[Issue 3724] New: bug in Expression::arraySyntaxCopy (null pointer dereference on struct->union->struct

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http://d.puremagic.com/issues/show_bug.cgi?id=3724

           Summary: bug in Expression::arraySyntaxCopy (null pointer
                    dereference on struct->union->struct
           Product: D
           Version: 2.039
          Platform: x86
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody at puremagic.com
        ReportedBy: baryluk at smp.if.uj.edu.pl


--- Comment #0 from Witold Baryluk <baryluk at smp.if.uj.edu.pl> 2010-01-19 19:14:35 PST ---
In case of code similar to this

struct v {
  union {
     struct { float a, b; }
     struct { float c[2]; }
  }
}

(it is more complicated than just this sample, to trigger this bug.
I can't easly produce small example)


file expression.c
method Expression *StructLiteralExp::semantic(Scope *sc)
performs kind of flatening, and adds member c to array "elements",
but in case on union memberrs it adds them as null:
relevant lines:
line 3373
 if (v->offset < offset)
 {   e = NULL;
     sd->hasUnions = 1;
 }


and line 3393
  elements->push(e)


Fix:
In file expression.c line 1477
method Expressions *Expression::arraySyntaxCopy(Expressions *exps)
add condition:

 for (int i = 0; i < a->dim; i++)
 {   Expression *e = (Expression *)exps->data[i];
-    e = e->syntaxCopy();
+   if (e)
+        e = e->syntaxCopy();
    a->data[i] = e;^M
 }


Without it, optimize.c lines 86-87 will call indirectly this method, when some
(last) elemenets of exps is/are nulls, and segfault.

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