[lld] [LLD][ELF] Assert TargetInfo correctness for when ctx becomes a local (PR #111139)

[via llvm-commits]

https://github.com/bd1976bris created https://github.com/llvm/llvm-project/pull/111139

TargetInfos are currently function-statics, e.g: https://github.com/llvm/llvm-project/blob/6294679faa8ae57873b7fcdc00a4deb522d31c38/lld/ELF/Arch/X86_64.cpp#L1257.

Add an assert to Guard against that causing problems if ctx is changed from a global variable to a local variable.

>From aa8daf044ecdbf60df412295ea5005ccf0c697bb Mon Sep 17 00:00:00 2001
From: bd1976bris <bd1976llvm at gmail.com>
Date: Fri, 4 Oct 2024 13:08:07 +0100
Subject: [PATCH] [LLD][ELF] Add assert for TargetInfo correctness for when ctx
 becomes a local variable

TargetInfos are currently function-statics.

Add an assert to Guard against that causing problems if ctx is changed from a global variable to a local variable.
---
 lld/ELF/Driver.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lld/ELF/Driver.cpp b/lld/ELF/Driver.cpp
index 373505a9e965b7..5042c23fd7b07e 100644
--- a/lld/ELF/Driver.cpp
+++ b/lld/ELF/Driver.cpp
@@ -3123,6 +3123,10 @@ template <class ELFT> void LinkerDriver::link(opt::InputArgList &args) {
   // relocations or writing a PLT section. It also contains target-dependent
   // values such as a default image base address.
   ctx.target = getTarget(ctx);
+  // Currently, the TargetInfo structures in are function-statics. Guard against
+  // that causing problems if ctx is changed from a global variable to a local
+  // variable.
+  assert(&ctx.target->ctx == &ctx);
 
   ctx.arg.eflags = ctx.target->calcEFlags();
   // maxPageSize (sometimes called abi page size) is the maximum page size that