reduce openArray-related C undefined behavior (#20795)

nim-lang · Nov 9, 2022 · 6894a00 · 6894a00
1 parent 25cb19a
commit 6894a00
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Showing 3 changed files with 25 additions and 10 deletions.
diff --git a/compiler/ccgcalls.nim b/compiler/ccgcalls.nim
@@ -194,10 +194,12 @@ proc genOpenArraySlice(p: BProc; q: PNode; formalType, destType: PType): (Rope,
         optSeqDestructors in p.config.globalOptions:
       linefmt(p, cpsStmts, "#nimPrepareStrMutationV2($1);$n", [byRefLoc(p, a)])
     if atyp.kind in {tyVar} and not compileToCpp(p.module):
-      result = ("($4*)(*$1)$3+($2)" % [rdLoc(a), rdLoc(b), dataField(p), dest],
+      result = ("(($5) ? (($4*)(*$1)$3+($2)) : NIM_NIL)" %
+                  [rdLoc(a), rdLoc(b), dataField(p), dest, dataFieldAccessor(p, "*" & rdLoc(a))],
                 lengthExpr)
     else:
-      result = ("($4*)$1$3+($2)" % [rdLoc(a), rdLoc(b), dataField(p), dest],
+      result = ("(($5) ? (($4*)$1$3+($2)) : NIM_NIL)" %
+                  [rdLoc(a), rdLoc(b), dataField(p), dest, dataFieldAccessor(p, rdLoc(a))],
                 lengthExpr)
   else:
     internalError(p.config, "openArrayLoc: " & typeToString(a.t))
@@ -238,17 +240,22 @@ proc openArrayLoc(p: BProc, formalType: PType, n: PNode; result: var Rope) =
       if ntyp.kind in {tyVar} and not compileToCpp(p.module):
         var t: TLoc
         t.r = "(*$1)" % [a.rdLoc]
-        result.add "(*$1)$3, $2" % [a.rdLoc, lenExpr(p, t), dataField(p)]
+        result.add "($4) ? ((*$1)$3) : NIM_NIL, $2" %
+                     [a.rdLoc, lenExpr(p, t), dataField(p),
+                      dataFieldAccessor(p, "*" & a.rdLoc)]
       else:
-        result.add "$1$3, $2" % [a.rdLoc, lenExpr(p, a), dataField(p)]
+        result.add "($4) ? ($1$3) : NIM_NIL, $2" %
+                     [a.rdLoc, lenExpr(p, a), dataField(p), dataFieldAccessor(p, a.rdLoc)]
     of tyArray:
       result.add "$1, $2" % [rdLoc(a), rope(lengthOrd(p.config, a.t))]
     of tyPtr, tyRef:
       case lastSon(a.t).kind
       of tyString, tySequence:
         var t: TLoc
         t.r = "(*$1)" % [a.rdLoc]
-        result.add "(*$1)$3, $2" % [a.rdLoc, lenExpr(p, t), dataField(p)]
+        result.add "($4) ? ((*$1)$3) : NIM_NIL, $2" %
+                     [a.rdLoc, lenExpr(p, t), dataField(p),
+                      dataFieldAccessor(p, "*" & a.rdLoc)]
       of tyArray:
         result.add "$1, $2" % [rdLoc(a), rope(lengthOrd(p.config, lastSon(a.t)))]
       else:

diff --git a/compiler/ccgexprs.nim b/compiler/ccgexprs.nim
@@ -298,8 +298,8 @@ proc genOpenArrayConv(p: BProc; d: TLoc; a: TLoc) =
       linefmt(p, cpsStmts, "$1.Field0 = $2; $1.Field1 = $2Len_0;$n",
         [rdLoc(d), a.rdLoc])
   of tySequence:
-    linefmt(p, cpsStmts, "$1.Field0 = $2$3; $1.Field1 = $4;$n",
-      [rdLoc(d), a.rdLoc, dataField(p), lenExpr(p, a)])
+    linefmt(p, cpsStmts, "$1.Field0 = ($5) ? ($2$3) : NIM_NIL; $1.Field1 = $4;$n",
+      [rdLoc(d), a.rdLoc, dataField(p), lenExpr(p, a), dataFieldAccessor(p, a.rdLoc)])
   of tyArray:
     linefmt(p, cpsStmts, "$1.Field0 = $2; $1.Field1 = $3;$n",
       [rdLoc(d), rdLoc(a), rope(lengthOrd(p.config, a.t))])
@@ -308,8 +308,8 @@ proc genOpenArrayConv(p: BProc; d: TLoc; a: TLoc) =
     if etyp.kind in {tyVar} and optSeqDestructors in p.config.globalOptions:
       linefmt(p, cpsStmts, "#nimPrepareStrMutationV2($1);$n", [byRefLoc(p, a)])
 
-    linefmt(p, cpsStmts, "$1.Field0 = $2$3; $1.Field1 = $4;$n",
-      [rdLoc(d), a.rdLoc, dataField(p), lenExpr(p, a)])
+    linefmt(p, cpsStmts, "$1.Field0 = ($5) ? ($2$3) : NIM_NIL; $1.Field1 = $4;$n",
+      [rdLoc(d), a.rdLoc, dataField(p), lenExpr(p, a), dataFieldAccessor(p, a.rdLoc)])
   else:
     internalError(p.config, a.lode.info, "cannot handle " & $a.t.kind)
 
@@ -1792,7 +1792,9 @@ proc genRepr(p: BProc, e: PNode, d: var TLoc) =
       putIntoDest(p, b, e, "$1, $1Len_0" % [rdLoc(a)], a.storage)
     of tyString, tySequence:
       putIntoDest(p, b, e,
-                  "$1$3, $2" % [rdLoc(a), lenExpr(p, a), dataField(p)], a.storage)
+                  "($4) ? ($1$3) : NIM_NIL, $2" %
+                    [rdLoc(a), lenExpr(p, a), dataField(p), dataFieldAccessor(p, a.rdLoc)],
+                  a.storage)
     of tyArray:
       putIntoDest(p, b, e,
                   "$1, $2" % [rdLoc(a), rope(lengthOrd(p.config, a.t))], a.storage)

diff --git a/compiler/cgen.nim b/compiler/cgen.nim
@@ -322,6 +322,12 @@ proc lenExpr(p: BProc; a: TLoc): Rope =
   else:
     result = "($1 ? $1->$2 : 0)" % [rdLoc(a), lenField(p)]
 
+proc dataFieldAccessor(p: BProc, sym: Rope): Rope =
+  if optSeqDestructors in p.config.globalOptions:
+    result = "(" & sym & ").p"
+  else:
+    result = sym
+
 proc dataField(p: BProc): Rope =
   if optSeqDestructors in p.config.globalOptions:
     result = rope".p->data"