diff --git a/compiler/ccgexprs.nim b/compiler/ccgexprs.nim
index 94a6f4781b..39333a80d3 100644
--- a/compiler/ccgexprs.nim
+++ b/compiler/ccgexprs.nim
@@ -484,7 +484,7 @@ proc unaryArithOverflow(p: BProc, e: PNode, d: var TLoc, m: TMagic) =
     opr: array[mUnaryMinusI..mAbsI64, string] = [
       mUnaryMinusI: "((NI$2)-($1))",
       mUnaryMinusI64: "-($1)",
-      mAbsI: "(NI$2)abs($1)",
+      mAbsI: "($1 > 0? ($1) : -($1))",
       mAbsI64: "($1 > 0? ($1) : -($1))"]
   var
     a: TLoc
diff --git a/compiler/cgen.nim b/compiler/cgen.nim
index 8d66d7a3b1..198b1187d8 100644
--- a/compiler/cgen.nim
+++ b/compiler/cgen.nim
@@ -503,7 +503,8 @@ proc assignLocalVar(p: BProc, s: PSym) =
     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: 
+    if sfVolatile in s.flags or (p.nestedTryStmts.len > 0 and
+                                 gCmd != cmdCompileToCpp):
       app(decl, " volatile")
     appf(decl, " $1;$n", [s.loc.r])
   else:
diff --git a/compiler/main.nim b/compiler/main.nim
index f833394f72..b4af49248f 100644
--- a/compiler/main.nim
+++ b/compiler/main.nim
@@ -310,7 +310,7 @@ proc mainCommand* =
   of "cpp", "compiletocpp":
     extccomp.cExt = ".cpp"
     gCmd = cmdCompileToCpp
-    if cCompiler == ccGcc: setCC("gpp")
+    if cCompiler == ccGcc: setCC("gcc")
     wantMainModule()
     defineSymbol("cpp")
     commandCompileToC()
diff --git a/compiler/rodutils.nim b/compiler/rodutils.nim
index 4433ed4abd..09b92cd8ad 100644
--- a/compiler/rodutils.nim
+++ b/compiler/rodutils.nim
@@ -10,7 +10,7 @@
 ## Serialization utilities for the compiler.
 import strutils
 
-proc c_sprintf(buf, frmt: cstring) {.importc: "sprintf", nodecl, varargs.}
+proc c_sprintf(buf, frmt: cstring) {.importc: "sprintf", header: "<stdio.h>", nodecl, varargs.}
 
 proc toStrMaxPrecision*(f: BiggestFloat): string = 
   if f != f:
diff --git a/koch.nim b/koch.nim
index c203e0fd09..4d0ac0254d 100644
--- a/koch.nim
+++ b/koch.nim
@@ -152,7 +152,7 @@ proc boot(args: string) =
   copyExe(findStartNimrod(), 0.thVersion)
   for i in 0..2:
     echo "iteration: ", i+1
-    exec i.thVersion & " cc $# $# compiler" / "nimrod.nim" % [bootOptions, args]
+    exec i.thVersion & " c $# $# compiler" / "nimrod.nim" % [bootOptions, args]
     if sameFileContent(output, i.thVersion):
       copyExe(output, finalDest)
       echo "executables are equal: SUCCESS!"
diff --git a/lib/pure/oids.nim b/lib/pure/oids.nim
index b3e74d2a1a..2843e6c656 100644
--- a/lib/pure/oids.nim
+++ b/lib/pure/oids.nim
@@ -62,9 +62,9 @@ var
 
 proc genOid*(): TOid =
   ## generates a new OID.
-  proc rand(): cint {.importc: "rand", nodecl.}
+  proc rand(): cint {.importc: "rand", header: "<stdlib.h>", nodecl.}
   proc gettime(dummy: ptr cint): cint {.importc: "time", header: "<time.h>".}
-  proc srand(seed: cint) {.importc: "srand", nodecl.}
+  proc srand(seed: cint) {.importc: "srand", header: "<stdlib.h>", nodecl.}
 
   var t = gettime(nil)
   
diff --git a/lib/pure/osproc.nim b/lib/pure/osproc.nim
index 6e250f9d54..d2ada70148 100644
--- a/lib/pure/osproc.nim
+++ b/lib/pure/osproc.nim
@@ -903,7 +903,7 @@ elif not defined(useNimRtl):
       createStream(p.errStream, p.errHandle, fmRead)
     return p.errStream
 
-  proc csystem(cmd: cstring): cint {.nodecl, importc: "system".}
+  proc csystem(cmd: cstring): cint {.nodecl, importc: "system", header: "<stdlib.h>".}
 
   proc execCmd(command: string): int =
     when defined(linux):
diff --git a/lib/system/sets.nim b/lib/system/sets.nim
index 043d375335..794c65cb8e 100644
--- a/lib/system/sets.nim
+++ b/lib/system/sets.nim
@@ -10,7 +10,7 @@
 # set handling
 
 type
-  TNimSet = array [0..4*2048-1, int8]
+  TNimSet = array [0..4*2048-1, uint8]
 
 proc countBits32(n: int32): int {.compilerproc.} =
   var v = n
@@ -25,4 +25,4 @@ proc countBits64(n: int64): int {.compilerproc.} =
 proc cardSet(s: TNimSet, len: int): int {.compilerproc.} =
   result = 0
   for i in countup(0, len-1):
-    inc(result, countBits32(int32(ze(s[i]))))
+    inc(result, countBits32(int32(s[i])))