path: root/compiler/cgen.nim

#
#
#           The Nimrod Compiler
#        (c) Copyright 2014 Andreas Rumpf
#
#    See the file "copying.txt", included in this
#    distribution, for details about the copyright.
#

## This module implements the C code generator.

import 
  ast, astalgo, strutils, hashes, trees, platform, magicsys, extccomp,
  options, intsets,
  nversion, nimsets, msgs, crc, bitsets, idents, lists, types, ccgutils, os,
  times, ropes, math, passes, rodread, wordrecg, treetab, cgmeth,
  rodutils, renderer, idgen, cgendata, ccgmerge, semfold, aliases, lowerings

when options.hasTinyCBackend:
  import tccgen

# implementation

var
  generatedHeader: BModule

proc ropeff(cformat, llvmformat: string, args: varargs[PRope]): PRope = 
  if gCmd == cmdCompileToLLVM: result = ropef(llvmformat, args)
  else: result = ropef(cformat, args)
  
proc appff(dest: var PRope, cformat, llvmformat: string, 
           args: varargs[PRope]) = 
  if gCmd == cmdCompileToLLVM: appf(dest, llvmformat, args)
  else: appf(dest, cformat, args)
  
proc addForwardedProc(m: BModule, prc: PSym) = 
  m.forwardedProcs.add(prc)
  inc(gForwardedProcsCounter)

proc getCgenModule(s: PSym): BModule =
  result = if s.position >= 0 and s.position < gModules.len: gModules[s.position]
           else: nil

proc findPendingModule(m: BModule, s: PSym): BModule = 
  var ms = getModule(s)
  result = gModules[ms.position]

proc emitLazily(s: PSym): bool {.inline.} =
  result = optDeadCodeElim in gGlobalOptions or
           sfDeadCodeElim in getModule(s).flags

proc initLoc(result: var TLoc, k: TLocKind, typ: PType, s: TStorageLoc) = 
  result.k = k
  result.s = s
  result.t = getUniqueType(typ)
  result.r = nil
  result.a = - 1
  result.flags = {}

proc fillLoc(a: var TLoc, k: TLocKind, typ: PType, r: PRope, s: TStorageLoc) = 
  # fills the loc if it is not already initialized
  if a.k == locNone: 
    a.k = k
    a.t = getUniqueType(typ)
    a.a = - 1
    a.s = s
    if a.r == nil: a.r = r
  
proc isSimpleConst(typ: PType): bool =
  let t = skipTypes(typ, abstractVar)
  result = t.kind notin
      {tyTuple, tyObject, tyArray, tyArrayConstr, tySet, tySequence} and not
      (t.kind == tyProc and t.callConv == ccClosure)

proc useStringh(m: BModule) =
  if not m.includesStringh:
    m.includesStringh = true
    discard lists.includeStr(m.headerFiles, "<string.h>")

proc useHeader(m: BModule, sym: PSym) = 
  if lfHeader in sym.loc.flags: 
    assert(sym.annex != nil)
    discard lists.includeStr(m.headerFiles, getStr(sym.annex.path))

proc cgsym(m: BModule, name: string): PRope

proc ropecg(m: BModule, frmt: TFormatStr, args: varargs[PRope]): PRope = 
  var i = 0
  var length = len(frmt)
  result = nil
  var num = 0
  while i < length: 
    if frmt[i] == '$': 
      inc(i)                  # skip '$'
      case frmt[i]
      of '$': 
        app(result, "$")
        inc(i)
      of '#': 
        inc(i)
        app(result, args[num])
        inc(num)
      of '0'..'9': 
        var j = 0
        while true: 
          j = (j * 10) + ord(frmt[i]) - ord('0')
          inc(i)
          if i >= length or not (frmt[i] in {'0'..'9'}): break 
        num = j
        if j > high(args) + 1: 
          internalError("ropes: invalid format string $" & $j)
        app(result, args[j-1])
      of 'n':
        if optLineDir notin gOptions: app(result, rnl)
        inc(i)
      of 'N': 
        app(result, rnl)
        inc(i)
      else: internalError("ropes: invalid format string $" & frmt[i])
    elif frmt[i] == '#' and frmt[i+1] in IdentStartChars:
      inc(i)
      var j = i
      while frmt[j] in IdentChars: inc(j)
      var ident = substr(frmt, i, j-1)
      i = j
      app(result, cgsym(m, ident))
    elif frmt[i] == '#' and frmt[i+1] == '$':
      inc(i, 2)
      var j = 0
      while frmt[i] in Digits: 
        j = (j * 10) + ord(frmt[i]) - ord('0')
        inc(i)
      app(result, cgsym(m, args[j-1].ropeToStr))
    var start = i
    while i < length: 
      if frmt[i] != '$' and frmt[i] != '#': inc(i)
      else: break 
    if i - 1 >= start: 
      app(result, substr(frmt, start, i - 1))

const compileTimeRopeFmt = not defined(booting)

when compileTimeRopeFmt:
  import macros

  type TFmtFragmentKind = enum
    ffSym,
    ffLit,
    ffParam

  type TFragment = object
    case kind: TFmtFragmentKind
    of ffSym, ffLit:
      value: string
    of ffParam:
      intValue: int

  iterator fmtStringFragments(s: string): tuple[kind: TFmtFragmentKind,
                                                value: string,
                                                intValue: int] =
    # This is a bit less featured version of the ropecg's algorithm
    # (be careful when replacing ropecg calls)
    var
      i = 0
      length = s.len

    while i < length:
      var start = i
      case s[i]
      of '$':
        let n = s[i+1]
        case n
        of '$':
          inc i, 2
        of '0'..'9':
          # XXX: use the new case object construction syntax when it's ready
          yield (kind: ffParam, value: "", intValue: n.ord - ord('1'))
          inc i, 2
          start = i
        else:
          inc i
      of '#':
        inc i
        var j = i
        while s[i] in IdentChars: inc i
        yield (kind: ffSym, value: substr(s, j, i-1), intValue: 0)
        start = i
      else: nil

      while i < length:
        if s[i] != '$' and s[i] != '#': inc i
        else: break

      if i - 1 >= start:
        yield (kind: ffLit, value: substr(s, start, i-1), intValue: 0)

  macro rfmt(m: BModule, fmt: static[string], args: varargs[PRope]): expr =
    ## Experimental optimized rope-formatting operator
    ## The run-time code it produces will be very fast, but will it speed up
    ## the compilation of nimrod itself or will the macro execution time
    ## offset the gains?
    result = newCall(bindSym"ropeConcat")
    for frag in fmtStringFragments(fmt.strVal):
      case frag.kind
      of ffSym:
        result.add(newCall(bindSym"cgsym", m, newStrLitNode(frag.value)))
      of ffLit:
        result.add(newCall(bindSym"~", newStrLitNode(frag.value)))
      of ffParam:
        result.add(args[frag.intValue])
else:
  template rfmt(m: BModule, fmt: string, args: varargs[PRope]): expr =
    ropecg(m, fmt, args)

proc appcg(m: BModule, c: var PRope, frmt: TFormatStr, 
           args: varargs[PRope]) = 
  app(c, ropecg(m, frmt, args))

proc appcg(m: BModule, s: TCFileSection, frmt: TFormatStr, 
           args: varargs[PRope]) = 
  app(m.s[s], ropecg(m, frmt, args))

proc appcg(p: BProc, s: TCProcSection, frmt: TFormatStr, 
           args: varargs[PRope]) = 
  app(p.s(s), ropecg(p.module, frmt, args))

