fix unsilenceable warnings on GCC 9 (#41)
See issue https://github.com/rust-lang/rust/issues/69078 for details
---
[cmake] Disable GCC 9's -Winit-list-lifetime warning in ArrayRef
Summary:
This is a new warning which fires when one stores a reference to the
initializer_list contents in a way which may outlive the
initializer_list which it came from. In llvm this warning is triggered
whenever someone uses the initializer_list ArrayRef constructor.
This is indeed a dangerous thing to do (I myself was bitten by that at
least once), but it is not more dangerous than calling other ArrayRef
constructors with temporary objects -- something which we are used to
and have accepted as a tradeoff for ArrayRef's efficiency.
Currently, this warnings generates so much output that it completely
obscures any actionable warnings, so this patch disables it.
Reviewers: rnk, aaron.ballman
Subscribers: mgorny, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D70122
(cherry picked from commit 6c2151bf4c829958891e65a4cc396daa6d308eb0)
Co-authored-by: Pavel Labath <pavel@labath.sk>
diff --git a/llvm/include/llvm/ADT/ArrayRef.h b/llvm/include/llvm/ADT/ArrayRef.h
index 773c88f7..db1ff3b 100644
--- a/llvm/include/llvm/ADT/ArrayRef.h
+++ b/llvm/include/llvm/ADT/ArrayRef.h
@@ -97,9 +97,19 @@
/*implicit*/ constexpr ArrayRef(const T (&Arr)[N]) : Data(Arr), Length(N) {}
/// Construct an ArrayRef from a std::initializer_list.
+#if LLVM_GNUC_PREREQ(9, 0, 0)
+// Disable gcc's warning in this constructor as it generates an enormous amount
+// of messages. Anyone using ArrayRef should already be aware of the fact that
+// it does not do lifetime extension.
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Winit-list-lifetime"
+#endif
/*implicit*/ ArrayRef(const std::initializer_list<T> &Vec)
: Data(Vec.begin() == Vec.end() ? (T*)nullptr : Vec.begin()),
Length(Vec.size()) {}
+#if LLVM_GNUC_PREREQ(9, 0, 0)
+#pragma GCC diagnostic pop
+#endif
/// Construct an ArrayRef<const T*> from ArrayRef<T*>. This uses SFINAE to
/// ensure that only ArrayRefs of pointers can be converted.