7 ms·

Writing device drivers in C, and then using the -S flag ... have you seen the output gcc -S on Linux (Ubuntu) returns for a trivial hello world program? ;)

jacquesm 17y ago
Sure. And for non-trivial programs as well. Low level assembly is what you want, that presumably includes interfacing with you favorite C code. Calling conventions, stack frames and so on. Besides, the boilerplate runtime stuff has nothing to do with writing kernel code, so a 'trivial hello world' program will have a lot of cruft added to it: .file "hello.c" .section .rodata .LC0: .string "helo, world!" .text .globl main .type main, @function main: leal 4(%esp), %ecx andl $-16, %esp pushl -4(%ecx) pushl %ebp movl %esp, %ebp pushl %ecx subl $20, %esp movl $.LC0, (%esp) call puts addl $20, %esp popl %ecx popl %ebp leal -4(%ecx), %esp ret .size main, .-main .ident "GCC: (Ubuntu 4.3.3-5ubuntu4) 4.3.3" .section .note.GNU-stack,"",@progbits that's not that bad. Note the stack frame alignment trick, the fact that 'printf' was specified in the source but puts is being called!
- ismarc 17y ago
  The -S flag was invaluable for me when I was moving from C to assembly. Then again, I used it in an iterative fashion, do something simple -S, do the same thing -S -O1, -S -O2, -S O3, and then a spattering of the different optimization techniques to see how it converted the C to assembly. I miss those days (did I just admit to being old?).
  - jacquesm 17y ago
    Well I'll admit it right along with you, I miss those days too. I think I must have coded myself to the moon and back by now if you'd print it all out on fanfold paper (in C, mostly), but the joy of getting a little OS to boot up from nothing is never going to pale in comparison to installing framework X and building some web-app. No matter how successful. Web-apps make substantially more $ though...

jacquesm 17y ago

Sure. And for non-trivial programs as well. Low level assembly is what you want, that presumably includes interfacing with you favorite C code. Calling conventions, stack frames and so on. Besides, the boilerplate runtime stuff has nothing to do with writing kernel code, so a 'trivial hello world' program will have a lot of cruft added to it: .file "hello.c" .section .rodata .LC0: .string "helo, world!" .text .globl main .type main, @function main: leal 4(%esp), %ecx andl $-16, %esp pushl -4(%ecx) pushl %ebp movl %esp, %ebp pushl %ecx subl $20, %esp movl $.LC0, (%esp) call puts addl $20, %esp popl %ecx popl %ebp leal -4(%ecx), %esp ret .size main, .-main .ident "GCC: (Ubuntu 4.3.3-5ubuntu4) 4.3.3" .section .note.GNU-stack,"",@progbits that's not that bad. Note the stack frame alignment trick, the fact that 'printf' was specified in the source but puts is being called!

ismarc 17y ago
The -S flag was invaluable for me when I was moving from C to assembly. Then again, I used it in an iterative fashion, do something simple -S, do the same thing -S -O1, -S -O2, -S O3, and then a spattering of the different optimization techniques to see how it converted the C to assembly. I miss those days (did I just admit to being old?).
- jacquesm 17y ago
  Well I'll admit it right along with you, I miss those days too. I think I must have coded myself to the moon and back by now if you'd print it all out on fanfold paper (in C, mostly), but the joy of getting a little OS to boot up from nothing is never going to pale in comparison to installing framework X and building some web-app. No matter how successful. Web-apps make substantially more $ though...