plotfi marked 2 inline comments as done.
plotfi added inline comments.

================
Comment at: clang/unittests/DirectoryWatcher/DirectoryWatcherTest.cpp:323
+          /*waitForInitialSync=*/false);
+  // llvm::Expected will throw an error if DW is an Error.
+  if (!DW)
----------------
gribozavr wrote:
> plotfi wrote:
> > gribozavr wrote:
> > > Call `llvm::cantFail` and there will be no need to explain anything.
> > I explained this in the other patch: 
> > 
> > cantFail is arguably worse. I want this test to tell me the cause of the 
> > crash (in this case, exceeding the inotify limit). What I want to happen is:
> > 
> > ```
> > Note: Google Test filter = DirectoryWatcherTest.AddFiles
> > [==========] Running 1 test from 1 test case.
> > [----------] Global test environment set-up.
> > [----------] 1 test from DirectoryWatcherTest
> > [ RUN      ] DirectoryWatcherTest.AddFiles
> > Expected<T> must be checked before access or destruction.
> > Unchecked Expected<T> contained error:
> > inotify_init1() error: out of inotify entries #0 0x0000000000246b8f 
> > llvm::sys::PrintStackTrace(llvm::raw_ostream&) 
> > /mnt/nvme0/llvm-project/llvm/lib/Support/Unix/Signals.inc:533:13
> >  #1 0x00000000002450d2 llvm::sys::RunSignalHandlers() 
> > /mnt/nvme0/llvm-project/llvm/lib/Support/Signals.cpp:69:18
> >  #2 0x0000000000247268 SignalHandler(int) 
> > /mnt/nvme0/llvm-project/llvm/lib/Support/Unix/Signals.inc:385:1
> >  #3 0x00007f17924eb890 __restore_rt 
> > (/lib/x86_64-linux-gnu/libpthread.so.0+0x12890)
> >  #4 0x00007f1790f94e97 gsignal /build/glibc-OTsEL5/glibc-
> > ...
> > ```
> > 
> > Wrapping the llvm::Expected in a cantFail hides this message, and instead 
> > you get the much less useful:
> > 
> > ```
> > Note: Google Test filter = DirectoryWatcherTest.AddFiles
> > [==========] Running 1 test from 1 test case.                               
> >                                                                             
> >                                                                             
> >          
> > [----------] Global test environment set-up.
> > [----------] 1 test from DirectoryWatcherTest
> > [ RUN      ] DirectoryWatcherTest.AddFiles
> > Failure value returned from cantFail wrapped call
> > UNREACHABLE executed at 
> > /mnt/nvme0/llvm-project/llvm/include/llvm/Support/Error.h:707!
> >  #0 0x0000000000246e0f llvm::sys::PrintStackTrace(llvm::raw_ostream&) 
> > /mnt/nvme0/llvm-project/llvm/lib/Support/Unix/Signals.inc:533:13
> >  #1 0x0000000000245352 llvm::sys::RunSignalHandlers() 
> > /mnt/nvme0/llvm-project/llvm/lib/Support/Signals.cpp:69:18
> >  #2 0x00000000002474e8 SignalHandler(int) 
> > /mnt/nvme0/llvm-project/llvm/lib/Support/Unix/Signals.inc:385:1
> >  #3 0x00007f20c64a8890 __restore_rt 
> > (/lib/x86_64-linux-gnu/libpthread.so.0+0x12890)
> >  #4 0x00007f20c4f51e97 gsignal 
> > /build/glibc-OTsEL5/glibc-2.27/signal/../sysdeps/unix/sysv/linux/raise.c:51:0
> >  #5 0x00007f20c4f53801 abort 
> > /build/glibc-OTsEL5/glibc-2.27/stdlib/abort.c:81:0
> >  #6 0x0000000000232b31 
> > (build/tools/clang/unittests/DirectoryWatcher/./DirectoryWatcherTests+0x232b31)
> > ```
> > 
> > I specifically _want_ llvm::Expected to propagate the error up.
> > I can drop the comments, because it should be fairly obvious here that DW 
> > is an llvm::Expected since I got rid of the autos.
> > 
> > To be clear, wrapping llvm::Expected in cantFail goes against the entire 
> > point of why I added this more robust error handling.
> > If someone's machine is failing on this test because they've exceeded their 
> > inotify limit, I would really like the message produced from 
> > strerror(errno) to bubble up to the top so that it is obvious to them that 
> > they need to either kill some tasks on their machine or up their inotify 
> > limit. 
> The automated checking in llvm::Expected is not guaranteed to happen (it is 
> behind LLVM_ENABLE_ABI_BREAKING_CHECKS). If you are not happy with the error 
> from `cantFail` I think everyone would appreciate an improvement there.
> 
> > I specifically _want_ llvm::Expected to propagate the error up.
> 
> I don't understand. It is not propagating anything up, it is just crashing in 
> the destructor.
Also, I have to point out here: cantFail is exactly the wrong tool here because 
this code can in fact fail if your system has exceeded its inotify limits. 


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D65829/new/

https://reviews.llvm.org/D65829



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