var indent = "\t".toRope
proc indentLine(p: BProc, r: PRope): PRope =
  result = r
  for i in countup(0, p.blocks.len-1): prepend(result, indent)
  
proc line(p: BProc, s: TCProcSection, r: PRope) =
  app(p.s(s), indentLine(p, r))

proc line(p: BProc, s: TCProcSection, r: string) =
  app(p.s(s), indentLine(p, r.toRope))

proc lineF(p: BProc, s: TCProcSection, frmt: TFormatStr,
              args: varargs[PRope]) =
  app(p.s(s), indentLine(p, ropef(frmt, args)))

proc lineCg(p: BProc, s: TCProcSection, frmt: TFormatStr,
               args: varargs[PRope]) =
  app(p.s(s), indentLine(p, ropecg(p.module, frmt, args)))

when compileTimeRopeFmt:
  template linefmt(p: BProc, s: TCProcSection, frmt: TFormatStr,
                   args: varargs[PRope]) =
    line(p, s, rfmt(p.module, frmt, args))
else:
  proc linefmt(p: BProc, s: TCProcSection, frmt: TFormatStr,
               args: varargs[PRope]) =
    app(p.s(s), indentLine(p, ropecg(p.module, frmt, args)))

proc appLineCg(p: BProc, r: var PRope, frmt: TFormatStr,
               args: varargs[PRope]) =
  app(r, indentLine(p, ropecg(p.module, frmt, args)))

proc lineFF(p: BProc, s: TCProcSection, cformat, llvmformat: string,
               args: varargs[PRope]) =
  if gCmd == cmdCompileToLLVM: lineF(p, s, llvmformat, args)
  else: lineF(p, s, cformat, args)

proc safeLineNm(info: TLineInfo): int =
  result = toLinenumber(info)
  if result < 0: result = 0 # negative numbers are not allowed in #line

proc genCLineDir(r: var PRope, filename: string, line: int) =
  assert line >= 0
  if optLineDir in gOptions:
    appff(r, "$N#line $2 $1$N", "; line $2 \"$1\"$n",
          [toRope(makeSingleLineCString(filename)), toRope(line)])

proc genCLineDir(r: var PRope, info: TLineInfo) = 
  genCLineDir(r, info.toFullPath, info.safeLineNm)

proc genLineDir(p: BProc, t: PNode) =
  var line = t.info.safeLineNm
  if optEmbedOrigSrc in gGlobalOptions:
    app(p.s(cpsStmts), con(~"//", t.info.sourceLine, rnl))
  genCLineDir(p.s(cpsStmts), t.info.toFullPath, line)
  if ({optStackTrace, optEndb} * p.options == {optStackTrace, optEndb}) and
      (p.prc == nil or sfPure notin p.prc.flags):
    linefmt(p, cpsStmts, "#endb($1, $2);$n",
            line.toRope, makeCString(toFilename(t.info)))
  elif ({optLineTrace, optStackTrace} * p.options ==
      {optLineTrace, optStackTrace}) and
      (p.prc == nil or sfPure notin p.prc.flags):
    linefmt(p, cpsStmts, "nimln($1, $2);$n",
            line.toRope, t.info.quotedFilename)

proc postStmtActions(p: BProc) {.inline.} =
  app(p.s(cpsStmts), p.module.injectStmt)

proc accessThreadLocalVar(p: BProc, s: PSym)
proc emulatedThreadVars(): bool {.inline.}

include "ccgtypes.nim"

# ------------------------------ Manager of temporaries ------------------

proc rdLoc(a: TLoc): PRope =
  # 'read' location (deref if indirect)
  result = a.r
  if lfIndirect in a.flags: result = ropef("(*$1)", [result])

proc addrLoc(a: TLoc): PRope =
  result = a.r
  if lfIndirect notin a.flags and mapType(a.t) != ctArray:
    result = con("&", result)

proc rdCharLoc(a: TLoc): PRope =
  # read a location that may need a char-cast:
  result = rdLoc(a)
  if skipTypes(a.t, abstractRange).kind == tyChar:
    result = ropef("((NU8)($1))", [result])

proc genObjectInit(p: BProc, section: TCProcSection, t: PType, a: TLoc,
                   takeAddr: bool) =
  case analyseObjectWithTypeField(t)
  of frNone:
    discard
  of frHeader:
    var r = rdLoc(a)
    if not takeAddr: r = ropef("(*$1)", [r])
    var s = skipTypes(t, abstractInst)
    if gCmd != cmdCompileToCpp:
      while (s.kind == tyObject) and (s.sons[0] != nil):
        app(r, ".Sup")
        s = skipTypes(s.sons[0], abstractInst)
    linefmt(p, section, "$1.m_type = $2;$n", r, genTypeInfo(p.module, t))
  of frEmbedded:
    # worst case for performance:
    var r = if takeAddr: addrLoc(a) else: rdLoc(a)
    linefmt(p, section, "#objectInit($1, $2);$n", r, genTypeInfo(p.module, t))

type
  TAssignmentFlag = enum
    needToCopy, needForSubtypeCheck, afDestIsNil, afDestIsNotNil, afSrcIsNil,
    afSrcIsNotNil, needToKeepAlive
  TAssignmentFlags = set[TAssignmentFlag]

proc genRefAssign(p: BProc, dest, src: TLoc, flags: TAssignmentFlags)

proc isComplexValueType(t: PType): bool {.inline.} =
  result = t.kind in {tyArray, tyArrayConstr, tySet, tyTuple, tyObject} or
    (t.kind == tyProc and t.callConv == ccClosure)

proc resetLoc(p: BProc, loc: var TLoc) =
  let containsGcRef = containsGarbageCollectedRef(loc.t)
  if not isComplexValueType(skipTypes(loc.t, abstractVarRange)):
    if containsGcRef:
      var nilLoc: TLoc
      initLoc(nilLoc, locTemp, loc.t, OnStack)
      nilLoc.r = toRope("NIM_NIL")
      genRefAssign(p, loc, nilLoc, {afSrcIsNil})
    else:
      linefmt(p, cpsStmts, "$1 = 0;$n", rdLoc(loc))
  else:
    if optNilCheck in p.options:
      linefmt(p, cpsStmts, "#chckNil((void*)$1);$n", addrLoc(loc))
    if loc.s != OnStack:
      linefmt(p, cpsStmts, "#genericReset((void*)$1, $2);$n",
              addrLoc(loc), genTypeInfo(p.module, loc.t))
      # XXX: generated reset procs should not touch the m_type
      # field, so disabling this should be safe:
      genObjectInit(p, cpsStmts, loc.t, loc, true)
    else:
      useStringh(p.module)
      linefmt(p, cpsStmts, "memset((void*)$1, 0, sizeof($2));$n",
              addrLoc(loc), rdLoc(loc))
      # XXX: We can be extra clever here and call memset only 
      # on the bytes following the m_type field?
      genObjectInit(p, cpsStmts, loc.t, loc, true)

proc constructLoc(p: BProc, loc: TLoc, isTemp = false) =
  if not isComplexValueType(skipTypes(loc.t, abstractRange)):
    linefmt(p, cpsStmts, "$1 = 0;$n", rdLoc(loc))
  else:
    if not isTemp or containsGarbageCollectedRef(loc.t):
      # don't use memset for temporary values for performance if we can
      # avoid it:
      useStringh(p.module)
      linefmt(p, cpsStmts, "memset((void*)$1, 0, sizeof($2));$n",
              addrLoc(loc), rdLoc(loc))
    genObjectInit(p, cpsStmts, loc.t, loc, true)

