From a1c1525ecad11b57170fbf905baeda205cc7eb52 Mon Sep 17 00:00:00 2001
From: Axel Huebl <axel.huebl@plasma.ninja>
Date: Sat, 16 Mar 2024 16:04:15 -0700
Subject: [PATCH 1/2] Explicit Includes: MultiFab -> BaseFab (#3802)

## Summary

Add includes for directly used types.

## Additional background

Related to #3798, I was wondering if there might be an missing include
to `BaseFab<double>::lockAdd` and `AMReX_OpenMP.H` somewhere... In the
end this is just cleaning.

## Checklist

The proposed changes:
- [ ] fix a bug or incorrect behavior in AMReX
- [ ] add new capabilities to AMReX
- [ ] changes answers in the test suite to more than roundoff level
- [ ] are likely to significantly affect the results of downstream AMReX
users
- [ ] include documentation in the code and/or rst files, if appropriate
---
 Src/Base/AMReX_FabArray.H     | 7 +++++--
 Src/Base/AMReX_FabArrayBase.H | 2 ++
 Src/Base/AMReX_MultiFab.H     | 1 +
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/Src/Base/AMReX_FabArray.H b/Src/Base/AMReX_FabArray.H
index 56300d4cfef..70b2ba533c9 100644
--- a/Src/Base/AMReX_FabArray.H
+++ b/Src/Base/AMReX_FabArray.H
@@ -24,6 +24,7 @@
 #include <AMReX_MakeType.H>
 #include <AMReX_TypeTraits.H>
 #include <AMReX_LayoutData.H>
+#include <AMReX_BaseFab.H>
 #include <AMReX_BaseFabUtility.H>
 #include <AMReX_MFParallelFor.H>
 #include <AMReX_TagParallelFor.H>
@@ -39,14 +40,16 @@
 #include <omp.h>
 #endif
 
+#include <algorithm>
 #include <cstring>
 #include <limits>
 #include <map>
+#include <memory>
 #include <utility>
-#include <vector>
-#include <algorithm>
 #include <set>
 #include <string>
+#include <vector>
+
 
 namespace amrex {
 
diff --git a/Src/Base/AMReX_FabArrayBase.H b/Src/Base/AMReX_FabArrayBase.H
index 21029eff840..09dfd5e22db 100644
--- a/Src/Base/AMReX_FabArrayBase.H
+++ b/Src/Base/AMReX_FabArrayBase.H
@@ -15,9 +15,11 @@
 #include <omp.h>
 #endif
 
+#include <ostream>
 #include <string>
 #include <utility>
 
+
 namespace amrex {
 
 class MFIter;
diff --git a/Src/Base/AMReX_MultiFab.H b/Src/Base/AMReX_MultiFab.H
index fdf2e67cbd8..91e278308ea 100644
--- a/Src/Base/AMReX_MultiFab.H
+++ b/Src/Base/AMReX_MultiFab.H
@@ -4,6 +4,7 @@
 #include <AMReX_Config.H>
 
 #include <AMReX_BLassert.H>
+#include <AMReX_BaseFab.H>
 #include <AMReX_FArrayBox.H>
 #include <AMReX_FabArray.H>
 #include <AMReX_FabArrayUtility.H>

From 54e438a0b67b3cb2a8b3fc6184921e5909fbb05e Mon Sep 17 00:00:00 2001
From: David Grote <grote1@llnl.gov>
Date: Sat, 16 Mar 2024 16:09:09 -0700
Subject: [PATCH 2/2] In allocateSlice, handle empty list of boxes (#3808)

## Summary
In `allocateSlice` (which is called by `get_slice_data` in
`Src/Base/AMReX_MultiFabUtil.cpp`) handle the case when no intersection
is found between the slice and the box array.

## Additional background
When no intersection is found, the `boxes` array will be empty which
would cause a segfault if the `data` would be accessed. The fix is to
return `nullptr` in this case.
Also, `get_slice_data` is modified to return `nullptr` in this case as
well.

## Checklist

The proposed changes:
- [x] fix a bug or incorrect behavior in AMReX
- [ ] add new capabilities to AMReX
- [ ] changes answers in the test suite to more than roundoff level
- [ ] are likely to significantly affect the results of downstream AMReX
users
- [ ] include documentation in the code and/or rst files, if appropriate
---
 Src/Base/AMReX_MultiFabUtil.cpp | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/Src/Base/AMReX_MultiFabUtil.cpp b/Src/Base/AMReX_MultiFabUtil.cpp
index 27efbffca0f..5dd97fa6536 100644
--- a/Src/Base/AMReX_MultiFabUtil.cpp
+++ b/Src/Base/AMReX_MultiFabUtil.cpp
@@ -46,11 +46,15 @@ namespace {
             boxes.push_back(is.second);
             slice_to_full_ba_map.push_back(is.first);
         }
-        BoxArray slice_ba(boxes.data(), static_cast<int>(boxes.size()));
-        DistributionMapping slice_dmap(std::move(procs));
-
-        return std::make_unique<MultiFab>(slice_ba, slice_dmap, ncomp, 0,
-                                          MFInfo(), FArrayBoxFactory());
+        if (!boxes.empty()) {
+            BoxArray slice_ba(boxes.data(), static_cast<int>(boxes.size()));
+            DistributionMapping slice_dmap(std::move(procs));
+
+            return std::make_unique<MultiFab>(slice_ba, slice_dmap, ncomp, 0,
+                                              MFInfo(), FArrayBoxFactory());
+        } else {
+            return nullptr;
+        }
     }
 }
 
@@ -560,6 +564,10 @@ namespace amrex
         Vector<int> slice_to_full_ba_map;
         std::unique_ptr<MultiFab> slice = allocateSlice(dir, cc, ncomp, geom, coord, slice_to_full_ba_map);
 
+        if (!slice) {
+            return nullptr;
+        }
+
 #ifdef AMREX_USE_OMP
 #pragma omp parallel if (Gpu::notInLaunchRegion())
 #endif