[mattpallissard]

> How to do this is documented only in the middle of a dusty ld manual nobody has ever read.

This got an audible laugh out of me.

> Good platforms allow you to build on newer versions whilst targeting older versions.

I haven't been doing this for 20 years (13), but I've written a fair amount of C. This, among other things, is what made me start dabbling with zig.

  ~  gcc -o foo foo.c
  ~  du -sh foo
  16K foo
  ~  readelf -sW foo | grep 'GLIBC' | sort -h
       1: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND __libc_start_main@GLIBC_2.34 (2)
       3: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND puts@GLIBC_2.2.5 (3)
       6: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND __libc_start_main@GLIBC_2.34
       6: 0000000000000000     0 FUNC    WEAK   DEFAULT  UND __cxa_finalize@GLIBC_2.2.5 (3)
       9: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND puts@GLIBC_2.2.5
      22: 0000000000000000     0 FUNC    WEAK   DEFAULT  UND __cxa_finalize@GLIBC_2.2.5
  ~  ldd foo                                 
    linux-vdso.so.1 (0x00007ffc1cbac000)
    libc.so.6 => /usr/lib/libc.so.6 (0x00007f9c3a849000)
    /lib64/ld-linux-x86-64.so.2 => /usr/lib64/ld-linux-x86-64.so.2 (0x00007f9c3aa72000)


  ~  zig cc -target x86_64-linux-gnu.2.5 foo.c -o foo
  ~  du -sh foo
  8.0K  foo
  ~  readelf -sW foo | grep 'GLIBC' | sort -h        
       1: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND __libc_start_main@GLIBC_2.2.5 (2)
       3: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND printf@GLIBC_2.2.5 (2)
  ~  ldd foo                                 
    linux-vdso.so.1 (0x00007ffde2a76000)
    libc.so.6 => /usr/lib/libc.so.6 (0x0000718e94965000)
    /lib64/ld-linux-x86-64.so.2 => /usr/lib64/ld-linux-x86-64.so.2 (0x0000718e94b89000)

edit: I haven't built anything complicated with zig as I have with the other c build systems, but so far it seems to have some legit quality of life improvements.

[mike_hearn]

Interesting that zig does this. I wonder what the binaries miss out on by defaulting to such an old symbol version. That's part of the problem of course: finding that out requires reverse engineering the glibc source code.

[fch42]

Maybe just nitpicking but he _specified_ the target version for the zig compile.

(Haven't tested what it would link against where that not given)

[mattpallissard]

> Maybe just nitpicking but he _specified_ the target version for the zig compile.

Right, but I was able to do it as a whole. I didn't have to do it per symbol.