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gerrit-public.fairphone.software / platform / system / libbase / 74f97276b38e7dfa8787654256894413696507bc
commit74f97276b38e7dfa8787654256894413696507bc[log] [tgz]
authorJiakai Zhang <jiakaiz@google.com>Mon Sep 25 16:21:30 2023 +0100
committerJiakai Zhang <jiakaiz@google.com>Mon Sep 25 19:40:53 2023 +0100
tree01c2ff62ff8a64d10ee803aef9e6c6116ca20eb1
parentae7f67463dccbf93c500c7e2176fa5843a4be7c3 [diff]
Use longer names for temporary vars in OR_RETURN/OR_FATAL.

Before this change, the macros declare a variable called `tmp`, which
may shadow a variable above that has the same name and cause a problem
when `expr` expends to something that contains `tmp`.

For example:

Result<int> tmp(1);
int a = OR_RETURN(std::move(tmp));
                            ^^^
          The `tmp` in the macro shadows it.

Without -Wall, this can lead to undefined behavior. Fortunately, the
Android build system uses -Wall so that it can catch this issue and
throw a compilation error, so undefined behavior will not happen.
However, it's still not great that the macros don't allow the operand to
expend to something that contains `tmp`.

This change mitigates the issue by using a longer name with a leading
"__" for the temporary variable.

Test: Presubmit
Change-Id: I5035570a21b6f0e1baf60a1d089a4b5eabd299f9
1 file changed
tree: 01c2ff62ff8a64d10ee803aef9e6c6116ca20eb1
  1. abi-dumps/
  2. include/
  3. tidy/
  4. .clang-format ⇨ ../../build/soong/scripts/system-clang-format-2
  5. abi_compatibility.cpp
  6. Android.bp
  7. chrono_utils.cpp
  8. chrono_utils_test.cpp
  9. cmsg.cpp
  10. cmsg_test.cpp
  11. CPPLINT.cfg
  12. endian_test.cpp
  13. errors_test.cpp
  14. errors_unix.cpp
  15. errors_windows.cpp
  16. expected_test.cpp
  17. file.cpp
  18. file_benchmark.cpp
  19. file_test.cpp
  20. format_benchmark.cpp
  21. function_ref_benchmark.cpp
  22. function_ref_test.cpp
  23. hex.cpp
  24. hex_test.cpp
  25. logging.cpp
  26. logging_splitters.h
  27. logging_splitters_test.cpp
  28. logging_test.cpp
  29. macros_test.cpp
  30. mapped_file.cpp
  31. mapped_file_test.cpp
  32. no_destructor_test.cpp
  33. NOTICE
  34. OWNERS
  35. parsebool.cpp
  36. parsebool_test.cpp
  37. parsedouble_test.cpp
  38. parseint_test.cpp
  39. parsenetaddress.cpp
  40. parsenetaddress_fuzzer.cpp
  41. parsenetaddress_fuzzer.dict
  42. parsenetaddress_test.cpp
  43. posix_strerror_r.cpp
  44. PREUPLOAD.cfg
  45. process.cpp
  46. process_test.cpp
  47. properties.cpp
  48. properties_test.cpp
  49. README.md
  50. result_test.cpp
  51. result_test_constraint.cpp
  52. scopeguard_test.cpp
  53. stringprintf.cpp
  54. stringprintf_test.cpp
  55. strings.cpp
  56. strings_test.cpp
  57. test_main.cpp
  58. TEST_MAPPING
  59. test_utils.cpp
  60. test_utils_test.cpp
  61. threads.cpp
  62. utf8.cpp
  63. utf8_test.cpp
README.md

libbase

Who is this library for?

This library is a collection of convenience functions to make common tasks easier and less error-prone.

In this context, "error-prone" covers both "hard to do correctly" and "hard to do with good performance", but as a general purpose library, libbase's primary focus is on making it easier to do things easily and correctly when a compromise has to be made between "simplest API" on the one hand and "fastest implementation" on the other. Though obviously the ideal is to have both.

Should my routine be added?

The intention is to cover the 80% use cases, not be all things to all users.

If you have a routine that's really useful in your project, congratulations. But that doesn't mean it should be here rather than just in your project.

The question for libbase is "should everyone be doing this?"/"does this make everyone's code cleaner/safer?". Historically we've considered the bar for inclusion to be "are there at least three unrelated projects that would be cleaned up by doing so".

If your routine is actually something from a future C++ standard (that isn't yet in libc++), or it's widely used in another library, that helps show that there's precedent. Being able to say "so-and-so has used this API for n years" is a good way to reduce concerns about API choices.

Any other restrictions?

Unlike most Android code, code in libbase has to build for Mac and Windows too.

Code here is also expected to have good test coverage.

By its nature, it's difficult to change libbase API. It's often best to start using your routine just in your project, and let it "graduate" after you're certain that the API is solid.