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Name: Gary Benson
Member since: 2001-05-31 00:39:54
Last Login: 2012-10-24 12:18:42

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Infinity status

I’m winding down for a month away from Infinity. The current status is that the language and note format changes for 0.0.2 are all done. You can get them with:

git clone

There’s also the beginnings of an Emacs major mode for i8 in there too. My glibc tree now has notes for td_ta_thr_iter as well as td_ta_map_lwp2thr. That’s two of the three hard ones done. Get them with:

git clone -b infinity2

FWIW td_thr_get_info is just legwork and td_thr_tls_get_addr is just a wrapper for td_thr_tlsbase; td_thr_tlsbase is the other hard note.

All notes have testcases with 100% bytecode coverage. I may add a flag for I8X to make not having 100% coverage a failure, and make glibc use it so nobody can commit notes with untested code.

The total note size so far is 720 bytes so I may still manage to get all five libpthread notes implemented in less than 1k:

Displaying notes found at file offset 0x00018f54 with length 0x000002d0:
  Owner                 Data size	Description
  GNU                  0x00000063	NT_GNU_INFINITY (inspection function)
    Signature: libpthread::__lookup_th_unique(i)ip
  GNU                  0x00000088	NT_GNU_INFINITY (inspection function)
    Signature: libpthread::map_lwp2thr(i)ip
  GNU                  0x000000cd	NT_GNU_INFINITY (inspection function)
    Signature: libpthread::__iterate_thread_list(Fi(po)oipii)ii
  GNU                  0x000000d2	NT_GNU_INFINITY (inspection function)
    Signature: libpthread::thr_iter(Fi(po)oiipi)i

Syndicated 2015-11-25 10:33:07 from

Infinity updates

In case you hadn’t noticed, I8C 0.0.1 was released last week. As well as the note compiler, this package contains I8X, an interpreter for unit testing compiled notes.

In case you had noticed and you’ve been working with it, please note there’s some compatibility-breaking source language and note format changes in the pipeline.

Infinity has a mailing list, and I want you to subscribe to it. Infinity isn’t just my project–anybody who might either produce or consume Infinity notes has a stake in this:

  • If you’re working on a debugger or other tool that might consume Infinity notes then you have a stake.
  • If you’re working on a library that might expose some API via Infinity notes then you have a stake.

I don’t know every issue that Infinity will have to solve, and you know things I need to know. So don’t sit on the sidelines! Send an empty message to and get involved.

Syndicated 2015-10-28 10:41:47 from

Infinity compiler update

I had hoped to make a first release of i8c today but I still have one open issue so you’ll have to wait until next week. Until then here is some note source for you to ponder:

define test::factorial returns int
    argument int x
    extern func int (int) factorial

    load 1
    bne not_done_yet

    load 1

As hints I will a) point you at section 2.5 of the DWARF spec, and b) mention that argument and extern directives instruct the caller and runtime respectively to push entries onto the stack.

Your homework is to see how much of the language and runtime you can infer from this one function.

You may ask questions.

Syndicated 2015-10-02 16:27:05 from

Infinity compiler

When I said I’d never written a compiler, that’s actually a lie: I did some work on the Ceylon compiler a few years back. It wasn’t a very enriching experience but at least I know what ASTs and visitors are.

Anyway, the C-like syntax I talked about Friday might have been a little optimistic. I wanted the source to not be full of stack-shuffling but that’s not going to happen. Partly because I’d been assuming that the problem of compiling to a stack-based instruction set was solved: I was thinking of Java, but of course Java has local variables so it’s not exactly a stack-based instruction set, it’s stack and 65,536 registers–kind of the opposite problem! I didn’t find much online about compiling to stack-based instruction sets other than “it’s hard”.

I could probably manage something, but given that the total output of the compiler for glibc will likely be a hundred or so bytes of instructions, it doesn’t make sense to spend a huge amount of time on it.

The Infinity function compiler is therefore going to be something of a helpful assembler.

Syndicated 2015-09-15 09:59:36 from

Infinity function compiler

Yesterday I reworked the note format to allow functions as first-class objects, and then I had an idea about how to implement the note compiler.

I’d already thought I could have the compiler emit assembly to avoid having to think about endianness, but I couldn’t figure out how to do other platform-specific stuff like 32- vs 64-bit, or choosing which of the three LWP ID to thread descriptor mapping styles to use. My idea was to not only output to the assembler but to input from the C preprocessor as well. That way I can do all the conditional stuff in there, driven by glibc’s include files and CPPFLAGS.

Yeah, I think I can write a compiler that knows nothing about the platform it’s compiling for.

So, I spent all morning messing around with glibc’s build system. I’ve come up with this:

  1. Each machine’s tls.h will have some Infinity definitions following the ones for libthread_db. Here’s the one for x86_64:
    /* Magic for libthread_db to know how to do THREAD_SELF.  */
    #define DB_THREAD_SELF_INCLUDE  /* For the FS constant.  */
    /* Magic for Infinity to know how to do THREAD_SELF.  */
    #define I8_TS_CTA_VALUE FS

    I could probably generate the libthread_db ones from the Infinity ones… but… later.

  2. glibc has a script to generate assembler include files, to get constants and offsets from C headers into the assembler. I wrote a tls-infinity.sym file that the build system turns into tls-infinity.h for me.
  3. The source for map_lwp2thr is infinity_map_lwp2thr.i8. That includes tls-infinity.h and, on x86_64, conditionally includes infinity_lookup_th_unique_cta.i8 to perform the mapping in the correct way for that platform.
  4. infinity_map_lwp2thr.i8 gets fed into the C preprocessor which a) does all the conditionality and b) expands all the constants (as a total bonus!)

This leaves me with this lovely file to write a compiler for.

I’ve never written a compiler.

Syndicated 2015-09-11 13:56:04 from

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