Add a new flag and attributes to control static destructor registration

This commit adds the flag -fno-c++-static-destructors and the attributes
[[clang::no_destroy]] and [[clang::always_destroy]]. no_destroy specifies that a
specific static or thread duration variable shouldn't have it's destructor
registered, and is the default in -fno-c++-static-destructors mode.
always_destroy is the opposite, and is the default in -fc++-static-destructors
mode.

A variable whose destructor is disabled (either because of
-fno-c++-static-destructors or [[clang::no_destroy]]) doesn't count as a use of
the destructor, so we don't do any access checking or mark it referenced. We
also don't emit -Wexit-time-destructors for these variables.

rdar://21734598

Differential revision: https://reviews.llvm.org/D50994

llvm-svn: 340306

1 files changed, 2 insertions, 0 deletions

diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index ded2d421995..74476bbe5e3 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -2772,6 +2772,8 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
   // -fallow-editor-placeholders
   Opts.AllowEditorPlaceholders = Args.hasArg(OPT_fallow_editor_placeholders);
 
+  Opts.RegisterStaticDestructors = !Args.hasArg(OPT_fno_cxx_static_destructors);
+
   if (Arg *A = Args.getLastArg(OPT_fclang_abi_compat_EQ)) {
     Opts.setClangABICompat(LangOptions::ClangABI::Latest);