[llvm-dev] [EXT] Should we switch to --hash-style=both by default in LLD ?

[Romain GEISSLER via llvm-dev]

Le 2 oct. 2017 à 18:37, Rui Ueyama <ruiu at google.com<mailto:ruiu at google.com>> a écrit :

Changing default to "both" is probably fine, but what does that change actually mean in practice? I believe clang already passes --hash-style=both to the linker by default.

Not exactly.

The current Linux driver (I haven't checked other ELF-based systems) reads this (https://github.com/llvm-mirror/clang/blob/master/lib/Driver/ToolChains/Linux.cpp#L228)


  // Do not use 'gnu' hash style for Mips targets because .gnu.hash
  // and the MIPS ABI require .dynsym to be sorted in different ways.
  // .gnu.hash needs symbols to be grouped by hash code whereas the MIPS
  // ABI requires a mapping between the GOT and the symbol table.
  // Android loader does not support .gnu.hash.
  // Hexagon linker/loader does not support .gnu.hash
  if (!IsMips && !IsAndroid && !IsHexagon) {
    if (Distro.IsRedhat() || Distro.IsOpenSUSE() ||
        (Distro.IsUbuntu() && Distro >= Distro::UbuntuMaverick))
      ExtraOpts.push_back("--hash-style=gnu");

    if (Distro.IsDebian() || Distro.IsOpenSUSE() || Distro == Distro::UbuntuLucid ||
        Distro == Distro::UbuntuJaunty || Distro == Distro::UbuntuKarmic)
      ExtraOpts.push_back("--hash-style=both");
  }

Given that several libc implementation supports this in the Linux ecosystem (glibc, musl, uClibc, most likely others) I think lld should provide good defaults by default, instead of relying on what some distro maintainer have hardcoded for their own distro in clang.

Cheers,
ROmain
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