Segmentation fault for `Font(fontbuffer=object())`

[user202729]

Please provide all mandatory information!

Describe the bug (mandatory)

fitz.Font(fontbuffer=object()) causes a segmentation fault.

To Reproduce (mandatory)

See above.

Expected behavior (optional)

It should raise a TypeError or something.

Your configuration (mandatory)

Python 3.9.1, wheel.

Additional context (optional)

This is not how the library is supposed to be used, but mistakes can happen (for example pass a fontTools.TTFont object in), and segmentation faults are annoying in Python (normally it would print a traceback and let the user catch it)

To generalize, perhaps there should be some way to make the functions that take AnyType arguments safe from user errors?

[user202729]

Looks like that normally there's a check, but in this case it's missing.

The straight forward fix would be

--- a/fitz/helper-stext.i
+++ b/fitz/helper-stext.i
@@ -830,6 +830,7 @@ fz_font *JM_get_font(fz_context *ctx,
         // fontbuffer
         have_buffer:;
         res = JM_BufferFromBytes(ctx, fontbuffer);
+        if (!res) THROWMSG(gctx, "bad type: 'fontbuffer'");
         font = fz_new_font_from_buffer(ctx, NULL, res, index, 0);
         goto fertig;

but in this case it raises a warning (also is there a memory leak?)

---

Searching a bit in the source code, there are some other instances that the result is not checked against null value. (twice in Document.insertImage, once in Tools.insert_contents)

[JorjMcKie]

Thanks for spotting this.
Yes, this case is a left-over from the time when the Font class was introduced.
I have already corrected it in my local version.

[JorjMcKie]

I usually use a macro EXISTS, which checks for NULL and Python-True.

[malizheng]

I also encountered a similar error. When encountering this "Segmentation fault: 11" exception, "try: except:" cannot recognize this exception, and the program will exit abnormally. Is there any other way to identify this kind of exception in python?

[JorjMcKie]

Is there any other way to identify this kind of exception in python?

No - and that exactly is the problem - the Python interpreter itself is brought down.
For every such incident, please submit an issue and material to reproduce the error.
I am able to test stuff under Windows and Linux (only) - not MAC OSX.

[user202729]

There's faulthandler to print a traceback on segmentation fault -- nevertheless, it's never possible to catch the error.

Also, since this error is not fixed (in the newest version on GitHub/pypi), it might be the same (or related) error.

Searching a bit in the source code, there are some other instances that the result is not checked against null value. (twice in Document.insertImage, once in Tools.insert_contents)

[JorjMcKie]

Fixed by v1.18.7, currently being uploaded.