the mainmodule option has effect only when no explicit module is given

compiler/commands.nim

@@ -231,8 +231,7 @@ proc processSwitch(switch, arg: string, pass: TCmdlinePass, info: TLineInfo) =
     options.outFile = arg
   of "mainmodule", "m":
     expectArg(switch, arg, pass, info)
-    gProjectName = arg
+    optMainModule = arg
-    gProjectFull = gProjectPath / gProjectName
   of "define", "d": 
     expectArg(switch, arg, pass, info)
     DefineSymbol(arg)

compiler/main.nim

@@ -382,15 +382,14 @@ proc CommandSuggest =
 
 proc wantMainModule =
   if gProjectFull.len == 0:
+    if optMainModule.len == 0:
       Fatal(gCmdLineInfo, errCommandExpectsFilename)
+    else:
+      gProjectName = optMainModule
+      gProjectFull = gProjectPath / gProjectName
+
   gProjectMainIdx = addFileExt(gProjectFull, nimExt).fileInfoIdx
 
-var oss: PGenericSeq
-proc dbgseqimp(x: PGenericSeq) {.cdecl.} =
-  oss = x
-
-seqdbg = dbgseqimp
-
 proc resetMemory =
   resetCompilationLists()
   ccgutils.resetCaches()

compiler/options.nim

@@ -99,7 +99,7 @@ var
   gVerbosity*: int            # how verbose the compiler is
   gNumberOfProcessors*: int   # number of processors
   gWholeProject*: bool # for 'doc2': output any dependency
-  gEvalExpr*: string          # expression for idetools --eval
+  gEvalExpr* = ""             # expression for idetools --eval
   gLastCmdTime*: float        # when caas is enabled, we measure each command
   gListFullPaths*: bool
   
@@ -124,6 +124,7 @@ var
   gProjectPath* = "" # holds a path like /home/alice/projects/nimrod/compiler/
   gProjectFull* = "" # projectPath/projectName
   gProjectMainIdx*: int32 # the canonical path id of the main module
+  optMainModule* = "" # the main module that should be used for idetools commands
   nimcacheDir* = ""
   command* = "" # the main command (e.g. cc, check, scan, etc)
   commandArgs*: seq[string] = @[] # any arguments after the main command

lib/system/gc.nim

@@ -81,7 +81,7 @@ const
     # examined in the decref loop in collectCycles.
     # XXX: not implemented yet as tests didn't show any improvement from this
    
-  MarkingSkipsAcyclicObjects = false
+  MarkingSkipsAcyclicObjects = true
     # Acyclic objects can be safely ignored in the mark and scan phases, 
     # because they cannot contribute to the internal count.
     # XXX: if we generate specialized `markCyclic` and `markAcyclic`

tests/reject/tenummix.nim

@@ -1,6 +1,6 @@
 discard """
   file: "system.nim"
-  line: 669
+  line: 670
   errormsg: "type mismatch"
 """