[flang-commits] [flang] [flang][bbc] Fix dangling reference to `envDefaults` (PR #82800)

[Krzysztof Parzyszek via flang-commits]

https://github.com/kparzysz created https://github.com/llvm/llvm-project/pull/82800

The lowering bridge stores the evvironment defaults (passed to the constructor) as a reference. In the call to the constructor in bbc, the defaults were passed as `{}`, which creates a temporary whose lifetime ends immediately after the call.

The flang driver passes a member of the compilation instance to the constructor, which presumably remains alive long enough, so storing the reference in the bridge is justified. To avoid the dangling reference, create an actual object `envDefaults` in bbc.

>From 23722d0d3a68aae751c3f2b5491f61888ac1925d Mon Sep 17 00:00:00 2001
From: Krzysztof Parzyszek <Krzysztof.Parzyszek at amd.com>
Date: Fri, 23 Feb 2024 11:16:05 -0600
Subject: [PATCH] [flang][bbc] Fix dangling reference to `envDefaults`

The lowering bridge stores the evvironment defaults (passed to the
constructor) as a reference. In the call to the constructor in bbc,
the defaults were passed as `{}`, which creates a temporary whose
lifetime ends immediately after the call.

The flang driver passes a member of the compilation instance to the
constructor, which presumably remains alive long enough, so storing
the reference in the bridge is justified. To avoid the dangling
reference, create an actual object `envDefaults` in bbc.
---
 flang/tools/bbc/bbc.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/flang/tools/bbc/bbc.cpp b/flang/tools/bbc/bbc.cpp
index c9358c83e795c4..e701fdeb227a40 100644
--- a/flang/tools/bbc/bbc.cpp
+++ b/flang/tools/bbc/bbc.cpp
@@ -354,10 +354,11 @@ static mlir::LogicalResult convertFortranSourceToMLIR(
   loweringOptions.setPolymorphicTypeImpl(enablePolymorphic);
   loweringOptions.setNoPPCNativeVecElemOrder(enableNoPPCNativeVecElemOrder);
   loweringOptions.setLowerToHighLevelFIR(useHLFIR || emitHLFIR);
+  std::vector<Fortran::lower::EnvironmentDefault> envDefaults = {};
   auto burnside = Fortran::lower::LoweringBridge::create(
       ctx, semanticsContext, defKinds, semanticsContext.intrinsics(),
       semanticsContext.targetCharacteristics(), parsing.allCooked(),
-      targetTriple, kindMap, loweringOptions, {},
+      targetTriple, kindMap, loweringOptions, envDefaults,
       semanticsContext.languageFeatures(), targetMachine);
   burnside.lower(parseTree, semanticsContext);
   mlir::ModuleOp mlirModule = burnside.getModule();