$n", [orExpr])
      # we handled the exception, remember this:
      linefmt(p, cpsStmts, "*nimErr_ = NIM_FALSE;$n", [])
      expr(p, t[i][^1], d)

    linefmt(p, cpsStmts, "#popCurrentException();$n", [])
    linefmt(p, cpsStmts, "LA$1_:;$n", [nextExcept])
    endBlock(p)

    inc(i)
  discard pop(p.nestedTryStmts)
  endBlock(p)

  if i < t.len and t[i].kind == nkFinally:
    startBlock(p)
    if not bodyCanRaise(p, t[i][0]):
      # this is an important optimization; most destroy blocks are detected not to raise an
      # exception and so we help the C optimizer by not mutating nimErr_ pointlessly:
      genStmts(p, t[i][0])
    else:
      # pretend we did handle the error for the safe execution of the 'finally' section:
      p.procSec(cpsLocals).add(ropecg(p.module, "NIM_BOOL oldNimErrFin$1_;$n", [lab]))
      linefmt(p, cpsStmts, "oldNimErrFin$1_ = *nimErr_; *nimErr_ = NIM_FALSE;$n", [lab])
      genStmts(p, t[i][0])
      # this is correct for all these cases:
      # 1. finally is run during ordinary control flow
      # 2. finally is run after 'except' block handling: these however set the
      #    error back to nil.
      # 3. finally is run for exception handling code without any 'except'
      #    handler present or only handlers that did not match.
      linefmt(p, cpsStmts, "*nimErr_ = oldNimErrFin$1_;$n", [lab])
    endBlock(p)
  raiseExit(p)
  if hasExcept: inc p.withinTryWithExcept

proc genTrySetjmp(p: BProc, t: PNode, d: var TLoc) =
  # code to generate:
  #
  # XXX: There should be a standard dispatch algorithm
  # that's used both here and with multi-methods
  #
  #  TSafePoint sp;
  #  pushSafePoint(&sp);
  #  sp.status = setjmp(sp.context);
  #  if (sp.status == 0) {
  #    myDiv(4, 9);
  #    popSafePoint();
  #  } else {
  #    popSafePoint();
  #    /* except DivisionByZero: */
  #    if (sp.status == DivisionByZero) {
  #      printf('Division by Zero\n');
  #      clearException();
  #    } else {
  #      clearException();
  #    }
  #  }
  #  {
  #    /* finally: */
  #    printf('fin!\n');
  #  }
  #  if (exception not cleared)
  #    propagateCurrentException();
  #
  if not isEmptyType(t.typ) and d.k == locNone:
    getTemp(p, t.typ, d)
  let quirkyExceptions = p.config.exc == excQuirky or
      (t.kind == nkHiddenTryStmt and sfSystemModule in p.module.module.flags)
  if not quirkyExceptions:
    p.module.includeHeader("<setjmp.h>")
  else:
    p.flags.incl noSafePoints
  genLineDir(p, t)
  discard cgsym(p.module, "Exception")
  var safePoint: Rope
  if not quirkyExceptions:
    safePoint = getTempName(p.module)
    linefmt(p, cpsLocals, "#TSafePoint $1;$n", [safePoint])
    linefmt(p, cpsStmts, "#pushSafePoint(&$1);$n", [safePoint])
    if isDefined(p.config, "nimStdSetjmp"):
      linefmt(p, cpsStmts, "$1.status = setjmp($1.context);$n", [safePoint])
    elif isDefined(p.config, "nimSigSetjmp"):
      linefmt(p, cpsStmts, "$1.status = sigsetjmp($1.context, 0);$n", [safePoint])
    elif isDefined(p.config, "nimRawSetjmp"):
      linefmt(p, cpsStmts, "$1.status = _setjmp($1.context);$n", [safePoint])
    else:
      linefmt(p, cpsStmts, "$1.status = setjmp($1.context);$n", [safePoint])
    lineCg(p, cpsStmts, "if ($1.status == 0) {$n", [safePoint])
  let fin = if t[^1].kind == nkFinally: t[^1] else: nil
  p.nestedTryStmts.add((fin, quirkyExceptions, 0.Natural))
  expr(p, t[0], d)
  if not quirkyExceptions:
    linefmt(p, cpsStmts, "#popSafePoint();$n", [])
    lineCg(p, cpsStmts, "}$n", [])
    startBlock(p, "else {$n")
    linefmt(p, cpsStmts, "#popSafePoint();$n", [])
    genRestoreFrameAfterException(p)
  elif 1 < t.len and t[1].kind == nkExceptBranch:
    startBlock(p, "if (#nimBorrowCurrentException()) {$n")
  else:
    startBlock(p)
  p.nestedTryStmts[^1].inExcept = true
  var i = 1
  while (i < t.len) and (t[i].kind == nkExceptBranch):
    # bug #4230: avoid false sharing between branches:
    if d.k == locTemp and isEmptyType(t.typ): d.k = locNone
    if t[i].len == 1:
      # general except section:
      if i > 1: lineF(p, cpsStmts, "else", [])
      startBlock(p)
      if not quirkyExceptions:
        linefmt(p, cpsStmts, "$1.status = 0;$n", [safePoint])
      expr(p, t[i][0], d)
      linefmt(p, cpsStmts, "#popCurrentException();$n", [])
      endBlock(p)
    else:
      var orExpr: Rope = nil
      for j in 0..<t[i].len - 1:
        assert(t[i][j].kind == nkType)
        if orExpr != nil: orExpr.add("||")
        let checkFor = if optTinyRtti in p.config.globalOptions:
          genTypeInfo2Name(p.module, t[i][j].typ)
        else:
          genTypeInfoV1(p.module, t[i][j].typ, t[i][j].info)
        let memberName = if p.module.compileToCpp: "m_type" else: "Sup.m_type"
        appcg(p.module, orExpr, "#isObj(#nimBorrowCurrentException()->$1, $2)", [memberName, checkFor])

