Re: How does nativecomp compile circular lists?

[Jimmy Yuen Ho Wong <wyuenho@gmail.com>]

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I think I've found out what that stacktrace means. The regular expression
in disassemble-internal hasn't taken into account LLVM's objdump output
format for mach-o objects. The first couple of lines of the *Disassemble*
buffer looks like this on macOS:


/Users/wyuenho/.emacs.d/eln-cache/28_0_50-83d1a9b9/markdown-mode-4888e153-14d4f01e.eln:
file format mach-o 64-bit x86-64


Disassembly of section __TEXT,__text:

0000000000002fa0 <_maybe_gc_quit>:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/objdump:
warning:
'/Users/wyuenho/.emacs.d/eln-cache/28_0_50-83d1a9b9/markdown-mode-4888e153-14d4f01e.eln':
failed to parse debug information for
/Users/wyuenho/.emacs.d/eln-cache/28_0_50-83d1a9b9/markdown-mode-4888e153-14d4f01e.eln
    2fa0: 8b 05 86 9f 08 00             movl 565126(%rip), %eax  # 8cf2c
<_quitcounter>
    2fa6: 83 c0 01                     addl $1, %eax

Jimmy


On Tue, Jul 27, 2021 at 10:28 AM Andrea Corallo <akrl@sdf.org> wrote:

> Jimmy Yuen Ho Wong <wyuenho@gmail.com> writes:
>
> > I'm not exactly sure how to even ask this question, as I've seen various
> packages fail to natively compile circular lists
> > or optimize it wrongly. So I've come up with a simple test case for me
> to be able to disassemble the bytecode and the
> > native code, and see if I could spot the problem, but disassembling
> natively compiled code doesn't seem to work.
> >
> > Test case:
> >
> > (defun test-circular-list ()
> >   (let ((l (list 1 2 3)))
> >     (setcdr (last l) l)
> >     l))
> >
> > (print (test-circular-list))
> >
> > (provide 'test-circular-list)
> >
> > M-x emacs-lisp-byte-compile-and-load
> > M-x disassemble RET test-circular-list (works)
> >
> > M-x emacs-lisp-native-compile-and-load
> > M-x disassemble RET test-circular-list (doesn't work)
> >
> > Debugger entered--Lisp error: (search-failed
> "^.*<F746573742d63697263756c61722d6c697374_test_cir...")
> >
>  re-search-forward("^.*<F746573742d63697263756c61722d6c697374_test_cir...")
> >   disassemble-internal(test-circular-list 0 nil)
> >   disassemble(test-circular-list nil 0 t)
> >   funcall-interactively(disassemble test-circular-list nil 0 t)
> >   command-execute(disassemble record)
> >   execute-extended-command(nil "disassemble" nil)
> >   funcall-interactively(execute-extended-command nil "disassemble" nil)
> >   command-execute(execute-extended-command)
> >
> > Furthermore, this test case, though superficially similar, doesn't seem
> to be able to reproduce the same failure to
> > natively compile issue as seen in powerline.
> >
> > There seems to be more than one thing wrong with this journey into my
> deep dive into how native compiling circular lists
> > work.
> >
> > Jimmy Yuen Ho Wong
> >
>
> Hi Jimmy,
>
> I'm failing to reproduce this issue.
>
> Disassembling following your instructions works here. Also the compiled
> `test-circular-list' function as expected here.
>
> Am I missing something?
>
> Best Regards
>
>   Andrea
>

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