[PATCH] D76252: [lld-macho] Add basic support for linking against dylibs

[Rui Ueyama via Phabricator via llvm-commits]

ruiu added a comment.

In D76252#1928398 <https://reviews.llvm.org/D76252#1928398>, @jhenderson wrote:

> In D76252#1926005 <https://reviews.llvm.org/D76252#1926005>, @ruiu wrote:
>
> > As to the tests, we generally don't use yaml2obj to write tests (except for COFF which is historically using yaml2obj). If you are using yaml2obj just until lld itself is able to produce files used by tests, I don't think you have to spend too much time writing tests in yaml2obj. Instead, you can submit binary files for now and then replace them later.
>
>
> Hi @ruiu,
>
> I'm just doing a quick drive by comment here, since I'm not really doing much LLD work at the moment myself. Why are you opposed to yaml2obj being used to generate test inputs instead of llvm-mc? Surely yaml2obj gives more direct control over what is actually in the input? In llvm-mc you only have relatively limited control over some things like relocations.
>
> It seems to me like yaml2obj is a better instrument to be using for the vast majority of test cases, with only a limited set using llvm-mc as a catch-all test to make sure that we don't miss some odd interaction. Of course, this is all making the assumption that mach-o yaml2obj is straightforward to use (I have a feeling it might not be).


You can write tests with yaml2obj too, but if you take a look at ELF, don't you think that we can write fine-grained test cases with llvm-mc too? I want tests to be realistic input files, and in that respect, test cases written in llvm-mc are better than ones in obj2yaml.

I also found that tests written in llvm-mc are easier to maintain. For example, imagine that you already have a test file containing tests for relocations and you want to add a new type of relocation. Then, you'll have to not only add a new relocation to a yaml file but also add a few extra bytes with some addend at a right bit-wise position to the .text section, which isn't easy to do by hand. So, I guess you'll end up writing a test in assembly, compile it and then convert it to yaml -- but if that's the case, we should write tests in assembly in the first place. On the other hand, I didn't find a test case that is easy to write in yaml but not in assembly. There might be some, but that shouldn't be too many. So it looks to me that llvm-mc is a better choice to write test files.


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