      if i > 1: line(p, cpsStmts, "else ")
      startBlock(p, "if ($1) {$n", [orExpr])
      if not quirkyExceptions:
        linefmt(p, cpsStmts, "$1.status = 0;$n", [safePoint])
      expr(p, t[i][^1], d)
      linefmt(p, cpsStmts, "#popCurrentException();$n", [])
      endBlock(p)
    inc(i)
  discard pop(p.nestedTryStmts)
  endBlock(p) # end of else block
  if i < t.len and t[i].kind == nkFinally:
    p.finallySafePoints.add(safePoint)
    startBlock(p)
    genStmts(p, t[i][0])
    # pretend we handled the exception in a 'finally' so that we don't
    # re-raise the unhandled one but instead keep the old one (it was
    # not popped either):
    if not quirkyExceptions and getCompilerProc(p.module.g.graph, "nimLeaveFinally") != nil:
      linefmt(p, cpsStmts, "if ($1.status != 0) #nimLeaveFinally();$n", [safePoint])
    endBlock(p)
    discard pop(p.finallySafePoints)
  if not quirkyExceptions:
    linefmt(p, cpsStmts, "if ($1.status != 0) #reraiseException();$n", [safePoint])

proc genAsmOrEmitStmt(p: BProc, t: PNode, isAsmStmt=false): Rope =
  var res = ""
  for it in t.sons:
    case it.kind
    of nkStrLit..nkTripleStrLit:
      res.add(it.strVal)
    of nkSym:
      var sym = it.sym
      if sym.kind in {skProc, skFunc, skIterator, skMethod}:
        var a: TLoc
        initLocExpr(p, it, a)
        res.add($rdLoc(a))
      elif sym.kind == skType:
        res.add($getTypeDesc(p.module, sym.typ))
      else:
        discard getTypeDesc(p.module, skipTypes(sym.typ, abstractPtrs))
        var r = sym.loc.r
        if r == nil:
          # if no name has already been given,
          # it doesn't matter much:
          r = mangleName(p.module, sym)
          sym.loc.r = r       # but be consequent!
        res.add($r)
    of nkTypeOfExpr:
      res.add($getTypeDesc(p.module, it.typ))
    else:
      discard getTypeDesc(p.module, skipTypes(it.typ, abstractPtrs))
      var a: TLoc
      initLocExpr(p, it, a)
      res.add($a.rdLoc)

  if isAsmStmt and hasGnuAsm in CC[p.config.cCompiler].props:
    for x in splitLines(res):
      var j = 0
      while j < x.len and x[j] in {' ', '\t'}: inc(j)
      if j < x.len:
        if x[j] in {'"', ':'}:
          # don't modify the line if already in quotes or
          # some clobber register list:
          result.add(x); result.add("\L")
        else:
          # ignore empty lines
          result.add("\"")
          result.add(x.replace("\"", "\\\""))
          result.add("\\n\"\n")
  else:
    res.add("\L")
    result = res.rope

proc genAsmStmt(p: BProc, t: PNode) =
  assert(t.kind == nkAsmStmt)
  genLineDir(p, t)
  var s = genAsmOrEmitStmt(p, t, isAsmStmt=true)
  # see bug #2362, "top level asm statements" seem to be a mis-feature
  # but even if we don't do this, the example in #2362 cannot possibly
  # work:
  if p.prc == nil:
    # top level asm statement?
    p.module.s[cfsProcHeaders].add runtimeFormat(CC[p.config.cCompiler].asmStmtFrmt, [s])
  else:
    p.s(cpsStmts).add indentLine(p, runtimeFormat(CC[p.config.cCompiler].asmStmtFrmt, [s]))