proc initLocalVar(p: BProc, v: PSym, immediateAsgn: bool) =
  if sfNoInit notin v.flags:
    # we know it is a local variable and thus on the stack!
    # If ``not immediateAsgn`` it is not initialized in a binding like
    # ``var v = X`` and thus we need to init it. 
    # If ``v`` contains a GC-ref we may pass it to ``unsureAsgnRef`` somehow
    # which requires initialization. However this can really only happen if
    # ``var v = X()`` gets transformed into ``X(&v)``. 
    # Nowadays the logic in ccgcalls deals with this case however.
    if not immediateAsgn:
      constructLoc(p, v.loc)

proc getTemp(p: BProc, t: PType, result: var TLoc) = 
  inc(p.labels)
  if gCmd == cmdCompileToLLVM: 
    result.r = con("%LOC", toRope(p.labels))
  else: 
    result.r = con("LOC", toRope(p.labels))
    linefmt(p, cpsLocals, "$1 $2;$n", getTypeDesc(p.module, t), result.r)
  result.k = locTemp
  result.a = - 1
  result.t = getUniqueType(t)
  result.s = OnStack
  result.flags = {}
  constructLoc(p, result, isTemp=true)

proc keepAlive(p: BProc, toKeepAlive: TLoc) =
  when false:
    # deactivated because of the huge slowdown this causes; GC will take care
    # of interior pointers instead
    if optRefcGC notin gGlobalOptions: return
    var result: TLoc
    var fid = toRope(p.gcFrameId)
    result.r = con("GCFRAME.F", fid)
    appf(p.gcFrameType, "  $1 F$2;$n",
        [getTypeDesc(p.module, toKeepAlive.t), fid])
    inc(p.gcFrameId)
    result.k = locTemp
    result.a = -1
    result.t = toKeepAlive.t
    result.s = OnStack
    result.flags = {}

    if not isComplexValueType(skipTypes(toKeepAlive.t, abstractVarRange)):
      linefmt(p, cpsStmts, "$1 = $2;$n", rdLoc(result), rdLoc(toKeepAlive))
    else:
      useStringh(p.module)
      linefmt(p, cpsStmts,
           "memcpy((void*)$1, (NIM_CONST void*)$2, sizeof($3));$n",
           addrLoc(result), addrLoc(toKeepAlive), rdLoc(result))

proc initGCFrame(p: BProc): PRope =
  if p.gcFrameId > 0: result = ropef("struct {$1} GCFRAME;$n", p.gcFrameType)

proc deinitGCFrame(p: BProc): PRope =
  if p.gcFrameId > 0:
    result = ropecg(p.module,
                    "if (((NU)&GCFRAME) < 4096) #nimGCFrame(&GCFRAME);$n")

proc cstringLit(p: BProc, r: var PRope, s: string): PRope = 
  if gCmd == cmdCompileToLLVM: 
    inc(p.module.labels)
    inc(p.labels)
    result = ropef("%LOC$1", [toRope(p.labels)])
    appf(p.module.s[cfsData], "@C$1 = private constant [$2 x i8] $3$n", 
         [toRope(p.module.labels), toRope(len(s)), makeLLVMString(s)])
    appf(r, "$1 = getelementptr [$2 x i8]* @C$3, %NI 0, %NI 0$n", 
         [result, toRope(len(s)), toRope(p.module.labels)])
  else: 
    result = makeCString(s)
  
proc cstringLit(m: BModule, r: var PRope, s: string): PRope = 
  if gCmd == cmdCompileToLLVM: 
    inc(m.labels, 2)
    result = ropef("%MOC$1", [toRope(m.labels - 1)])
    appf(m.s[cfsData], "@MOC$1 = private constant [$2 x i8] $3$n", 
         [toRope(m.labels), toRope(len(s)), makeLLVMString(s)])
    appf(r, "$1 = getelementptr [$2 x i8]* @MOC$3, %NI 0, %NI 0$n", 
         [result, toRope(len(s)), toRope(m.labels)])
  else: 
    result = makeCString(s)
  
proc allocParam(p: BProc, s: PSym) = 
  assert(s.kind == skParam)
  if lfParamCopy notin s.loc.flags: 
    inc(p.labels)
    var tmp = con("%LOC", toRope(p.labels))
    incl(s.loc.flags, lfParamCopy)
    incl(s.loc.flags, lfIndirect)
    lineF(p, cpsInit, "$1 = alloca $3$n" & "store $3 $2, $3* $1$n",
         [tmp, s.loc.r, getTypeDesc(p.module, s.loc.t)])
    s.loc.r = tmp

proc localDebugInfo(p: BProc, s: PSym) = 
  if {optStackTrace, optEndb} * p.options != {optStackTrace, optEndb}: return 
  # XXX work around a bug: No type information for open arrays possible:
  if skipTypes(s.typ, abstractVar).kind in {tyOpenArray, tyVarargs}: return
  var a = con("&", s.loc.r)
  if s.kind == skParam and ccgIntroducedPtr(s): a = s.loc.r
  lineF(p, cpsInit,
       "F.s[$1].address = (void*)$3; F.s[$1].typ = $4; F.s[$1].name = $2;$n",
       [p.maxFrameLen.toRope, makeCString(normalize(s.name.s)), a,
        genTypeInfo(p.module, s.loc.t)])
  inc(p.maxFrameLen)
  inc p.blocks[p.blocks.len-1].frameLen

proc assignLocalVar(p: BProc, s: PSym) = 
  #assert(s.loc.k == locNone) // not yet assigned
  # this need not be fullfilled for inline procs; they are regenerated
  # for each module that uses them!
  if s.loc.k == locNone: 
    fillLoc(s.loc, locLocalVar, s.typ, mangleName(s), OnStack)
    if s.kind == skLet: incl(s.loc.flags, lfNoDeepCopy)
  var decl = getTypeDesc(p.module, s.loc.t)
  if s.constraint.isNil:
    if sfRegister in s.flags: app(decl, " register")
    #elif skipTypes(s.typ, abstractInst).kind in GcTypeKinds:
    #  app(decl, " GC_GUARD")
    if sfVolatile in s.flags or p.nestedTryStmts.len > 0: 
      app(decl, " volatile")
    appf(decl, " $1;$n", [s.loc.r])
  else:
    decl = ropef(s.cgDeclFrmt & ";$n", decl, s.loc.r)
  line(p, cpsLocals, decl)
  localDebugInfo(p, s)

include ccgthreadvars

proc varInDynamicLib(m: BModule, sym: PSym)
proc mangleDynLibProc(sym: PSym): PRope

proc assignGlobalVar(p: BProc, s: PSym) = 
  if s.loc.k == locNone: 
    fillLoc(s.loc, locGlobalVar, s.typ, mangleName(s), OnHeap)
  
  if lfDynamicLib in s.loc.flags:
    var q = findPendingModule(p.module, s)
    if q != nil and not containsOrIncl(q.declaredThings, s.id): 
      varInDynamicLib(q, s)
    else:
      s.loc.r = mangleDynLibProc(s)
    return
  useHeader(p.module, s)
  if lfNoDecl in s.loc.flags: return
  if sfThread in s.flags: 
    declareThreadVar(p.module, s, sfImportc in s.flags)
  else: 
    var decl: PRope = nil
    var td = getTypeDesc(p.module, s.loc.t)
    if s.constraint.isNil:
      if sfImportc in s.flags: app(decl, "extern ")
      app(decl, td)
      if sfRegister in s.flags: app(decl, " register")
      if sfVolatile in s.flags: app(decl, " volatile")
      appf(decl, " $1;$n", [s.loc.r])
    else:
      decl = ropef(s.cgDeclFrmt & ";$n", td, s.loc.r)
    app(p.module.s[cfsVars], decl)
  if p.withinLoop > 0:
    # fixes tests/run/tzeroarray:
    resetLoc(p, s.loc)
  if p.module.module.options * {optStackTrace, optEndb} ==
                               {optStackTrace, optEndb}: 
    appcg(p.module, p.module.s[cfsDebugInit], 
          "#dbgRegisterGlobal($1, &$2, $3);$n", 
         [cstringLit(p, p.module.s[cfsDebugInit], 
          normalize(s.owner.name.s & '.' & s.name.s)), 
          s.loc.r, genTypeInfo(p.module, s.typ)])
  
