[llvm-bugs] [Bug 46059] New: [[gnu::used]] unsupported. Breaks many "inline static" use cases including P0424R0.

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=46059

            Bug ID: 46059
           Summary: [[gnu::used]] unsupported. Breaks many "inline static"
                    use cases including P0424R0.
           Product: clang
           Version: trunk
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++17
          Assignee: unassignedclangbugs at nondot.org
          Reporter: dsim at smallscript.com
                CC: blitzrakete at gmail.com, erik.pilkington at gmail.com,
                    llvm-bugs at lists.llvm.org, richard-llvm at metafoo.co.uk

NEVER FIXED: https://bugs.llvm.org/show_bug.cgi?id=19923

Breaks patterns for creating self registering code modules; which happens to
also go hand in hand with pattern use cases for P0424R0/P0424R1.

Using "inline static" will not ensure the static variable is defined.

In fact, the compiler will analyze and remove the static if it thinks it is
unreachable.

This creates the need to do horrible things like declare static extern export
functions that reference the "inline static" to ensure it is not elided. Which
is total crap and pollution of the COFF/ELF/PE exports!

struct Base {
  inline static Base* pHead = nullptr;
  static void DoRuntimeActions() { 
    for(auto p = pHead; p; p = p->pPrev) p->onRuntimeAction();
  }
  Base* pPrev;
  Base() { pPrev = pHead; pHead = this; }
  virtual void onRuntimeAction() = 0;
}
struct Foo : Base {
  [[gnu::used]] /* NO SUPPORTED IN CLANG!!!! */
  inline static Foo s; // SO, no way to guarantee it will exist
  /* leverage static singleton registration pattern BROKEN */
  virtual void onRuntimeAction() { /* do something useful */ }
}

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