[PATCH] D74361: [Clang] Undef attribute for global variables

[Arthur O'Dwyer via Phabricator via cfe-commits]

Quuxplusone added inline comments.


================
Comment at: clang/test/CodeGenCXX/attr-loader-uninitialized.cpp:23
+// CHECK: @nominally_value_init = global i32 undef
+int nominally_value_init  [[clang::loader_uninitialized]] = 4;
+
----------------
This test case is identical to line 36 of clang/test/Sema/attr-loader-uninitialized.cpp, where you say you don't want it to compile at all.

I think you need a clearer idea of how this interacts with initializers. Is it merely supposed to eliminate the //zero-initialization// that happens before the user-specified construction/initialization, or is it supposed to compete with the user-specified construction/initialization?

That is, for

    nontrivial unt [[clang::loader_uninitialized]];

is it merely supposed to call `unt::unt()` on a chunk of undef memory (instead of the usual chunk of zeroed memory), or is it supposed to skip the constructor entirely? And for

    int x [[clang::loader_uninitialized]] = foo();

is it merely supposed to call `foo()` and assign the result to a chunk of undef memory (instead of the usual chunk of zeroed memory), or is it supposed to skip the initialization entirely?


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D74361/new/

https://reviews.llvm.org/D74361