proc assignParam(p: BProc, s: PSym) = 
  assert(s.loc.r != nil)
  if sfAddrTaken in s.flags and gCmd == cmdCompileToLLVM: allocParam(p, s)
  localDebugInfo(p, s)

proc fillProcLoc(sym: PSym) = 
  if sym.loc.k == locNone: 
    fillLoc(sym.loc, locProc, sym.typ, mangleName(sym), OnStack)
  
proc getLabel(p: BProc): TLabel = 
  inc(p.labels)
  result = con("LA", toRope(p.labels))

proc fixLabel(p: BProc, labl: TLabel) = 
  lineF(p, cpsStmts, "$1: ;$n", [labl])

proc genVarPrototype(m: BModule, sym: PSym)
proc requestConstImpl(p: BProc, sym: PSym)
proc genProc(m: BModule, prc: PSym)
proc genStmts(p: BProc, t: PNode)
proc expr(p: BProc, n: PNode, d: var TLoc)
proc genProcPrototype(m: BModule, sym: PSym)
proc putLocIntoDest(p: BProc, d: var TLoc, s: TLoc)
proc genAssignment(p: BProc, dest, src: TLoc, flags: TAssignmentFlags)
proc intLiteral(i: BiggestInt): PRope
proc genLiteral(p: BProc, n: PNode): PRope

proc initLocExpr(p: BProc, e: PNode, result: var TLoc) =
  initLoc(result, locNone, e.typ, OnUnknown)
  expr(p, e, result)

proc lenField: PRope {.inline.} =
  result = toRope(if gCmd != cmdCompileToCpp: "Sup.len" else: "len")

include ccgcalls, "ccgstmts.nim", "ccgexprs.nim"

# ----------------------------- dynamic library handling -----------------
# We don't finalize dynamic libs as this does the OS for us.

proc isGetProcAddr(lib: PLib): bool =
  let n = lib.path
  result = n.kind in nkCallKinds and n.typ != nil and 
    n.typ.kind in {tyPointer, tyProc}

proc loadDynamicLib(m: BModule, lib: PLib) = 
  assert(lib != nil)
  if not lib.generated: 
    lib.generated = true
    var tmp = getGlobalTempName()
    assert(lib.name == nil)
    lib.name = tmp # BUGFIX: cgsym has awful side-effects
    appf(m.s[cfsVars], "static void* $1;$n", [tmp])
    if lib.path.kind in {nkStrLit..nkTripleStrLit}:
      var s: TStringSeq = @[]
      libCandidates(lib.path.strVal, s)
      if gVerbosity >= 2:
        msgWriteln("Dependency: " & lib.path.strVal)
      var loadlib: PRope = nil
      for i in countup(0, high(s)): 
        inc(m.labels)
        if i > 0: app(loadlib, "||")
        appcg(m, loadlib, "($1 = #nimLoadLibrary((#NimStringDesc*) &$2))$n", 
              [tmp, getStrLit(m, s[i])])
      appcg(m, m.s[cfsDynLibInit], 
            "if (!($1)) #nimLoadLibraryError((#NimStringDesc*) &$2);$n", 
            [loadlib, getStrLit(m, lib.path.strVal)]) 
    else:
      var p = newProc(nil, m)
      p.options = p.options - {optStackTrace, optEndb}
      var dest: TLoc
      initLocExpr(p, lib.path, dest)
      app(m.s[cfsVars], p.s(cpsLocals))
      app(m.s[cfsDynLibInit], p.s(cpsInit))
      app(m.s[cfsDynLibInit], p.s(cpsStmts))
      appcg(m, m.s[cfsDynLibInit], 
           "if (!($1 = #nimLoadLibrary($2))) #nimLoadLibraryError($2);$n", 
           [tmp, rdLoc(dest)])
      
  if lib.name == nil: internalError("loadDynamicLib")
  
proc mangleDynLibProc(sym: PSym): PRope =
  if sfCompilerProc in sym.flags: 
    # NOTE: sym.loc.r is the external name!
    result = toRope(sym.name.s)
  else:
    result = ropef("Dl_$1", [toRope(sym.id)])
  
proc symInDynamicLib(m: BModule, sym: PSym) = 
  var lib = sym.annex
  let isCall = isGetProcAddr(lib)
  var extname = sym.loc.r
  if not isCall: loadDynamicLib(m, lib)
  if gCmd == cmdCompileToLLVM: incl(sym.loc.flags, lfIndirect)
  var tmp = mangleDynLibProc(sym)
  sym.loc.r = tmp             # from now on we only need the internal name
  sym.typ.sym = nil           # generate a new name
  inc(m.labels, 2)
  if isCall:
    let n = lib.path
    var a: TLoc
    initLocExpr(m.initProc, n[0], a)
    var params = con(rdLoc(a), "(")
    for i in 1 .. n.len-2:
      initLocExpr(m.initProc, n[i], a)
      params.app(rdLoc(a))
      params.app(", ")
    let load = ropef("\t$1 = ($2) ($3$4));$n",
        [tmp, getTypeDesc(m, sym.typ),
        params, cstringLit(m, m.s[cfsDynLibInit], ropeToStr(extname))])
    var last = lastSon(n)
    if last.kind == nkHiddenStdConv: last = last.sons[1]
    internalAssert(last.kind == nkStrLit)
    let idx = last.strVal
    if idx.len == 0:
      app(m.initProc.s(cpsStmts), load)
    elif idx.len == 1 and idx[0] in {'0'..'9'}:
      app(m.extensionLoaders[idx[0]], load)
    else:
      internalError(sym.info, "wrong index: " & idx)
  else:
    appcg(m, m.s[cfsDynLibInit], 
        "\t$1 = ($2) #nimGetProcAddr($3, $4);$n", 
        [tmp, getTypeDesc(m, sym.typ), 
        lib.name, cstringLit(m, m.s[cfsDynLibInit], ropeToStr(extname))])
  appff(m.s[cfsVars], "$2 $1;$n", 
      "$1 = linkonce global $2 zeroinitializer$n", 
      [sym.loc.r, getTypeDesc(m, sym.loc.t)])

proc varInDynamicLib(m: BModule, sym: PSym) = 
  var lib = sym.annex
  var extname = sym.loc.r
  loadDynamicLib(m, lib)
  incl(sym.loc.flags, lfIndirect)
  var tmp = mangleDynLibProc(sym)
  sym.loc.r = tmp             # from now on we only need the internal name
  inc(m.labels, 2)
  appcg(m, m.s[cfsDynLibInit], 
      "$1 = ($2*) #nimGetProcAddr($3, $4);$n", 
      [tmp, getTypeDesc(m, sym.typ), 
      lib.name, cstringLit(m, m.s[cfsDynLibInit], ropeToStr(extname))])
  appf(m.s[cfsVars], "$2* $1;$n",
      [sym.loc.r, getTypeDesc(m, sym.loc.t)])

