[PATCH] D35735: [ubsan] Null-check pointers in -fsanitize=vptr (PR33881)

[Vedant Kumar via Phabricator via cfe-commits]

vsk created this revision.

The instrumentation generated by -fsanitize=vptr does not null check a
user pointer before loading from it. This causes crashes in the face of
UB member calls (this=nullptr), i.e it causes user programs to crash only
after UBSan is turned on.

The fix is to make run-time null checking a prerequisite for enabling
-fsanitize=vptr, and to then teach UBSan to reuse these run-time null
checks to make -fsanitize=vptr safe.

Testing: check-clang, check-ubsan, a stage2 ubsan-enabled build
(Test updates in compiler-rt to follow in a separate patch)

https://bugs.llvm.org/show_bug.cgi?id=33881
rdar://problem/32659008


https://reviews.llvm.org/D35735

Files:
  docs/UndefinedBehaviorSanitizer.rst
  include/clang/Basic/DiagnosticDriverKinds.td
  include/clang/Basic/DiagnosticGroups.td
  lib/CodeGen/CGExpr.cpp
  lib/Driver/SanitizerArgs.cpp
  test/CodeGenCXX/catch-undef-behavior.cpp
  test/CodeGenCXX/ubsan-devirtualized-calls.cpp
  test/CodeGenCXX/ubsan-type-checks.cpp
  test/CodeGenCXX/ubsan-vtable-checks.cpp
  test/Driver/fsanitize.c
  test/Driver/rtti-options.cpp

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