from Hacker News

Cosmopolitan Libc: your build-once run-anywhere C library

by moonlighter on 2/26/21, 5:44 PM with 11 comments

  • by dang on 2/26/21, 10:08 PM

    I understand the love these incredible projects are getting on HN right now, but this one was discussed a couple months ago:

    Cosmopolitan Libc: build-once run-anywhere C library - https://news.ycombinator.com/item?id=25556286 - Dec 2020 (166 comments)

    and the current related thread is still high on the front page—long may it reign:

    Show HN: Redbean – Single-file distributable web server - https://news.ycombinator.com/item?id=26271117 - Feb 2021 (182 comments)

    There are also these related threads:

    Actually Portable Executable - https://news.ycombinator.com/item?id=26273960 - Feb 2021 (133 comments)

    αcτµαlly pδrταblε εxεcµταblε - https://news.ycombinator.com/item?id=24256883 - Aug 2020 (286 comments)

    How Fat Does a Fat Binary Need to Be? - https://news.ycombinator.com/item?id=26103769 - Feb 2021 (68 comments)

    Others?

  • by guenthert on 2/26/21, 8:04 PM

    "That's a huge improvement in generated code size. The above two compiles used the same gcc flags"

    It would have been awfully nice to state the version of the compiler and the flags being used. With gcc 10 on Linux/AMD64, libc 4.15.0, I get with '-Os':

      --8<--
  strlcpy:
  .LFB5:
        .cfi_startproc
        pushq   %rbp
        .cfi_def_cfa_offset 16
        .cfi_offset 6, -16
        movq    %rdi, %rbp
        movq    %rsi, %rdi
        pushq   %rbx
        .cfi_def_cfa_offset 24
        .cfi_offset 3, -24
        movq    %rdx, %rbx
        subq    $24, %rsp
        .cfi_def_cfa_offset 48
        movq    %rsi, 8(%rsp)
        call    strlen
        testq   %rbx, %rbx
        movq    8(%rsp), %rsi
        je      .L1
        leaq    -1(%rbx), %rdx
        movq    %rbp, %rdi
        cmpq    %rax, %rdx
        cmova   %rax, %rdx
        movq    %rdx, %rcx
        movq    %rdx, %rcx
        rep movsb
        movb    $0, 0(%rbp,%rd  
  .L1ubq    $24, %rsp
        .cfi_def_cfa_offset 48
        movq    %rsi, 8(%rsp) 
        call    strlen
        testq   %rbx, %rbx
        movq    8(%rsp), %rsi
        je      .L1
        leaq    -1(%rbx), %rdx
        movq    %rbp, %rdi
        cmpq    %rax, %rdx
        cmova   %rax, %rdx
        movq    %rdx, %rcx
        cmova   %rax, %rdx
        movq    %rdx, %rcx
        addq    $24, %rsp
        .cfi_def_cfa_offset 24
        popq    %rbx
        .cfi_def_cfa_offset 16
        popq    %rbp
        .cfi_def_cfa_offset 8
        ret
        .cfi_endproc
  -->8--
    Which doesn't seem so bad.

  • by lostmsu on 2/26/21, 10:02 PM

    I missed an opportunity to ask in the previous thread: what would it take to link an app in a different language (say, Rust) with this library? Is it enough to just build an object file, that has libc functions assuming LP64 ABI as unresolved exports?

  • by musicale on 2/26/21, 8:37 PM

  • by gbrown_ on 2/26/21, 9:16 PM

  • by Gys on 2/26/21, 8:28 PM

    Run anywhere x86 ;-)

  • by d33lio on 2/26/21, 9:22 PM

    This seems incredibly ideal for writing malware / rats?