[LifetimeSafety] Add language option for experimental lifetime safety…

[usx95]

Add a language option flag for experimental lifetime safety analysis in C++.

This change provides a language option to control the experimental lifetime safety analysis feature, making it more explicit and easier to enable/disable. Previously, the feature was controlled indirectly through a diagnostic warning flag, which we do not want to accidentally enable with -Weverything (atm)!

• Added a new language option EnableLifetimeSafety in LangOptions.def for experimental lifetime safety analysis in C++
• Added corresponding driver options -fexperimental-lifetime-safety and -fno-experimental-lifetime-safety in Options.td
• Modified AnalysisBasedWarnings.cpp to use the new language option flag instead of checking if a specific diagnostic is ignored
• Updated a test case to use the new flag instead of relying on the warning flag alone

(cherry picked from commit 0d04789)
Fixes #149537

[llvmbot]

@llvm/pr-subscribers-clang

Author: Utkarsh Saxena (usx95)

Changes

… (#149592)

Add a language option flag for experimental lifetime safety analysis in C++.

This change provides a language option to control the experimental lifetime safety analysis feature, making it more explicit and easier to enable/disable. Previously, the feature was controlled indirectly through a diagnostic warning flag, which we do not want to accidentally enable with -Weverything (atm)!

• Added a new language option EnableLifetimeSafety in LangOptions.def for experimental lifetime safety analysis in C++
• Added corresponding driver options -fexperimental-lifetime-safety and -fno-experimental-lifetime-safety in Options.td
• Modified AnalysisBasedWarnings.cpp to use the new language option flag instead of checking if a specific diagnostic is ignored
• Updated a test case to use the new flag instead of relying on the warning flag alone

(cherry picked from commit 0d04789)
Fixes: #149537

---

Full diff: https://github.com/llvm/llvm-project/pull/152027.diff

4 Files Affected:

• (modified) clang/include/clang/Basic/LangOptions.def (+2)
• (modified) clang/include/clang/Driver/Options.td (+8)
• (modified) clang/lib/Sema/AnalysisBasedWarnings.cpp (+1-2)
• (modified) clang/test/Sema/warn-lifetime-safety-dataflow.cpp (+1-1)

diff --git a/clang/include/clang/Basic/LangOptions.def b/clang/include/clang/Basic/LangOptions.def
index 0d546cb3b8471..f5a5d84eefb80 100644
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -496,6 +496,8 @@ LANGOPT(CheckConstexprFunctionBodies, 1, 1, Benign,
 
 LANGOPT(BoundsSafety, 1, 0, NotCompatible, "Bounds safety extension for C")
 
+LANGOPT(EnableLifetimeSafety, 1, 0, NotCompatible, "Experimental lifetime safety analysis for C++")
+
 LANGOPT(PreserveVec3Type, 1, 0, NotCompatible, "Preserve 3-component vector type")
 
 #undef LANGOPT
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index bce29a76f3ac7..18e4ab406ce4e 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -1917,6 +1917,14 @@ defm bounds_safety : BoolFOption<
   BothFlags<[], [CC1Option],
           " experimental bounds safety extension for C">>;
 
+defm lifetime_safety : BoolFOption<
+  "experimental-lifetime-safety",
+  LangOpts<"EnableLifetimeSafety">, DefaultFalse,
+  PosFlag<SetTrue, [], [CC1Option], "Enable">,
+  NegFlag<SetFalse, [], [CC1Option], "Disable">,
+  BothFlags<[], [CC1Option],
+          " experimental lifetime safety for C++">>;
+
 defm addrsig : BoolFOption<"addrsig",
   CodeGenOpts<"Addrsig">, DefaultFalse,
   PosFlag<SetTrue, [], [ClangOption, CC1Option], "Emit">,
diff --git a/clang/lib/Sema/AnalysisBasedWarnings.cpp b/clang/lib/Sema/AnalysisBasedWarnings.cpp
index 85ac3c06ec2c2..ec39bca6039f0 100644
--- a/clang/lib/Sema/AnalysisBasedWarnings.cpp
+++ b/clang/lib/Sema/AnalysisBasedWarnings.cpp
@@ -2891,8 +2891,7 @@ void clang::sema::AnalysisBasedWarnings::IssueWarnings(
       .setAlwaysAdd(Stmt::UnaryOperatorClass);
   }
 
-  bool EnableLifetimeSafetyAnalysis = !Diags.isIgnored(
-      diag::warn_experimental_lifetime_safety_dummy_warning, D->getBeginLoc());
+  bool EnableLifetimeSafetyAnalysis = S.getLangOpts().EnableLifetimeSafety;
   // Install the logical handler.
   std::optional<LogicalErrorHandler> LEH;
   if (LogicalErrorHandler::hasActiveDiagnostics(Diags, D->getBeginLoc())) {
diff --git a/clang/test/Sema/warn-lifetime-safety-dataflow.cpp b/clang/test/Sema/warn-lifetime-safety-dataflow.cpp
index 38dfdb98f08fc..a956386ae9332 100644
--- a/clang/test/Sema/warn-lifetime-safety-dataflow.cpp
+++ b/clang/test/Sema/warn-lifetime-safety-dataflow.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -mllvm -debug-only=LifetimeFacts,LifetimeDataflow -Wexperimental-lifetime-safety %s 2>&1 | FileCheck %s
+// RUN: %clang_cc1 -fexperimental-lifetime-safety -mllvm -debug-only=LifetimeFacts,LifetimeDataflow -Wexperimental-lifetime-safety %s 2>&1 | FileCheck %s
 // REQUIRES: asserts
 
 struct MyObj {