x86-64-ABI Alternatives

x86-64-ABI reviews and mentions

• Addressing the adding situation – Matt Godbolt
  4 projects | news.ycombinator.com | 2 Dec 2025
• We found a bug in Go's ARM64 compiler
  7 projects | news.ycombinator.com | 8 Oct 2025

  Ehh I wouldn’t say so (thanks for the correct link for ARM64 though in any case). What you need to be comparing to here is DWARF[1,2] section 6.4, and while it’s not as bad as other parts of DWARF, I still think it’s plenty complicated.

  [1] https://dwarfstd.org/doc/DWARF5.pdf#page=171

  [2] Slightly modified by psABI[3] section 3.7 for x86-64 or the LSB[4] section 11.6 for ARM64, but at this point that’s a drop in the bucket as far as overall complexity is concerned.

  [3] https://gitlab.com/x86-psABIs/x86-64-ABI/-/jobs/artifacts/ma...

  [4] https://refspecs.linuxfoundation.org/LSB_4.0.0/LSB-Core-gene...

• The repercussions of a typo in C++ & Rust
  1 project | news.ycombinator.com | 6 Sep 2025

  > if an argument fits into the size of a register, it's better to pass by value to avoid the extra indirection.

  Whether an argument is passed in a register or not is unfortunately much more nuanced than this: it depends on the ABI calling conventions (which vary depending on OS as well as CPU architecture). There are some examples where the argument will not be passed in a register despite being "small enough", and some examples where the argument may be split across two or more registers.

  For instance, in the x86-64 ELF ABI spec [0], the type needs to be <= 16 bytes (despite registers only being 8 bytes), and it must not have any nontrivial copy / move constructors. And, of course, only some registers are used in this way, and if those are used up, your value params will be passed on the stack regardless.

  [0] Section 3.2.3 of https://gitlab.com/x86-psABIs/x86-64-ABI

• Evolution of the ELF object file format
  2 projects | news.ycombinator.com | 27 May 2024
• Linux/ELF .eh_frame from the bottom up
  2 projects | news.ycombinator.com | 16 Feb 2024

  Linux uses the sysv calling convention. I believe these are the official or semi-official documents for x86 64-bit and 32-bit, respectively:

  https://gitlab.com/x86-psABIs/x86-64-ABI (Table 3.4 in section 3.2.3 lists which registers may be clobbered and which must be saved)

• Book recommendations.
  1 project | /r/asm | 5 Dec 2023

  System V Application Binary Interface AMD64 Architecture Processor Supplement

• Six Great Features with the Upcoming Linux 6.6 Kernel
  1 project | news.ycombinator.com | 29 Oct 2023

  ABI is just the name for any stable binary interface between parts of a program, eg in C there is a well-defined ABI for calling functions: https://gitlab.com/x86-psABIs/x86-64-ABI/-/jobs/artifacts/ma... https://www.agner.org/optimize/calling_conventions.pdf

  If you combine that with a stable set of C function names and parameters, then you could define an ABI for kernel modules if you (and the Linux developers) wanted. While it sounds like a good idea, the outcome probably wouldn't be great for users.

• Does C++ have a stable ABI or not?
  1 project | /r/cpp | 29 Apr 2023

  But in the same breath, that paragraph's footnote points directly to the Itanium C++ ABI specification which seems to do precisely what they said has never been done. (I've filed a bug...).

• What x64 ABI does linux / GCC ACTUALLY use?
  1 project | /r/linux | 4 Feb 2023

  The supposed latest psABI specs (https://gitlab.com/x86-psABIs/x86-64-ABI) contain the following, with regards to classifying aggregates for argument passing (section 3.2.3, page 24, of the AMD64 ABI 1.0 – December 6, 2022 specs):

• Change default CPU type?
  1 project | /r/Proxmox | 20 Dec 2022

  RHEL, from version 9, requires x86-64 v2. The levels are a common effort between several companies, AMD included. The definitions can be found in this repo, and here is the latest PDF.

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