proc determineSection(n: PNode): TCFileSection =
  result = cfsProcHeaders
  if n.len >= 1 and n[0].kind in {nkStrLit..nkTripleStrLit}:
    let sec = n[0].strVal
    if sec.startsWith("/*TYPESECTION*/"): result = cfsTypes
    elif sec.startsWith("/*VARSECTION*/"): result = cfsVars
    elif sec.startsWith("/*INCLUDESECTION*/"): result = cfsHeaders

proc genEmit(p: BProc, t: PNode) =
  var s = genAsmOrEmitStmt(p, t[1])
  if p.prc == nil:
    # top level emit pragma?
    let section = determineSection(t[1])
    genCLineDir(p.module.s[section], t.info, p.config)
    p.module.s[section].add(s)
  else:
    genLineDir(p, t)
    line(p, cpsStmts, s)

proc genPragma(p: BProc, n: PNode) =
  for it in n.sons:
    case whichPragma(it)
    of wEmit: genEmit(p, it)
    of wInjectStmt:
      var p = newProc(nil, p.module)
      p.options.excl {optLineTrace, optStackTrace}
      genStmts(p, it[1])
      p.module.injectStmt = p.s(cpsStmts)
    else: discard


proc genDiscriminantCheck(p: BProc, a, tmp: TLoc, objtype: PType,
                          field: PSym) =
  var t = skipTypes(objtype, abstractVar)
  assert t.kind == tyObject
  discard genTypeInfoV1(p.module, t, a.lode.info)
  if not containsOrIncl(p.module.declaredThings, field.id):
    appcg(p.module, cfsVars, "extern $1",
          [discriminatorTableDecl(p.module, t, field)])
  lineCg(p, cpsStmts,
        "#FieldDiscriminantCheck((NI)(NU)($1), (NI)(NU)($2), $3, $4);$n",
        [rdLoc(a), rdLoc(tmp), discriminatorTableName(p.module, t, field),
         intLiteral(toInt64(lengthOrd(p.config, field.typ))+1)])

when false:
  proc genCaseObjDiscMapping(p: BProc, e: PNode, t: PType, field: PSym; d: var TLoc) =
    const ObjDiscMappingProcSlot = -5
    var theProc: PSym = nil
    for idx, p in items(t.methods):
      if idx == ObjDiscMappingProcSlot:
        theProc = p
        break
    if theProc == nil:
      theProc = genCaseObjDiscMapping(t, field, e.info, p.module.g.graph, p.module.idgen)
      t.methods.add((ObjDiscMappingProcSlot, theProc))
    var call = newNodeIT(nkCall, e.info, getSysType(p.module.g.graph, e.info, tyUInt8))
    call.add newSymNode(theProc)
    call.add e
    expr(p, call, d)

proc asgnFieldDiscriminant(p: BProc, e: PNode) =
  var a, tmp: TLoc
  var dotExpr = e[0]
  if dotExpr.kind == nkCheckedFieldExpr: dotExpr = dotExpr[0]
  initLocExpr(p, e[0], a)
  getTemp(p, a.t, tmp)
  expr(p, e[1], tmp)
  if optTinyRtti notin p.config.globalOptions:
    let field = dotExpr[1].sym
    genDiscriminantCheck(p, a, tmp, dotExpr[0].typ, field)
    message(p.config, e.info, warnCaseTransition)
  genAssignment(p, a, tmp, {})

proc genAsgn(p: BProc, e: PNode, fastAsgn: bool) =
  if e[0].kind == nkSym and sfGoto in e[0].sym.flags:
    genLineDir(p, e)
    genGotoVar(p, e[1])
  elif optFieldCheck in p.options and isDiscriminantField(e[0]):
    genLineDir(p, e)
    asgnFieldDiscriminant(p, e)
  else:
    let le = e[0]
    let ri = e[1]
    var a: TLoc
    discard getTypeDesc(p.module, le.typ.skipTypes(skipPtrs), skVar)
    initLoc(a, locNone, le, OnUnknown)
    a.flags.incl(lfEnforceDeref)
    a.flags.incl(lfPrepareForMutation)
    expr(p, le, a)
    a.flags.excl(lfPrepareForMutation)
    if fastAsgn: incl(a.flags, lfNoDeepCopy)
    assert(a.t != nil)
    genLineDir(p, ri)
    loadInto(p, le, ri, a)

proc genStmts(p: BProc, t: PNode) =
  var a: TLoc

  let isPush = p.config.hasHint(hintExtendedContext)
  if isPush: pushInfoContext(p.config, t.info)
  expr(p, t, a)
  if isPush: popInfoContext(p.config)
  internalAssert p.config, a.k in {locNone, locTemp, locLocalVar, locExpr}