Is it possible to link to glibc < 2.16?

[skep1337]

When I run the following:
cargo-zigbuild b -r --target x86_64-unknown-linux-gnu.2.15 -Z build-std

I get the error
ld.lld: error: undefined symbol: getauxval

Would it be possible to just "substitute" the 'getauxval' call with de-abstracted code?

[messense]

Donno, maybe you can achieve that by using a linker script: https://mcyoung.xyz/2021/06/01/linker-script/#linker-symbols, but IMO it should be fixed in code to not use the symbol if it's unavailable, if the Rust std src uses it unconditionally, consider patch it locally as glibc < 2.17 is not supported by Rust now.

[skep1337]

So I found a very trivial patch for this, which allows linking down to libc 2.12

In the std source file:
/home/user/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/pal/unix/stack_overflow.rs

The only call to 'getauxval()' is on line 268
let dynamic_sigstksz = unsafe { libc::getauxval(libc::AT_MINSIGSTKSZ) };

If you just simply set this variable to 0, it removes the need for the call to 'getauxval()' and changes seemingly nothing
let dynamic_sigstksz = 0;

It's even meant to return 0 if it's unable to get a value
// If getauxval couldn't find the entry, it returns 0,