[ASan/Win] Fix failing test after ce44fe199bbf

[chrish_ericsson_atx]

Summary

Test includes array access with computed index of -3,
which is unreasonable. New diagnostic warning introduced
by commit ce44fe199bbf catches this at compile time.
Since this test is compiled with -Werror, the new diagnostic
causes a build failure for this test. Fixed by inserting
pragmas to ignore the warning. Perhaps there is a more
sensible way for this test to be constructed such that the
index won't be utter nonsense, but as I'm not familiar with
the intent of this test, it seemed safe to just dodge the
diagnostic for the one line of code that triggers it.

[chrish_ericsson_atx]

Note -- I do not have appropriate resources configured to test this patch. If this patch fails pre-commit tests, I'd be grateful if someone who is already set up for Windows-based development could make any corrections needed here.

[rnk]

IMO it would be more resiliant to hide the index or the pointer from the compiler, let me try to put together that fix.

[rnk]

I fixed it and it went green, thanks for the fix and the heads up though:
https://lab.llvm.org/buildbot/#/builders/127/builds/12308

[chrish_ericsson_atx]

Abandoning change, as @mk addressed this by hiding the index expression from the compiler (commit rGb9af157fd18d).

compiler-rt/test/asan/TestCases/Windows/dll_operator_array_new_with_dtor_left_oob.cpp

 // RUN: %clang_cl_asan -Od %p/dll_host.cpp -Fe%t
 // RUN: %clang_cl_asan -LD -Od %s -Fe%t.dll
 // RUN: not %run %t %t.dll 2>&1 | FileCheck %s
 
 struct C {
   int x;
   ~C() {}
 };
 
 extern "C" __declspec(dllexport)
 int test_function() {
   C *buffer = new C[42];
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Warray-bounds"
   buffer[-(1 + sizeof(void*) / 4)].x = 42;
+#pragma clang diagnostic pop
   // CHECK: AddressSanitizer: heap-buffer-overflow on address [[ADDR:0x[0-9a-f]+]]
   // CHECK: WRITE of size 4 at [[ADDR]] thread T0
   // CHECK-NEXT: test_function {{.*}}dll_operator_array_new_with_dtor_left_oob.cpp:[[@LINE-3]]
   // CHECK-NEXT: main {{.*}}dll_host.cpp
   //
   // FIXME: Currently it says "4 bytes ... left of 172-byte region",
   //        should be "8 bytes ... left of 168-byte region", see
   //        https://code.google.com/p/address-sanitizer/issues/detail?id=314
   // CHECK: [[ADDR]] is located {{.*}} bytes to the left of {{(172|176)}}-byte region
   // FIXME: Should get rid of the malloc/free frames called from the inside of
   // operator new/delete in DLLs when using -MT CRT.
   // FIXME: The operator new frame should have [].
   // CHECK-LABEL: allocated by thread T0 here:
   // CHECK:        operator new
   // CHECK-NEXT:   test_function {{.*}}dll_operator_array_new_with_dtor_left_oob.cpp:[[@LINE-16]]
   // CHECK-NEXT:   main {{.*}}dll_host.cpp
   // CHECK-LABEL: SUMMARY
   delete [] buffer;
   return 0;
 }