[Lldb-commits] [lldb] [lldb][Windows] Don't synthesise a fake thread name from the executable (PR #199983)

[Charles Zablit via lldb-commits]

charles-zablit wrote:

I experimented with this program:

```cpp
#include <windows.h>
#include <processthreadsapi.h>
#include <stdio.h>

int main() {
    HANDLE thread = GetCurrentThread();

    HRESULT hr = SetThreadDescription(thread, L"MyAwesomeThread");
    if (FAILED(hr)) {
        fprintf(stderr, "SetThreadDescription failed: 0x%08lx\n", hr);
        return 1;
    }

    printf("Thread name set successfully.\n"); // break here
    return 0;
}
```

# With `LLDB_USE_LLDB_SERVER=0`
```
lldb.exe "C:\Users\charleszablit\Developer\testing\main.exe" -o "break set -p 'break here'" -o r -o q     
(lldb) target create "C:\\Users\\charleszablit\\Developer\\testing\\main.exe"
Current executable set to 'C:\Users\charleszablit\Developer\testing\main.exe' (x86_64).
(lldb) break set -p 'break here'
Breakpoint 1: where = main.exe`main + 81 at main.cpp:14, address = 0x00000001400072d1
(lldb) r
Process 9400 launched: 'C:\Users\charleszablit\Developer\testing\main.exe' (x86_64)
Process 9400 stopped
* thread #1, name = 'MyAwesomeThread', stop reason = breakpoint 1.1
       frame #0: 0x00007ff7141272d1 main.exe`main at main.cpp:14
   11           return 1;
   12       }
   13  
-> 14       printf("Thread name set successfully.\n"); // break here
   15       return 0;
   16   }
(lldb) q
```

# With `LLDB_USE_LLDB_SERVER=1` (and the fix):

```
lldb.exe "C:\Users\charleszablit\Developer\testing\main.exe" -o "break set -p 'break here'" -o r -o q
(lldb) target create "C:\\Users\\charleszablit\\Developer\\testing\\main.exe"
Current executable set to 'C:\Users\charleszablit\Developer\testing\main.exe' (x86_64).
(lldb) break set -p 'break here'
Breakpoint 1: where = main.exe`main + 81 at main.cpp:14, address = 0x00000001400072d1
(lldb) r
ValueError: compile(): unrecognised flags
Process 40364 launched: 'C:\Users\charleszablit\Developer\testing\main.exe' (x86_64)
Process 40364 stopped
* thread #1, stop reason = breakpoint 1.1
       frame #0: 0x00007ff7141272d1 main.exe`main at main.cpp:14
   11           return 1;
   12       }
   13  
-> 14       printf("Thread name set successfully.\n"); // break here
   15       return 0;
   16   }
(lldb) q
```

So this is still a regression compared to the current default behavior without `LLDB_USE_LLDB_SERVER=1`. I will look into making both paths behave the same.

https://github.com/llvm/llvm-project/pull/199983