Commit 6c2151bf authored by Pavel Labath's avatar Pavel Labath
Browse files

[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
parent b81cc603

llvm/include/llvm/ADT/ArrayRef.h

+10 −0
Original line number Diff line number Diff line
@@ -97,9 +97,19 @@ namespace llvm { 
    /*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.