[all-commits] [llvm/llvm-project] f807d0: [lldb/test] Fix for flakiness in TestNSDictionaryS...

[Vedant Kumar via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: f807d0b4acdb70c5a15919f6e9b02d8b212d1088
      https://github.com/llvm/llvm-project/commit/f807d0b4acdb70c5a15919f6e9b02d8b212d1088
  Author: Vedant Kumar <vsk at apple.com>
  Date:   2020-05-11 (Mon, 11 May 2020)

  Changed paths:
    M lldb/test/API/lldbtest.py

  Log Message:
  -----------
  [lldb/test] Fix for flakiness in TestNSDictionarySynthetic

Summary:
TestNSDictionarySynthetic sets up an NSURL which does not initialize its
_baseURL member. When the test runs and we print out the NSURL, we print
out some garbage memory pointed-to by the _baseURL member, like:

```
_baseURL = 0x0800010020004029 @"d��qX"
```

and this can cause a python unicode decoding error like:

```
UnicodeDecodeError: 'utf8' codec can't decode byte 0xa0 in position
10309: invalid start byte
```

There's a discrepancy here because lldb's StringPrinter facility tries
to only print out "printable" sequences (see: isprint32()), whereas python
rejects the StringPrinter output as invalid utf8. For the specific error
seen above, lldb's `isprint32(0xa0) = true`, even though 0xa0 is not
really "printable" in the usual sense.

The problem is that lldb and python disagree on what exactly is
"printable". Both have dismayingly hand-rolled utf8 validation code
(c.f. _Py_DecodeUTF8Ex), and I can't really tell which one is more
correct.

I tried replacing lldb's isprint32() with a call to libc's iswprint():
this satisfied python, but broke emoji printing :|.

Now, I believe that lldb (and python too) ought to just call into some
battle-tested utf library, and that we shouldn't aim for compatibility
with python's strict unicode decoding mode until then.

FWIW I ran this test under an ASanified lldb hundreds of times but
didn't turn up any other issues.

rdar://62941711

Reviewers: JDevlieghere, jingham, shafik

Subscribers: lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D79645