[all-commits] [llvm/llvm-project] e3f16d: [unittest][Support] Fix bad negation of signed int...

[Duo Wang via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: e3f16de9a33d48f6a9d8035a9aebfdb0e3a16ea5
      https://github.com/llvm/llvm-project/commit/e3f16de9a33d48f6a9d8035a9aebfdb0e3a16ea5
  Author: Duo Wang <duow1 at uci.edu>
  Date:   2023-11-27 (Mon, 27 Nov 2023)

  Changed paths:
    M llvm/unittests/Support/LEB128Test.cpp

  Log Message:
  -----------
  [unittest][Support] Fix bad negation of signed integer in LEB128Test.SLEB128Size (#72700)

I came across an undefined behavior when running Support unit tests with
UBSAN on Windows.
```bash
[ RUN      ] LEB128Test.SLEB128Size
C:\llvm\unittests\Support\LEB128Test.cpp:382:3: runtime error: negation of -9223372036854775808 cannot be represented in type 'long long'; cast to an unsigned type to negate this value to itself
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior C:\llvm\unittests\Support\LEB128Test.cpp:382:3 in 
```

UBSAN did not report the same error on macOS, but the negation still
seemed invalid (`0x8000000000000000LL == -0x8000000000000000LL`
evaluated to `true`).
I can confirm that `-0x7fffffffffffffffLL - 1` results in the expected
value on both platforms.