proc symInDynamicLibPartial(m: BModule, sym: PSym) =
  sym.loc.r = mangleDynLibProc(sym)
  sym.typ.sym = nil           # generate a new name

proc cgsym(m: BModule, name: string): PRope = 
  var sym = magicsys.getCompilerProc(name)
  if sym != nil: 
    case sym.kind
    of skProc, skMethod, skConverter, skIterators: genProc(m, sym)
    of skVar, skResult, skLet: genVarPrototype(m, sym)
    of skType: discard getTypeDesc(m, sym.typ)
    else: internalError("cgsym: " & name)
  else:
    # we used to exclude the system module from this check, but for DLL
    # generation support this sloppyness leads to hard to detect bugs, so
    # we're picky here for the system module too:
    rawMessage(errSystemNeeds, name)
  result = sym.loc.r
  
proc generateHeaders(m: BModule) = 
  app(m.s[cfsHeaders], tnl & "#include \"nimbase.h\"" & tnl)
  var it = PStrEntry(m.headerFiles.head)
  while it != nil: 
    if it.data[0] notin {'\"', '<'}: 
      appf(m.s[cfsHeaders], "$N#include \"$1\"$N", [toRope(it.data)])
    else: 
      appf(m.s[cfsHeaders], "$N#include $1$N", [toRope(it.data)])
    it = PStrEntry(it.next)

proc retIsNotVoid(s: PSym): bool = 
  result = (s.typ.sons[0] != nil) and not isInvalidReturnType(s.typ.sons[0])

proc initFrame(p: BProc, procname, filename: PRope): PRope =
  discard cgsym(p.module, "nimFrame")
  if p.maxFrameLen > 0:
    discard cgsym(p.module, "TVarSlot")
    result = rfmt(nil, "\tnimfrs($1, $2, $3, $4)$N",
                  procname, filename, p.maxFrameLen.toRope,
                  p.blocks[0].frameLen.toRope)
  else:
    result = rfmt(nil, "\tnimfr($1, $2)$N", procname, filename)

proc deinitFrame(p: BProc): PRope =
  result = rfmt(p.module, "\t#popFrame();$n")

proc closureSetup(p: BProc, prc: PSym) =
  if tfCapturesEnv notin prc.typ.flags: return
  # prc.ast[paramsPos].last contains the type we're after:
  var ls = lastSon(prc.ast[paramsPos])
  if ls.kind != nkSym:
    internalError(prc.info, "closure generation failed")
  var env = ls.sym
  #echo "created environment: ", env.id, " for ", prc.name.s
  assignLocalVar(p, env)
  # generate cast assignment:
  linefmt(p, cpsStmts, "$1 = ($2) ClEnv;$n",
          rdLoc(env.loc), getTypeDesc(p.module, env.typ))

proc genProcAux(m: BModule, prc: PSym) =
  var p = newProc(prc, m)
  var header = genProcHeader(m, prc)
  var returnStmt: PRope = nil
  assert(prc.ast != nil)
  if sfPure notin prc.flags and prc.typ.sons[0] != nil:
    if resultPos >= prc.ast.len:
      internalError(prc.info, "proc has no result symbol")
    var res = prc.ast.sons[resultPos].sym # get result symbol
    if not isInvalidReturnType(prc.typ.sons[0]):
      if sfNoInit in prc.flags: incl(res.flags, sfNoInit)
      # declare the result symbol:
      assignLocalVar(p, res)
      assert(res.loc.r != nil)
      returnStmt = rfmt(nil, "\treturn $1;$n", rdLoc(res.loc))
      initLocalVar(p, res, immediateAsgn=false)
    else:
      fillResult(res)
      assignParam(p, res)
      if skipTypes(res.typ, abstractInst).kind == tyArray: 
        incl(res.loc.flags, lfIndirect)
        res.loc.s = OnUnknown
    
  for i in countup(1, sonsLen(prc.typ.n) - 1): 
    var param = prc.typ.n.sons[i].sym
    if param.typ.isCompileTimeOnly: continue
    assignParam(p, param)
  closureSetup(p, prc)
  genStmts(p, prc.getBody) # modifies p.locals, p.init, etc.
  var generatedProc: PRope
  if sfPure in prc.flags:
    if hasNakedDeclspec in extccomp.CC[extccomp.cCompiler].props:
      header = con("__declspec(naked) ", header)
    generatedProc = rfmt(nil, "$N$1 {$n$2$3$4}$N$N",
                         header, p.s(cpsLocals), p.s(cpsInit), p.s(cpsStmts))
  else:
    generatedProc = rfmt(nil, "$N$1 {$N", header)
    app(generatedProc, initGCFrame(p))
    if optStackTrace in prc.options: 
      app(generatedProc, p.s(cpsLocals))
      var procname = cstringLit(p, generatedProc, prc.name.s)
      app(generatedProc, initFrame(p, procname, prc.info.quotedFilename))
    else: 
      app(generatedProc, p.s(cpsLocals))
    if (optProfiler in prc.options) and (gCmd != cmdCompileToLLVM):
      # invoke at proc entry for recursion:
      appcg(p, cpsInit, "\t#nimProfile();$n", [])
    app(generatedProc, p.s(cpsInit))
    app(generatedProc, p.s(cpsStmts))
    if p.beforeRetNeeded: app(generatedProc, ~"\tBeforeRet: ;$n")
    app(generatedProc, deinitGCFrame(p))
    if optStackTrace in prc.options: app(generatedProc, deinitFrame(p))
    app(generatedProc, returnStmt)
    app(generatedProc, ~"}$N")
  app(m.s[cfsProcs], generatedProc)
  
proc genProcPrototype(m: BModule, sym: PSym) = 
  useHeader(m, sym)
  if lfNoDecl in sym.loc.flags: return 
  if lfDynamicLib in sym.loc.flags:
    if getModule(sym).id != m.module.id and
        not containsOrIncl(m.declaredThings, sym.id): 
      app(m.s[cfsVars], rfmt(nil, "extern $1 $2;$n",
                        getTypeDesc(m, sym.loc.t), mangleDynLibProc(sym)))
      if gCmd == cmdCompileToLLVM: incl(sym.loc.flags, lfIndirect)
  elif not containsOrIncl(m.declaredProtos, sym.id):
    var header = genProcHeader(m, sym)
    if sfPure in sym.flags and hasNakedAttribute in CC[cCompiler].props:
      header.app(" __attribute__((naked))")
    app(m.s[cfsProcHeaders], rfmt(nil, "$1;$n", header))

proc genProcNoForward(m: BModule, prc: PSym) = 
  fillProcLoc(prc)
  useHeader(m, prc)
  if lfImportCompilerProc in prc.loc.flags:
    # dependency to a compilerproc:
    discard cgsym(m, prc.name.s)
    return  
  genProcPrototype(m, prc)
  if lfNoDecl in prc.loc.flags: discard
  elif prc.typ.callConv == ccInline:
    # We add inline procs to the calling module to enable C based inlining.
    # This also means that a check with ``q.declaredThings`` is wrong, we need
    # a check for ``m.declaredThings``.
    if not containsOrIncl(m.declaredThings, prc.id): genProcAux(m, prc)
  elif lfDynamicLib in prc.loc.flags:
    var q = findPendingModule(m, prc)
    if q != nil and not containsOrIncl(q.declaredThings, prc.id): 
      symInDynamicLib(q, prc)
    else:
      symInDynamicLibPartial(m, prc)
  elif sfImportc notin prc.flags:
    var q = findPendingModule(m, prc)
    if q != nil and not containsOrIncl(q.declaredThings, prc.id): 
      genProcAux(q, prc)

