make the build more robust

compiler/ccgexprs.nim

@@ -909,9 +909,14 @@ proc genSeqElem(p: BProc, n, x, y: PNode, d: var TLoc) =
   if ty.kind in {tyRef, tyPtr}:
     ty = skipTypes(ty.lastSon, abstractVarRange) # emit range check:
   if optBoundsCheck in p.options:
-    linefmt(p, cpsStmts,
-          "if (!$2 || (NU)($1) >= (NU)($2->$3)) #raiseIndexError();$n",
-          rdLoc(b), rdLoc(a), lenField(p))
+    if ty.kind == tyString and not defined(nimNoZeroTerminator):
+      linefmt(p, cpsStmts,
+              "if (!$2 || (NU)($1) > (NU)($2->$3)) #raiseIndexError();$n",
+              rdLoc(b), rdLoc(a), lenField(p))
+    else:
+      linefmt(p, cpsStmts,
+              "if (!$2 || (NU)($1) >= (NU)($2->$3)) #raiseIndexError();$n",
+              rdLoc(b), rdLoc(a), lenField(p))
   if d.k == locNone: d.storage = OnHeap
   if skipTypes(a.t, abstractVar).kind in {tyRef, tyPtr}:
     a.r = rfmt(nil, "(*$1)", a.r)

compiler/condsyms.nim

@@ -115,3 +115,4 @@ proc initDefines*() =
   defineSymbol("nimSymKind")
   defineSymbol("nimVmEqIdent")
   defineSymbol("nimNoNil")
+  defineSymbol("nimNoZeroTerminator")