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Re:AsmBB – a lightweight web forum engine written in assembl... by pengaru on Saturday January 13, 2024 @04:09PM (#38984596)
C is generally first compiled into assembly anyways.

When you program in assembly you're basically just doing the job of the compiler, and can call all the same library functions C code can. You just have to follow the calling conventions of the architecture. It's cumbersome and tedious, but nowhere near impossible.

x64 made calling functions more annoying by using registers then spilling over into the stack after exhausting those. x32 was more pleasant by far, since it only used the stack. x64's convention produces faster code though, by keeping stuff in registers.

Re:AsmBB – a lightweight web forum engine written in assembl... by nineteen999 on Saturday January 13, 2024 @05:33PM (#38985319)
> x32 was more pleasant by far, since it only used the stack

Maybe I misunderstand you, but this is completely dependent on compiler, operating system etc, there are multiple calling conventions for x86-32, eg. cdecl, fastcall ...

https://en.wikipedia.org/wiki/X86_calling_conventions

Re:AsmBB – a lightweight web forum engine written in assembl... by pengaru on Saturday January 13, 2024 @07:20PM (#38986121)
Apologies, my experience is SysV-centric for amd64, as described here[0] under the Parameter Passing section, which is a clustrfuck compared to the simplicity of the 386 SysV ABI as described here[1]:

  > Argument words are pushed onto the stack in reverse order (that is, the
  > rightmost argument in C call syntax has the highest address), preserving the
  > stack’s word alignment. All incoming arguments appear on the stack, resid-
  > ing in the stack frame of the caller.
Both links were found @ https://wiki.osdev.org/System_V_ABI

[0] https://www.uclibc.org/docs/psABI-x86_64.pdf

[1] https://www.sco.com/developers/devspecs/abi386-4.pdf

Re:AsmBB – a lightweight web forum engine written in assembl... by kristianp on Saturday January 13, 2024 @05:37PM (#38985352)
> C is generally first compiled into assembly anyways.

I don't think that's right. C is compiled into an intermediate representation first. It's true that you can ask GCC etc. to generate assembly output, but it's not the default.

Re:AsmBB – a lightweight web forum engine written in assembl... by pengaru on Saturday January 13, 2024 @07:08PM (#38986066)
> I don't think that's right. C is compiled into an intermediate representation first. It's true that you can ask GCC etc. to generate assembly output, but it's not the default.

Just because there's an IR within the compiler doesn't mean there's no "assembly" stage. What do you think the "-pipe" flag to gcc is for? It pipes the compiler output into the assembler, rather than using a temporary .s file.

gcc has four main stages going from source to executable: preprocessor->compiler->assembler->linker.

Edit, for your convenience, gcc -save-temps example:

  > [user@host /tmp/foo]$ ls
  > f.c
  > [user@host /tmp/foo]$ cat f.c
  > #include <stdio.h>
  >
  > int main(int argc, char **argv)
  > {
  >         puts("Hello world!");
  >
  >         return 0;
  > }
  > [user@host /tmp/foo]$ gcc -o f -save-temps f.c
  > [user@host /tmp/foo]$ ls -l
  > total 48
  > -rwxr-xr-x 1 user user 15416 Jan 13 16:50 f
  > -rw-r--r-- 1 user user    91 Jan 13 16:49 f.c 
  > -rw-r--r-- 1 user user 17145 Jan 13 16:50 f.i 
  > -rw-r--r-- 1 user user  1496 Jan 13 16:50 f.o 
  > -rw-r--r-- 1 user user   515 Jan 13 16:50 f.s 
  > [user@host /tmp/foo]$ cat f.s
  >         .file   "f.c"
  >         .text
  >         .section        .rodata
  > .LC0:
  >         .string "Hello world!"
  >         .text
  >         .globl  main
  >         .type   main, @function
  > main:
  > .LFB0:
  >         .cfi_startproc
  >         pushq   %rbp
  >         .cfi_def_cfa_offset 16
  >         .cfi_offset 6, -16
  >         movq    %rsp, %rbp
  >         .cfi_def_cfa_register 6
  >         subq    $16, %rsp
  >         movl    %edi, -4(%rbp)
  >         movq    %rsi, -16(%rbp)
  >         leaq    .LC0(%rip), %rax
  >         movq    %rax, %rdi
  >         call    puts@PLT
  >         movl    $0, %eax
  >         leave
  >         .cfi_def_cfa 7, 8
  >         ret
  >         .cfi_endproc
  > .LFE0:
  >         .size   main, .-main
  >         .ident  "GCC: (GNU) 13.1.1 20230429"
  >         .section        .note.GNU-stack,"",@progbits
  > [user@host /tmp/foo]$ ./f
  > Hello world!
  > [user@host /tmp/foo]$ 
  >
Re:AsmBB – a lightweight web forum engine written in assembl... by kristianp on Sunday January 14, 2024 @04:41PM (#38994707)
Thanks for the correction, I assumed the assembly stage was not done.
Re:AsmBB – a lightweight web forum engine written in assembl... by kragen on Saturday January 13, 2024 @08:57PM (#38986660)
there are compilers that do not generate textual assembly output from their ir, but gcc in particular does
Re:AsmBB – a lightweight web forum engine written in assembl... by kragen on Saturday January 13, 2024 @08:56PM (#38986651)
i suspect you mean i386, not x32; x32 is an almost unused abi added in 02011 for 64-bit amd and compatible processors, available with gcc -mx32. https://lwn.net/Articles/548838/ talks a bit about its early adoption

it's so little used that i can't find the abi documentation, but gcc -c -mx32 does seem to generate code that passes arguments in registers, not on the stack, contrary to your assertion

edit: after enough digging, i found https://web.archive.org/web/20130902094821/https://sites.goo... linking to https://web.archive.org/web/20201015005434/https://3263a7b2-... but x32-abi-1.0.pdf seems to be missing from the archive and https://web.archive.org/web/*/https://sites.google.com/site/...* doesn't look at all promising

Re:AsmBB – a lightweight web forum engine written in assembl... by pengaru on Saturday January 13, 2024 @09:00PM (#38986681)
You're right, I was sloppy in typing x32 for i386 (as you mentioned, nobody actually uses that).
Re:AsmBB – a lightweight web forum engine written in assembl... by kragen on Saturday January 13, 2024 @09:02PM (#38986683)
cool, thanks for clarifying
Re:AsmBB – a lightweight web forum engine written in assembl... by quesera on Saturday January 13, 2024 @09:38PM (#38986889)
> C is generally first compiled into assembly anyways.

Splitting hairs perhaps, but the C compiler output is machine code, right? No reason to generate assembly along the way.

Re:AsmBB – a lightweight web forum engine written in assembl... by pengaru on Saturday January 13, 2024 @10:09PM (#38987049)
> > C is generally first compiled into assembly anyways.

> Splitting hairs

> > generally

smh

https://en.wikipedia.org/wiki/Compiler#Three-stage_compiler_...