proc requestConstImpl(p: BProc, sym: PSym) =
  var m = p.module
  useHeader(m, sym)
  if sym.loc.k == locNone:
    fillLoc(sym.loc, locData, sym.typ, mangleName(sym), OnUnknown)
  if lfNoDecl in sym.loc.flags: return
  # declare implementation:
  var q = findPendingModule(m, sym)
  if q != nil and not containsOrIncl(q.declaredThings, sym.id):
    assert q.initProc.module == q
    appf(q.s[cfsData], "NIM_CONST $1 $2 = $3;$n",
        [getTypeDesc(q, sym.typ), sym.loc.r, genConstExpr(q.initProc, sym.ast)])
  # declare header:
  if q != m and not containsOrIncl(m.declaredThings, sym.id):
    assert(sym.loc.r != nil)
    let headerDecl = ropef("extern NIM_CONST $1 $2;$n",
        [getTypeDesc(m, sym.loc.t), sym.loc.r])
    app(m.s[cfsData], headerDecl)
    if sfExportc in sym.flags and generatedHeader != nil:
      app(generatedHeader.s[cfsData], headerDecl)

proc isActivated(prc: PSym): bool = prc.typ != nil

proc genProc(m: BModule, prc: PSym) = 
  if sfBorrow in prc.flags or not isActivated(prc): return
  fillProcLoc(prc)
  if sfForward in prc.flags: addForwardedProc(m, prc)
  else:
    genProcNoForward(m, prc)
    if {sfExportc, sfCompilerProc} * prc.flags == {sfExportc} and
        generatedHeader != nil and lfNoDecl notin prc.loc.flags:
      genProcPrototype(generatedHeader, prc)
      if prc.typ.callConv == ccInline:
        if not containsOrIncl(generatedHeader.declaredThings, prc.id): 
          genProcAux(generatedHeader, prc)

proc genVarPrototypeAux(m: BModule, sym: PSym) = 
  assert(sfGlobal in sym.flags)
  useHeader(m, sym)
  fillLoc(sym.loc, locGlobalVar, sym.typ, mangleName(sym), OnHeap)
  if (lfNoDecl in sym.loc.flags) or containsOrIncl(m.declaredThings, sym.id): 
    return 
  if sym.owner.id != m.module.id: 
    # else we already have the symbol generated!
    assert(sym.loc.r != nil)
    if sfThread in sym.flags: 
      declareThreadVar(m, sym, true)
    else:
      app(m.s[cfsVars], "extern ")
      app(m.s[cfsVars], getTypeDesc(m, sym.loc.t))
      if lfDynamicLib in sym.loc.flags: app(m.s[cfsVars], "*")
      if sfRegister in sym.flags: app(m.s[cfsVars], " register")
      if sfVolatile in sym.flags: app(m.s[cfsVars], " volatile")
      appf(m.s[cfsVars], " $1;$n", [sym.loc.r])

proc genVarPrototype(m: BModule, sym: PSym) =
  genVarPrototypeAux(m, sym)

proc addIntTypes(result: var PRope) {.inline.} =
  appf(result, "#define NIM_INTBITS $1", [
    platform.CPU[targetCPU].intSize.toRope])

proc getCopyright(cfilenoext: string): PRope =
  if optCompileOnly in gGlobalOptions:
    result = ropeff("/* Generated by Nimrod Compiler v$1 */$N" &
        "/*   (c) 2014 Andreas Rumpf */$N" &
        "/* The generated code is subject to the original license. */$N",
        "; Generated by Nimrod Compiler v$1$N" &
        ";   (c) 2012 Andreas Rumpf$N", [toRope(VersionAsString)])
  else:
    result = ropeff("/* Generated by Nimrod Compiler v$1 */$N" &
        "/*   (c) 2014 Andreas Rumpf */$N" &
        "/* The generated code is subject to the original license. */$N" &
        "/* Compiled for: $2, $3, $4 */$N" &
        "/* Command for C compiler:$n   $5 */$N",
        "; Generated by Nimrod Compiler v$1$N" &
        ";   (c) 2014 Andreas Rumpf$N" &
        "; Compiled for: $2, $3, $4$N" &
        "; Command for LLVM compiler:$N   $5$N", [toRope(VersionAsString),
        toRope(platform.OS[targetOS].name),
        toRope(platform.CPU[targetCPU].name),
        toRope(extccomp.CC[extccomp.cCompiler].name),
        toRope(getCompileCFileCmd(cfilenoext))])

proc getFileHeader(cfilenoext: string): PRope =
  result = getCopyright(cfilenoext)
  addIntTypes(result)

proc genFilenames(m: BModule): PRope =
  discard cgsym(m, "dbgRegisterFilename")
  result = nil
  for i in 0.. <fileInfos.len:
    result.appf("dbgRegisterFilename($1);$N", fileInfos[i].projPath.makeCString)

proc genMainProc(m: BModule) =
  const 
    PreMainBody =
      "\tsystemDatInit();$N" &
      "\tsystemInit();$N" &
      "$1" &
      "$2" &
      "$3" &
      "$4"

    MainProcs =
      "\tNimMain();$N"
    
    MainProcsWithResult =
      MainProcs & "\treturn nim_program_result;$N"

    NimMainBody =
      "N_CDECL(void, NimMain)(void) {$N" &
        "\tPreMain();$N" &
        "$1" &
      "}$N$N"

    PosixNimMain =
      "int cmdCount;$N" &
      "char** cmdLine;$N" &
      "char** gEnv;$N" &
      NimMainBody
  
    PosixCMain =
      "int main(int argc, char** args, char** env) {$N" &
        "\tcmdLine = args;$N" &
        "\tcmdCount = argc;$N" &
        "\tgEnv = env;$N" &
        MainProcsWithResult &
      "}$N$N"
  
    StandaloneCMain =
      "int main(void) {$N" &
        MainProcs &
        "\treturn 0;$N" &
      "}$N$N"
    
    WinNimMain = NimMainBody
    
    WinCMain = "N_STDCALL(int, WinMain)(HINSTANCE hCurInstance, $N" &
      "                        HINSTANCE hPrevInstance, $N" &
      "                        LPSTR lpCmdLine, int nCmdShow) {$N" &
      MainProcsWithResult & "}$N$N"
  
    WinNimDllMain = "N_LIB_EXPORT " & NimMainBody

    WinCDllMain =
      "BOOL WINAPI DllMain(HINSTANCE hinstDLL, DWORD fwdreason, $N" &
      "                    LPVOID lpvReserved) {$N" &
      "\tif(fwdreason == DLL_PROCESS_ATTACH) {$N" & MainProcs & "}$N" &
      "\treturn 1;$N}$N$N"

