Merge pull request #7967 from nitely/empty_openarray_7904

support empty toOpenArray

compiler/ccgcalls.nim

@@ -83,7 +83,7 @@ proc isInCurrentFrame(p: BProc, n: PNode): bool =
     result = isInCurrentFrame(p, n.sons[0])
   else: discard
 
-proc genIndexCheck(p: BProc; arr, idx: TLoc)
+proc genBoundsCheck(p: BProc; arr, a, b: TLoc)
 
 proc openArrayLoc(p: BProc, n: PNode): Rope =
   var a: TLoc
@@ -97,8 +97,7 @@ proc openArrayLoc(p: BProc, n: PNode): Rope =
     initLocExpr(p, q[3], c)
     # but first produce the required index checks:
     if optBoundsCheck in p.options:
-      genIndexCheck(p, a, b)
+      genBoundsCheck(p, a, b, c)
-      genIndexCheck(p, a, c)
     let ty = skipTypes(a.t, abstractVar+{tyPtr})
     case ty.kind
     of tyArray:

compiler/ccgexprs.nim

@@ -873,21 +873,26 @@ proc genCStringElem(p: BProc, n, x, y: PNode, d: var TLoc) =
   putIntoDest(p, d, n,
               ropecg(p.module, "$1[$2]", rdLoc(a), rdCharLoc(b)), a.storage)
 
-proc genIndexCheck(p: BProc; arr, idx: TLoc) =
+proc genBoundsCheck(p: BProc; arr, a, b: TLoc) =
   let ty = skipTypes(arr.t, abstractVarRange)
   case ty.kind
   of tyOpenArray, tyVarargs:
-    linefmt(p, cpsStmts, "if ((NU)($1) >= (NU)($2Len_0)) #raiseIndexError();$n",
+    linefmt(p, cpsStmts,
-            rdLoc(idx), rdLoc(arr))
+      "if ($2-$1 != -1 && " &
+      "((NU)($1) >= (NU)($3Len_0) || (NU)($2) >= (NU)($3Len_0))) #raiseIndexError();$n",
+      rdLoc(a), rdLoc(b), rdLoc(arr))
   of tyArray:
     let first = intLiteral(firstOrd(ty))
     if tfUncheckedArray notin ty.flags:
-      linefmt(p, cpsStmts, "if ($1 < $2 || $1 > $3) #raiseIndexError();$n",
+      linefmt(p, cpsStmts,
-              rdCharLoc(idx), first, intLiteral(lastOrd(ty)))
+        "if ($2-$1 != -1 && " &
+        "($2-$1 < -1 || $1 < $3 || $1 > $4 || $2 < $3 || $2 > $4)) #raiseIndexError();$n",
+        rdCharLoc(a), rdCharLoc(b), first, intLiteral(lastOrd(ty)))
   of tySequence, tyString:
     linefmt(p, cpsStmts,
-          "if (!$2 || (NU)($1) >= (NU)($2->$3)) #raiseIndexError();$n",
+      "if ($2-$1 != -1 && " &
-          rdLoc(idx), rdLoc(arr), lenField(p))
+      "(!$3 || (NU)($1) >= (NU)($3->$4) || (NU)($2) >= (NU)($3->$4))) #raiseIndexError();$n",
+      rdLoc(a), rdLoc(b), rdLoc(arr), lenField(p))
   else: discard
 
 proc genOpenArrayElem(p: BProc, n, x, y: PNode, d: var TLoc) =

tests/system/tsystem_misc.nim

@@ -11,6 +11,10 @@ discard """
 2
 3
 4
+2
+1
+2
+3
 '''
 """
 
@@ -47,3 +51,38 @@ foo(toOpenArray(arr, 8, 12))
 
 var seqq = @[1, 2, 3, 4, 5]
 foo(toOpenArray(seqq, 1, 3))
+
+# empty openArray issue #7904
+foo(toOpenArray(seqq, 0, -1))
+foo(toOpenArray(seqq, 1, 0))
+doAssertRaises(IndexError):
+  foo(toOpenArray(seqq, 0, -2))
+
+foo(toOpenArray(arr, 9, 8))
+foo(toOpenArray(arr, 0, -1))
+foo(toOpenArray(arr, 1, 0))
+doAssertRaises(IndexError):
+  foo(toOpenArray(arr, 10, 8))
+
+# test openArray of openArray
+proc oaEmpty(a: openArray[int]) =
+  foo(toOpenArray(a, 0, -1))
+
+proc oaFirstElm(a: openArray[int]) =
+  foo(toOpenArray(a, 0, 0))
+
+oaEmpty(toOpenArray(seqq, 0, -1))
+oaEmpty(toOpenArray(seqq, 1, 0))
+oaEmpty(toOpenArray(seqq, 1, 2))
+oaFirstElm(toOpenArray(seqq, 1, seqq.len-1))
+
+var arrNeg: array[-3 .. -1, int] = [1, 2, 3]
+foo(toOpenArray(arrNeg, -3, -1))
+foo(toOpenArray(arrNeg, 0, -1))
+foo(toOpenArray(arrNeg, -3, -4))
+doAssertRaises(IndexError):
+  foo(toOpenArray(arrNeg, -4, -1))
+doAssertRaises(IndexError):
+  foo(toOpenArray(arrNeg, -1, 0))
+doAssertRaises(IndexError):
+  foo(toOpenArray(arrNeg, -1, -3))