Skip to content

gh-124265: Remove redundant if statements in traceback.c #124272

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
wants to merge 2 commits into from
Closed

gh-124265: Remove redundant if statements in traceback.c #124272

Changes from 1 commit
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
c2f7861
Remove redundant if statements in traceback.c
rruuaanng Sep 20, 2024
43dab5c
Merge branch 'main' into 124265
skirpichev Sep 20, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
3 changes: 0 additions & 3 deletions Python/traceback.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -980,9 +980,6 @@ dump_traceback(int fd, PyThreadState *tstate, int write_header)
/* Trampoline frame */
frame = frame->previous;
}
if (frame == NULL) {
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Why, but why do you think that frame->previous on L981 is not NULL?

Copy link
Contributor Author

@rruuaanng rruuaanng Sep 20, 2024 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

If frame is part of a chain and there might be a situation where it’s traversed backwards, then at that point in the code

cpython/Python/traceback.c

Line 975 in 7a2d77c

frame = frame->previous;

It should break out. That’s what I think.
I’m not sure if my description is accurate. it’s just how I imagine the situation.

Copy link
Contributor Author

@rruuaanng rruuaanng Sep 20, 2024 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more. 

static void
dump_traceback(int fd, PyThreadState *tstate, int write_header)
{
    if (write_header) {
        PUTS(fd, "Stack (most recent call first):\n");
    }

    if (tstate_is_freed(tstate)) {
        PUTS(fd, "  <tstate is freed>\n");
        return;
    }

    _PyInterpreterFrame *frame = tstate->current_frame;
    if (frame == NULL) {
        PUTS(fd, "  <no Python frame>\n");
        return;
    }

    unsigned int depth = 0;
    while (1) {
        if (MAX_FRAME_DEPTH <= depth) {
            if (MAX_FRAME_DEPTH < depth) {
                PUTS(fd, "plus ");
                _Py_DumpDecimal(fd, depth);
                PUTS(fd, " frames\n");
            }
            break;
        }
        dump_frame(fd, frame);
        frame = frame->previous;
        if (frame == NULL) {
            break;
        }
        if (frame->owner == FRAME_OWNED_BY_CSTACK) {
            /* Trampoline frame */
            frame = frame->previous;
        }
        // if (frame == NULL) {
        //     break;
        // }
        /* Can't have more than one shim frame in a row */
        assert(frame->owner != FRAME_OWNED_BY_CSTACK);
        depth++;
    }
}

I hid the targets I needed to modify by commenting them out.

cpython/Python/traceback.c

Lines 983 to 985 in 7a2d77c

if (frame == NULL) {
break;
}

Then run PCbuild/build.bat, I then ran the tests using ./python Lib\test\test_traceback.py.
It seemed to run well as it passed all 347 tests in about 8.3 seconds.

PS E:\code\cc\cpython\alpha\cpython-main> ./python .\Lib\test\test_traceback.py
Running Debug|x64 interpreter...
...........................................................................................................................................................................................................................................................................................................................................................
----------------------------------------------------------------------
Ran 347 tests in 8.303s

OK

But I can't understand why it fails on CI. Maybe I ran the test incorrectly.

break;
}
/* Can't have more than one shim frame in a row */
assert(frame->owner != FRAME_OWNED_BY_CSTACK);
depth++;
Expand Down
Loading