    PosixNimDllMain = WinNimDllMain
    
    PosixCDllMain =
      "void NIM_POSIX_INIT NimMainInit(void) {$N" &
        MainProcs &
      "}$N$N"

  var nimMain, otherMain: TFormatStr
  if platform.targetOS == osWindows and
      gGlobalOptions * {optGenGuiApp, optGenDynLib} != {}: 
    if optGenGuiApp in gGlobalOptions: 
      nimMain = WinNimMain
      otherMain = WinCMain
    else: 
      nimMain = WinNimDllMain
      otherMain = WinCDllMain
    discard lists.includeStr(m.headerFiles, "<windows.h>")
  elif optGenDynLib in gGlobalOptions:
    nimMain = PosixNimDllMain
    otherMain = PosixCDllMain
  elif platform.targetOS == osStandalone:
    nimMain = PosixNimMain
    otherMain = StandaloneCMain
  else:
    nimMain = PosixNimMain
    otherMain = PosixCMain
  if gBreakpoints != nil: discard cgsym(m, "dbgRegisterBreakpoint")
  if optEndb in gOptions:
    gBreakpoints.app(m.genFilenames)
  
  let initStackBottomCall = if emulatedThreadVars() or
                              platform.targetOS == osStandalone: "".toRope
                            else: ropecg(m, "\t#initStackBottom();$N")
  inc(m.labels)
  appcg(m, m.s[cfsProcs], "void PreMain() {$N" & PreMainBody & "}$N$N", [
    mainDatInit, initStackBottomCall, gBreakpoints, otherModsInit])

  appcg(m, m.s[cfsProcs], nimMain, [mainModInit, toRope(m.labels)])
  if optNoMain notin gGlobalOptions:
    appcg(m, m.s[cfsProcs], otherMain, [])

proc getSomeInitName(m: PSym, suffix: string): PRope =
  assert m.kind == skModule
  assert m.owner.kind == skPackage
  if {sfSystemModule, sfMainModule} * m.flags == {}:
    result = m.owner.name.s.mangle.toRope
  result.app m.name.s
  result.app suffix
  
proc getInitName(m: PSym): PRope = getSomeInitName(m, "Init")
proc getDatInitName(m: PSym): PRope = getSomeInitName(m, "DatInit")

proc registerModuleToMain(m: PSym) = 
  var
    init = m.getInitName
    datInit = m.getDatInitName
  appff(mainModProcs, "N_NOINLINE(void, $1)(void);$N",
                      "declare void $1() noinline$N", [init])
  appff(mainModProcs, "N_NOINLINE(void, $1)(void);$N",
                      "declare void $1() noinline$N", [datInit])
  if sfSystemModule notin m.flags:
    appff(mainDatInit, "\t$1();$N", "call void ()* $1$n", [datInit])
    let initCall = ropeff("\t$1();$N", "call void ()* $1$n", [init])
    if sfMainModule in m.flags:
      app(mainModInit, initCall)
    else:
      app(otherModsInit, initCall)
    
proc genInitCode(m: BModule) = 
  var initname = getInitName(m.module)
  var prc = ropeff("N_NOINLINE(void, $1)(void) {$N", 
                   "define void $1() noinline {$n", [initname])
  if m.typeNodes > 0: 
    appcg(m, m.s[cfsTypeInit1], "static #TNimNode $1[$2];$n", 
          [m.typeNodesName, toRope(m.typeNodes)])
  if m.nimTypes > 0: 
    appcg(m, m.s[cfsTypeInit1], "static #TNimType $1[$2];$n", 
          [m.nimTypesName, toRope(m.nimTypes)])
  
  app(prc, initGCFrame(m.initProc))
 
  app(prc, genSectionStart(cpsLocals))
  app(prc, m.preInitProc.s(cpsLocals))
  app(prc, m.initProc.s(cpsLocals))
  app(prc, m.postInitProc.s(cpsLocals))
  app(prc, genSectionEnd(cpsLocals))

  if optStackTrace in m.initProc.options and not m.frameDeclared:
    # BUT: the generated init code might depend on a current frame, so
    # declare it nevertheless:
    m.frameDeclared = true
    if not m.preventStackTrace:
      var procname = cstringLit(m.initProc, prc, m.module.name.s)
      app(prc, initFrame(m.initProc, procname, m.module.info.quotedFilename))
    else:
      app(prc, ~"\tTFrame F; F.len = 0;$N")
    
  app(prc, genSectionStart(cpsInit))
  app(prc, m.preInitProc.s(cpsInit))
  app(prc, m.initProc.s(cpsInit))
  app(prc, m.postInitProc.s(cpsInit))
  app(prc, genSectionEnd(cpsInit))

  app(prc, genSectionStart(cpsStmts))
  app(prc, m.preInitProc.s(cpsStmts))
  app(prc, m.initProc.s(cpsStmts))
  app(prc, m.postInitProc.s(cpsStmts))
  app(prc, genSectionEnd(cpsStmts))
  if optStackTrace in m.initProc.options and not m.preventStackTrace:
    app(prc, deinitFrame(m.initProc))
  app(prc, deinitGCFrame(m.initProc))
  appf(prc, "}$N$N")

  prc.appff("N_NOINLINE(void, $1)(void) {$N",
            "define void $1() noinline {$n", [getDatInitName(m.module)])

  for i in cfsTypeInit1..cfsDynLibInit:
    app(prc, genSectionStart(i))
    app(prc, m.s[i])
    app(prc, genSectionEnd(i))
  
  appf(prc, "}$N$N")
  # we cannot simply add the init proc to ``m.s[cfsProcs]`` anymore because
  # that would lead to a *nesting* of merge sections which the merger does
  # not support. So we add it to another special section: ``cfsInitProc``
  app(m.s[cfsInitProc], prc)
  
  for i, el in pairs(m.extensionLoaders):
    if el != nil:
      let ex = ropef("N_NIMCALL(void, nimLoadProcs$1)(void) {$2}$N$N",
        (i.ord - '0'.ord).toRope, el)
      app(m.s[cfsInitProc], ex)

proc genModule(m: BModule, cfilenoext: string): PRope = 
  result = getFileHeader(cfilenoext)
  result.app(genMergeInfo(m))
  
  generateHeaders(m)

  generateThreadLocalStorage(m)
  for i in countup(cfsHeaders, cfsProcs): 
    app(result, genSectionStart(i))
    app(result, m.s[i])
    app(result, genSectionEnd(i))
  app(result, m.s[cfsInitProc])

proc newPreInitProc(m: BModule): BProc =
  result = newProc(nil, m)
  # little hack so that unique temporaries are generated:
  result.labels = 100_000

proc newPostInitProc(m: BModule): BProc =
  result = newProc(nil, m)
  # little hack so that unique temporaries are generated:
  result.labels = 200_000

proc initProcOptions(m: BModule): TOptions = 
  if sfSystemModule in m.module.flags: gOptions-{optStackTrace} else: gOptions

proc rawNewModule(module: PSym, filename: string): BModule =
  new(result)
  initLinkedList(result.headerFiles)
  result.declaredThings = initIntSet()
  result.declaredProtos = initIntSet()
  result.cfilename = filename
  result.filename = filename
  initIdTable(result.typeCache)
  initIdTable(result.forwTypeCache)
  result.module = module
  result.typeInfoMarker = initIntSet()
  result.initProc = newProc(nil, result)
  result.initProc.options = initProcOptions(result)
  result.preInitProc = newPreInitProc(result)
  result.postInitProc = newPostInitProc(result)
  initNodeTable(result.dataCache)
  result.typeStack = @[]
  result.forwardedProcs = @[]
  result.typeNodesName = getTempName()
  result.nimTypesName = getTempName()
  # no line tracing for the init sections of the system module so that we
  # don't generate a TFrame which can confuse the stack botton initialization:
  if sfSystemModule in module.flags:
    result.preventStackTrace = true
    excl(result.preInitProc.options, optStackTrace)
    excl(result.postInitProc.options, optStackTrace)

proc nullify[T](arr: var T) =
  for i in low(arr)..high(arr):
    arr[i] = nil

proc resetModule*(m: BModule) =
  # between two compilations in CAAS mode, we can throw
  # away all the data that was written to disk
  initLinkedList(m.headerFiles)
  m.declaredProtos = initIntSet()
  initIdTable(m.forwTypeCache)
  m.initProc = newProc(nil, m)
  m.initProc.options = initProcOptions(m)
  m.preInitProc = newPreInitProc(m)
  m.postInitProc = newPostInitProc(m)
  initNodeTable(m.dataCache)
  m.typeStack = @[]
  m.forwardedProcs = @[]
  m.typeNodesName = getTempName()
  m.nimTypesName = getTempName()
  m.preventStackTrace = sfSystemModule in m.module.flags
  nullify m.s
  m.usesThreadVars = false
  m.typeNodes = 0
  m.nimTypes = 0
  nullify m.extensionLoaders
  
