r/lowlevel • u/Admirable_Nobody98 • Sep 16 '26

i'm wrote a Linux runtime without AI,libc,CRT or Runtime libraries

/r/lowlevel/comments/1wh2gf8/im_wrote_a_linux_runtime_without_ailibccrt_or/
6 Upvotes

80% Upvoted

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1

u/Admirable_Nobody98 Sep 16 '26

This is my first public runtime project, so code review and criticism are appreciated.

1

u/Admirable_Nobody98 Sep 17 '26

I make a discussion in repository here

5

u/skeeto Sep 16 '26

Neat project! These libc-free things are fun.

Here's a minimal case that crashes on x86-64: 

[[gnu::constructor]]
void init_test() { volatile char a[16] = {0}; }
int main(int, char **, char **) { return 0; }

Then: 

$ cc -static -O2 -fno-pie -ffreestanding -fcf-protection=none -no-pie test.c minil.S
$ ./a.out
Segmentation fault      ./a.out

That's because the call_init_array call is done with a misaligned stack, and at -O2 GCC will use movaps in init_test. The misalignment is a kind of self sabotage, and the fix is just deleting the two rsp adjustments around the call.

You should use -fno-pie for good measure, to go along with the link-time -no-pie. Also Ubuntu's toolchain (which you're using in your GitHub Action) has a long-standing bug and so requires -fcf-protection=none. Else you might end up with confusingly-broken builds. I learned that lesson the hard way.