From dea61821ebe813b08da6635e3b62c5dc09330026 Mon Sep 17 00:00:00 2001
From: Michael Tautschnig <tautschn@amazon.com>
Date: Thu, 24 Mar 2022 00:57:01 +0000
Subject: [PATCH] Add missing <functional> include

Headers should include what they, and not rely on nonstd/optional to
provide the header.
---
 src/goto-programs/resolve_inherited_component.h | 2 ++
 src/solvers/flattening/boolbv_map.h             | 5 +++--
 src/util/expr.h                                 | 2 ++
 3 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/goto-programs/resolve_inherited_component.h b/src/goto-programs/resolve_inherited_component.h
index 5063f479e5a..fc61bc77756 100644
--- a/src/goto-programs/resolve_inherited_component.h
+++ b/src/goto-programs/resolve_inherited_component.h
@@ -16,6 +16,8 @@ Author: Diffblue Ltd.
 #include <util/irep.h>
 #include <util/optional.h>
 
+#include <functional>
+
 class symbolt;
 class symbol_tablet;
 
diff --git a/src/solvers/flattening/boolbv_map.h b/src/solvers/flattening/boolbv_map.h
index 7e079e15fa7..ee6b7425955 100644
--- a/src/solvers/flattening/boolbv_map.h
+++ b/src/solvers/flattening/boolbv_map.h
@@ -10,12 +10,13 @@ Author: Daniel Kroening, kroening@kroening.com
 #ifndef CPROVER_SOLVERS_FLATTENING_BOOLBV_MAP_H
 #define CPROVER_SOLVERS_FLATTENING_BOOLBV_MAP_H
 
-#include <iosfwd>
-
 #include <util/type.h>
 
 #include <solvers/prop/literal.h>
 
+#include <functional>
+#include <iosfwd>
+
 class propt;
 
 class boolbv_mapt
diff --git a/src/util/expr.h b/src/util/expr.h
index 61b7a1caedb..6240f6c2a62 100644
--- a/src/util/expr.h
+++ b/src/util/expr.h
@@ -15,6 +15,8 @@ Author: Daniel Kroening, kroening@kroening.com
 #include "validate_types.h"
 #include "validation_mode.h"
 
+#include <functional>
+
 #define forall_operands(it, expr)                                              \
   for(exprt::operandst::const_iterator                                         \
         it = as_const(expr).operands().begin(),                                \