exception handling

Author: rcj1

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/Signature/Signature_1.cs

@@ -54,8 +54,6 @@ TypeHandle ISignature.DecodeFieldSignature(BlobHandle blobHandle, ModuleHandle m
 
     TargetPointer ISignature.GetVarArgArgsBase(TargetPointer vaSigCookieAddr)
     {
-        if (vaSigCookieAddr == TargetPointer.Null)
-            throw new ArgumentException("VASigCookie address must be non-null.", nameof(vaSigCookieAddr));
         // Compute the address of the first argument. On x86 the args are pushed below the cookie
         // pointer (stack grows down on the args walk), so the first argument lies at
         //   vaSigCookieAddr + sizeOfArgs.
@@ -73,8 +71,6 @@ TargetPointer ISignature.GetVarArgArgsBase(TargetPointer vaSigCookieAddr)
 
     void ISignature.GetVarArgSignature(TargetPointer vaSigCookieAddr, out TargetPointer signatureAddress, out uint signatureLength)
     {
-        if (vaSigCookieAddr == TargetPointer.Null)
-            throw new ArgumentException("VASigCookie address must be non-null.", nameof(vaSigCookieAddr));
         Data.VASigCookie cookie = GetCookie(vaSigCookieAddr);
 
         signatureAddress = cookie.SignaturePointer;
@@ -85,9 +81,6 @@ void ISignature.GetVarArgSignature(TargetPointer vaSigCookieAddr, out TargetPoin
     private Data.VASigCookie GetCookie(TargetPointer vaSigCookieAddr)
     {
         TargetPointer vaSigCookie = _target.ReadPointer(vaSigCookieAddr);
-        if (vaSigCookie == TargetPointer.Null)
-            throw new InvalidOperationException("VASigCookie pointer is null.");
-
         return _target.ProcessedData.GetOrAdd<Data.VASigCookie>(vaSigCookie);
     }
 }

src/native/managed/cdac/tests/SignatureTests.cs

@@ -140,7 +140,7 @@ public void GetVarArgSignature_NullCookiePointer_Throws(MockTarget.Architecture
             out ulong vaSigCookieAddr, out _, nullCookie: true);
         ISignature signature = target.Contracts.Signature;
 
-        Assert.Throws<InvalidOperationException>(() => signature.GetVarArgSignature(new TargetPointer(vaSigCookieAddr), out _, out _));
+        Assert.Throws<VirtualReadException>(() => signature.GetVarArgSignature(new TargetPointer(vaSigCookieAddr), out _, out _));
     }
 
     [Theory]
@@ -151,7 +151,7 @@ public void GetVarArgArgsBase_NullCookiePointer_Throws(MockTarget.Architecture a
             out ulong vaSigCookieAddr, out _, nullCookie: true);
         ISignature signature = target.Contracts.Signature;
 
-        Assert.Throws<InvalidOperationException>(() => signature.GetVarArgArgsBase(new TargetPointer(vaSigCookieAddr)));
+        Assert.Throws<VirtualReadException>(() => signature.GetVarArgArgsBase(new TargetPointer(vaSigCookieAddr)));
     }
 
     [Theory]