Macro causes compile error from gcc

[rehartmann]

The following code:

import macros

type
   Expression* = ref object of RootObj

   StringExpression = ref object of Expression
      value: string

   BooleanExpression = ref object of Expression
      value: bool

   OpExpression = ref object of Expression
     name: string
     args: seq[Expression]

   AssignmentKind = enum
     akCopy, akInsert, akUpdate, akDelete

   AttrUpdate* = object
     name: string
     exp: Expression

   Assignment* = ref object
     case kind: AssignmentKind
     of akCopy:
       copyDest: string
     of akInsert:
       insertDest: string
       insertFlags: int
     of akUpdate:
       updateDest: string
       updateCond: Expression
       attrUpdates: seq[AttrUpdate]
     of akDelete:
       deleteDest: string
       deleteCond: Expression

proc toExpr(s: string): Expression =
  ## Converts a string value to an expression.
  return StringExpression(value: s)

proc toExpr(b: bool): Expression =
  return BooleanExpression(value: b)

proc updateAssignment(tbName: string, cond: Expression,
                 attrUpdates: varargs[AttrUpdate]): Assignment =
  result = new Assignment
  result.kind = akUpdate
  result.updateDest = tbName
  result.updateCond = cond

  result.attrUpdates = newSeq[AttrUpdate](attrUpdates.len)
  for i in 0..<result.attrUpdates.len:
    result.attrUpdates[i] = attrUpdates[i]

macro myUpdate(dest: untyped, cond: Expression,
              assigns: varargs[AttrUpdate]): Assignment =
  result = newCall("updateAssignment", toStrLit(dest), cond, assigns)

proc attributeAssignment(dest: string, src: Expression): AttrUpdate =
  result.name = dest
  result.exp = src

macro `:=`(dest: untyped, src: Expression): AttrUpdate =
  result = newCall("attributeAssignment", toStrLit(dest), src)

proc assign*(assigns: varargs[Assignment]) =
  return

assign(myUpdate(t3, toExpr(true), s := toExpr("Bar")))

causes the following error when compiling:

Error: execution of an external compiler program 'gcc -c  -w  -I/usr/lib/nim -o /home/rene/projects/nidurodb/test/nimcache/assigntest.o /home/rene/projects/nidurodb/test/nimcache/assigntest.c' failed with exit code: 1

/home/rene/projects/nidurodb/test/nimcache/assigntest.c: In function ‘NimMainModule’:
/home/rene/projects/nidurodb/test/nimcache/assigntest.c:687:112: error: ‘T3_Len_0’ undeclared (first use in this function)
  T1_[0] = updateAssignment_W9aVjf64l6HNbKHPkoTWOgA(((NimStringDesc*) &TM_rFCIiNhfswqwZJUDLErU2g_13), T2_, T3_, T3_Len_0);
                                                                                                                ^~~~~~~~
/home/rene/projects/nidurodb/test/nimcache/assigntest.c:687:112: note: each undeclared identifier is reported only once for each function it appears in

[rehartmann]

The problem disappears if the definition of myUpdate is changed to:

macro myUpdate*(dest: untyped, cond: Expression,
              attrUpdates: varargs[AttrUpdate]): Assignment =
  var updateAssignmentArgs: seq[NimNode] = @[toStrLit(dest), cond]
  for attrUpdate in attrUpdates:
    updateAssignmentArgs.add(attrUpdate)
  result = newCall("updateAssignment", updateAssignmentArgs)

[krux02]

Please elaborate a bit on what you are trying to do and what might cause the crash. Also please try to boil the code down to what is causing the crash.

[rehartmann]

The reason is probably that myUpdate() passes its arguments directly to newCall(), instead of passing them as NimNodes. But this should result in an compile error rather than invalid C code being generated.

[stale[bot]]

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