  # indicate that this is now cached module
  # the cache will be invalidated by nullifying gModules
  m.fromCache = true
  
  # we keep only the "merge info" information for the module
  # and the properties that can't change:
  # m.filename
  # m.cfilename
  # m.isHeaderFile
  # m.module ?
  # m.typeCache
  # m.declaredThings
  # m.typeInfoMarker
  # m.labels
  # m.FrameDeclared

proc resetCgenModules* =
  for m in cgenModules(): resetModule(m)

proc rawNewModule(module: PSym): BModule =
  result = rawNewModule(module, module.position.int32.toFullPath)

proc newModule(module: PSym): BModule =
  # we should create only one cgen module for each module sym
  internalAssert getCgenModule(module) == nil

  result = rawNewModule(module)
  growCache gModules, module.position
  gModules[module.position] = result

  if (optDeadCodeElim in gGlobalOptions): 
    if (sfDeadCodeElim in module.flags): 
      internalError("added pending module twice: " & module.filename)

proc myOpen(module: PSym): PPassContext = 
  result = newModule(module)
  if optGenIndex in gGlobalOptions and generatedHeader == nil:
    let f = if headerFile.len > 0: headerFile else: gProjectFull
    generatedHeader = rawNewModule(module,
      changeFileExt(completeCFilePath(f), hExt))
    generatedHeader.isHeaderFile = true

proc writeHeader(m: BModule) =
  var result = getCopyright(m.filename)
  var guard = ropef("__$1__", m.filename.splitFile.name.toRope)
  result.appf("#ifndef $1$n#define $1$n", guard)
  addIntTypes(result)
  generateHeaders(m)

  generateThreadLocalStorage(m)
  for i in countup(cfsHeaders, cfsProcs): 
    app(result, genSectionStart(i))
    app(result, m.s[i])
    app(result, genSectionEnd(i))
  app(result, m.s[cfsInitProc])
  
  if optGenDynLib in gGlobalOptions:
    result.app("N_LIB_IMPORT ")
  result.appf("N_CDECL(void, NimMain)(void);$n")
  result.appf("#endif /* $1 */$n", guard)
  writeRope(result, m.filename)

proc getCFile(m: BModule): string =
  result = changeFileExt(completeCFilePath(m.cfilename.withPackageName), cExt)

proc myOpenCached(module: PSym, rd: PRodReader): PPassContext =
  assert optSymbolFiles in gGlobalOptions
  var m = newModule(module)
  readMergeInfo(getCFile(m), m)
  result = m

proc myProcess(b: PPassContext, n: PNode): PNode = 
  result = n
  if b == nil or passes.skipCodegen(n): return
  var m = BModule(b)
  m.initProc.options = initProcOptions(m)
  genStmts(m.initProc, n)

proc finishModule(m: BModule) = 
  var i = 0
  while i <= high(m.forwardedProcs): 
    # Note: ``genProc`` may add to ``m.forwardedProcs``, so we cannot use
    # a ``for`` loop here
    var prc = m.forwardedProcs[i]
    if sfForward in prc.flags: 
      internalError(prc.info, "still forwarded: " & prc.name.s)
    genProcNoForward(m, prc)
    inc(i)
  assert(gForwardedProcsCounter >= i)
  dec(gForwardedProcsCounter, i)
  setLen(m.forwardedProcs, 0)

proc shouldRecompile(code: PRope, cfile, cfilenoext: string): bool = 
  result = true
  if optForceFullMake notin gGlobalOptions:
    var objFile = toObjFile(cfilenoext)
    if writeRopeIfNotEqual(code, cfile): return 
    if existsFile(objFile) and os.fileNewer(objFile, cfile): result = false
  else: 
    writeRope(code, cfile)

# We need 2 different logics here: pending modules (including
# 'nim__dat') may require file merging for the combination of dead code
# elimination and incremental compilation! Non pending modules need no
# such logic and in fact the logic hurts for the main module at least;
# it would generate multiple 'main' procs, for instance.

proc writeModule(m: BModule, pending: bool) =
  # generate code for the init statements of the module:
  var cfile = getCFile(m)
  var cfilenoext = changeFileExt(cfile, "")
  
  if not m.fromCache or optForceFullMake in gGlobalOptions:
    genInitCode(m)
    finishTypeDescriptions(m)
    if sfMainModule in m.module.flags: 
      # generate main file:
      app(m.s[cfsProcHeaders], mainModProcs)
      generateThreadVarsSize(m)
    
    var code = genModule(m, cfilenoext)
    when hasTinyCBackend:
      if gCmd == cmdRun:
        tccgen.compileCCode(ropeToStr(code))
        return

    if shouldRecompile(code, cfile, cfilenoext):
      addFileToCompile(cfilenoext)
  elif pending and mergeRequired(m) and sfMainModule notin m.module.flags:
    mergeFiles(cfile, m)
    genInitCode(m)
    finishTypeDescriptions(m)
    var code = genModule(m, cfilenoext)
    writeRope(code, cfile)
    addFileToCompile(cfilenoext)
  elif not existsFile(toObjFile(cfilenoext)):
    # Consider: first compilation compiles ``system.nim`` and produces
    # ``system.c`` but then compilation fails due to an error. This means
    # that ``system.o`` is missing, so we need to call the C compiler for it:
    addFileToCompile(cfilenoext)
  
  addFileToLink(cfilenoext)

proc updateCachedModule(m: BModule) =
  let cfile = getCFile(m)
  let cfilenoext = changeFileExt(cfile, "")
  
  if mergeRequired(m) and sfMainModule notin m.module.flags:
    mergeFiles(cfile, m)
    genInitCode(m)
    finishTypeDescriptions(m)
    var code = genModule(m, cfilenoext)
    writeRope(code, cfile)
    addFileToCompile(cfilenoext)

  addFileToLink(cfilenoext)

proc myClose(b: PPassContext, n: PNode): PNode = 
  result = n
  if b == nil or passes.skipCodegen(n): return 
  var m = BModule(b)
  if n != nil: 
    m.initProc.options = initProcOptions(m)
    genStmts(m.initProc, n)
  # cached modules need to registered too: 
  registerModuleToMain(m.module)

  if sfMainModule in m.module.flags: 
    var disp = generateMethodDispatchers()
    for i in 0..sonsLen(disp)-1: genProcAux(m, disp.sons[i].sym)
    genMainProc(m)

proc cgenWriteModules* =
  # we need to process the transitive closure because recursive module
  # deps are allowed (and the system module is processed in the wrong
  # order anyway)
  if generatedHeader != nil: finishModule(generatedHeader)
  while gForwardedProcsCounter > 0:
    for m in cgenModules():
      if not m.fromCache:
        finishModule(m)
  for m in cgenModules():
    if m.fromCache:
      m.updateCachedModule
    else:
      m.writeModule(pending=true)
  writeMapping(gMapping)
  if generatedHeader != nil: writeHeader(generatedHeader)

const cgenPass* = makePass(myOpen, myOpenCached, myProcess, myClose)