ggml : do not output unprintable characters on GGUF load failure

[CISC]

On failure to load a GGUF the first four characters of the file will be output to the console, leading to all kinds of trouble depending on the characters.

This is especially important to resolve before starting to support GGUF for other kinds of data files, see #9400 (review)

[JohannesGaessler]

It would maybe be nice to also add a test case to tests/test-gguf.cpp but I think this is a fairly minor issue.

[CISC]

It would maybe be nice to also add a test case to tests/test-gguf.cpp but I think this is a fairly minor issue.

Test for what though?

[CISC]

It would maybe be nice to also add a test case to tests/test-gguf.cpp but I think this is a fairly minor issue.

Test for what though?

Could capture stderr I guess?

[JohannesGaessler]

I don't know, would depend on what kind of issues you were able to provoke without the change. You could maybe assert that with unprintable characters in the gguf magic the string ???? is printed instead but I don't know how tedious that would be to implement vs. the gain in test coverage.

[CISC]

I tried, but since GGML_LOG writes to stderr by default it got too messy (would require a logging callback or freopen), I don't think it's worth it.

[JohannesGaessler]

That's fine, as long as it's not possible to provoke major issues such as a crash it's not that important anyways.

[CISC]

That's fine, as long as it's not possible to provoke major issues such as a crash it's not that important anyways.

No, at worst it will mess up your terminal on the right character sequence.