[clang] Enable the -Wdangling-capture diagnostic by default.

[hokein]

We have tested this diagnostics internally, and we don't find see any issues.

[llvmbot]

@llvm/pr-subscribers-clang

Author: Haojian Wu (hokein)

Changes

We have tested this diagnostics internally, and we don't find see any issues.

---

Full diff: https://github.com/llvm/llvm-project/pull/119685.diff

2 Files Affected:

• (modified) clang/docs/ReleaseNotes.rst (+9)
• (modified) clang/include/clang/Basic/DiagnosticSemaKinds.td (+2-2)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 6802c0c50b8f0c..7cb18225cb38c2 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -664,6 +664,15 @@ Improvements to Clang's diagnostics
       bool operator==(const C&) = default;
     };
 
+- Clang now emits `-Wdangling-capture` diangostic when a STL container captures a dangling reference.
+
+  .. code-block:: c++
+
+    void test() {
+      std::vector<std::string_view> views;
+      views.push_back(std::string("123")); // warning
+    }
+
 Improvements to Clang's time-trace
 ----------------------------------
 
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 0a245e2077f68f..811265151fa0da 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -10237,10 +10237,10 @@ def warn_dangling_pointer_assignment : Warning<
    InGroup<DanglingAssignment>;
 def warn_dangling_reference_captured : Warning<
    "object whose reference is captured by '%0' will be destroyed at the end of "
-   "the full-expression">, InGroup<DanglingCapture>, DefaultIgnore;
+   "the full-expression">, InGroup<DanglingCapture>;
 def warn_dangling_reference_captured_by_unknown : Warning<
    "object whose reference is captured will be destroyed at the end of "
-   "the full-expression">, InGroup<DanglingCapture>, DefaultIgnore;
+   "the full-expression">, InGroup<DanglingCapture>;
 
 // For non-floating point, expressions of the form x == x or x != x
 // should result in a warning, since these always evaluate to a constant.

[cor3ntin]

Did you benchmark the impact on compile times?

[Xazax-hun]

LGTM!

[hokein]

Did you benchmark the impact on compile times?

I don't have concrete numbers, this warning works similarly to other -Wdangling warnings, performing only a lightweight, single-statement analysis on the annotated parameter, I believe the cost on compile times is negligible.