[PATCH] D103495: [static initializers] Emit global_ctors and global_dtors in reverse order when init_array is not used.

[James Y Knight via Phabricator via llvm-commits]

jyknight added a comment.

Won't this change cause weird effects with LTO, when you're merging multiple TUs' global_ctors arrays before emitting? Won't this end up reversing the order of the files, as well as the order of the functions within a single file? That does not seem likely to be expected, right?

> The compiler knows which scheme is in use and it is controlled by -fuse-init-array.

This isn't exactly true -- the linker (binutils ld and ld.gold) can translate ctors to init_array, so we also need to look at what they do. I can't actually find the code that does it in bfd, but in examination of its output, it looks like it does reverse the order of pointers within a ctors section when translating to init_array, in order to preserve the expected "backwards" order that ctors users "wanted". And gold does the same -- except it  is buggy, because it reverses the order of the text itself, yet not the relocation entries associated with it. So depending on whether you're building a PIC binary or not, you get different behavior (sigh). Anyhow, modulo that gold bug, it looks like this is actually OK.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D103495/new/

https://reviews.llvm.org/D103495