[clang] [-Wunsafe-buffer-usage] Emit a warning if pointer returned by vector::data and array::data is cast to larger type (PR #111910)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-m68k-linux-cross` running on `suse-gary-m68k-cross` while building `clang` at step 4 "build stage 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/27/builds/705

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 4 (build stage 1) failure: 'ninja' (failure)
...
[80/327] Building CXX object tools/clang/lib/Parse/CMakeFiles/obj.clangParse.dir/ParseCXXInlineMethods.cpp.o
In file included from /var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Parse/Parser.h:20,
                 from /var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/lib/Parse/ParseCXXInlineMethods.cpp:15:
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Sema/Sema.h:462:7: warning: ‘clang::Sema’ declared with greater visibility than the type of its field ‘clang::Sema::UnusedFileScopedDecls’ [-Wattributes]
  462 | class Sema final : public SemaBase {
      |       ^~~~
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Sema/Sema.h:462:7: warning: ‘clang::Sema’ declared with greater visibility than the type of its field ‘clang::Sema::TentativeDefinitions’ [-Wattributes]
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Sema/Sema.h:462:7: warning: ‘clang::Sema’ declared with greater visibility than the type of its field ‘clang::Sema::ExtVectorDecls’ [-Wattributes]
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Sema/Sema.h:462:7: warning: ‘clang::Sema’ declared with greater visibility than the type of its field ‘clang::Sema::DelegatingCtorDecls’ [-Wattributes]
[81/327] Building CXX object tools/clang/lib/Sema/CMakeFiles/obj.clangSema.dir/SemaExpr.cpp.o
FAILED: tools/clang/lib/Sema/CMakeFiles/obj.clangSema.dir/SemaExpr.cpp.o 
/usr/bin/c++ -DCLANG_EXPORTS -DGTEST_HAS_RTTI=0 -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/stage1/tools/clang/lib/Sema -I/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/lib/Sema -I/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include -I/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/stage1/tools/clang/include -I/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/stage1/include -I/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/llvm/include -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -fno-lifetime-dse -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -pedantic -Wno-long-long -Wimplicit-fallthrough -Wno-maybe-uninitialized -Wno-nonnull -Wno-class-memaccess -Wno-redundant-move -Wno-pessimizing-move -Wno-noexcept-type -Wdelete-non-virtual-dtor -Wsuggest-override -Wno-comment -Wno-misleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -fno-common -Woverloaded-virtual -fno-strict-aliasing -O3 -DNDEBUG -std=c++17  -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -MD -MT tools/clang/lib/Sema/CMakeFiles/obj.clangSema.dir/SemaExpr.cpp.o -MF tools/clang/lib/Sema/CMakeFiles/obj.clangSema.dir/SemaExpr.cpp.o.d -o tools/clang/lib/Sema/CMakeFiles/obj.clangSema.dir/SemaExpr.cpp.o -c /var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/lib/Sema/SemaExpr.cpp
In file included from /var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/lib/Sema/CheckExprLifetime.h:17,
                 from /var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/lib/Sema/SemaExpr.cpp:13:
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Sema/Sema.h:462:7: warning: ‘clang::Sema’ declared with greater visibility than the type of its field ‘clang::Sema::UnusedFileScopedDecls’ [-Wattributes]
  462 | class Sema final : public SemaBase {
      |       ^~~~
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Sema/Sema.h:462:7: warning: ‘clang::Sema’ declared with greater visibility than the type of its field ‘clang::Sema::TentativeDefinitions’ [-Wattributes]
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Sema/Sema.h:462:7: warning: ‘clang::Sema’ declared with greater visibility than the type of its field ‘clang::Sema::ExtVectorDecls’ [-Wattributes]
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Sema/Sema.h:462:7: warning: ‘clang::Sema’ declared with greater visibility than the type of its field ‘clang::Sema::DelegatingCtorDecls’ [-Wattributes]
c++: fatal error: Killed signal terminated program cc1plus
compilation terminated.
[82/327] Building CXX object tools/clang/lib/Sema/CMakeFiles/obj.clangSema.dir/SemaHLSL.cpp.o
In file included from /var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/lib/Sema/SemaHLSL.cpp:29:
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Sema/Sema.h:462:7: warning: ‘clang::Sema’ declared with greater visibility than the type of its field ‘clang::Sema::UnusedFileScopedDecls’ [-Wattributes]
  462 | class Sema final : public SemaBase {
      |       ^~~~
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Sema/Sema.h:462:7: warning: ‘clang::Sema’ declared with greater visibility than the type of its field ‘clang::Sema::TentativeDefinitions’ [-Wattributes]
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Sema/Sema.h:462:7: warning: ‘clang::Sema’ declared with greater visibility than the type of its field ‘clang::Sema::ExtVectorDecls’ [-Wattributes]
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Sema/Sema.h:462:7: warning: ‘clang::Sema’ declared with greater visibility than the type of its field ‘clang::Sema::DelegatingCtorDecls’ [-Wattributes]
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/lib/Sema/SemaHLSL.cpp: In function ‘llvm::dxil::ResourceClass getResourceClass(RegisterType)’:
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/lib/Sema/SemaHLSL.cpp:107:1: warning: control reaches end of non-void function [-Wreturn-type]
  107 | }
      | ^
[83/327] Building CXX object tools/clang/lib/Sema/CMakeFiles/obj.clangSema.dir/SemaFunctionEffects.cpp.o
In file included from /var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Sema/Lookup.h:27,
                 from /var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Sema/SemaInternal.h:18,
                 from /var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/lib/Sema/SemaFunctionEffects.cpp:19:
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Sema/Sema.h:462:7: warning: ‘clang::Sema’ declared with greater visibility than the type of its field ‘clang::Sema::UnusedFileScopedDecls’ [-Wattributes]
  462 | class Sema final : public SemaBase {
      |       ^~~~
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Sema/Sema.h:462:7: warning: ‘clang::Sema’ declared with greater visibility than the type of its field ‘clang::Sema::TentativeDefinitions’ [-Wattributes]
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Sema/Sema.h:462:7: warning: ‘clang::Sema’ declared with greater visibility than the type of its field ‘clang::Sema::ExtVectorDecls’ [-Wattributes]
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Sema/Sema.h:462:7: warning: ‘clang::Sema’ declared with greater visibility than the type of its field ‘clang::Sema::DelegatingCtorDecls’ [-Wattributes]
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/lib/Sema/SemaFunctionEffects.cpp: In member function ‘bool clang::Sema::FunctionEffectDiff::shouldDiagnoseConversion(clang::QualType, const clang::FunctionEffectsRef&, clang::QualType, const clang::FunctionEffectsRef&) const’:
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/lib/Sema/SemaFunctionEffects.cpp:1531:5: warning: this statement may fall through [-Wimplicit-fallthrough=]
 1531 |     switch (DiffKind) {
      |     ^~~~~~
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/lib/Sema/SemaFunctionEffects.cpp:1543:3: note: here

```

</details>

https://github.com/llvm/llvm-project/pull/111910