Support for named and bodyless reactions in C++

core/src/main/java/org/lflang/Target.java

@@ -494,7 +494,7 @@ public boolean supportsParameterizedWidths() {
    * this target.
    */
   public boolean supportsReactionDeclarations() {
-    if (this.equals(Target.C)) return true;
+    if (this.equals(Target.C) || this.equals(Target.CPP)) return true;
     else return false;
   }
 

core/src/main/kotlin/org/lflang/ast/AstExtensions.kt

@@ -263,10 +263,11 @@ val Resource.model: Model get() = this.allContents.asSequence().filterIsInstance
 
 /** Get a label representing the receiving reaction.
  *
- * If the reaction is annotated with a label, then the label is returned. Otherwise, a reaction name
- * is generated based on its priority.
+ * If the reaction is named, then the name is returned.
+ * If it is not named but annotated with a label, then the label is returned.
+ * Otherwise, a reaction name is generated based on its priority.
  */
-val Reaction.label get(): String = AttributeUtils.getLabel(this) ?: "reaction_$priority"
+val Reaction.label get(): String = name ?: AttributeUtils.getLabel(this) ?: "reaction_$priority"
 
 /** Get the priority of a receiving reaction */
 val Reaction.priority

core/src/main/kotlin/org/lflang/generator/cpp/CppExtensions.kt

@@ -47,7 +47,7 @@ import org.lflang.lf.WidthSpec
 
 /** Get the "name" a reaction is represented with in target code.*/
 val Reaction.codeName
-    get(): String = "r$indexInContainer"
+    get(): String = name ?: "r$indexInContainer"
 
 /* **********************************************************************************************
  * C++ specific extensions shared across classes

core/src/main/kotlin/org/lflang/generator/cpp/CppReactionGenerator.kt

@@ -45,8 +45,7 @@ import org.lflang.toText
 /** A C++ code generator for reactions and their function bodies */
 class CppReactionGenerator(
     private val reactor: Reactor,
-    private val portGenerator: CppPortGenerator,
-    private val instanceGenerator: CppInstanceGenerator
+    private val portGenerator: CppPortGenerator
 ) {
 
     private val reactionsWithDeadlines = reactor.reactions.filter { it.deadline != null }
@@ -149,8 +148,9 @@ class CppReactionGenerator(
         }
     }
 
-    private fun generateBodyDefinition(reaction: Reaction): String {
-        return with(PrependOperator) {
+    private fun generateBodyDefinition(reaction: Reaction): String? {
+        return if (reaction.code == null) null
+        else with(PrependOperator) {
             """
                 |// reaction ${reaction.label}
                 |${reactor.templateLine}
@@ -253,7 +253,7 @@ class CppReactionGenerator(
 
     /** Get all definitions of reaction bodies. */
     fun generateBodyDefinitions() =
-        reactor.reactions.joinToString(separator = "\n", postfix = "\n") { generateBodyDefinition(it) }
+        reactor.reactions.mapNotNull { generateBodyDefinition(it) }.joinToString(separator = "\n", postfix = "\n")
 
     /** Get all declarations of deadline handlers. */
     fun generateDeadlineHandlerDeclarations(): String =

core/src/main/kotlin/org/lflang/generator/cpp/CppReactorGenerator.kt

@@ -54,7 +54,7 @@ class CppReactorGenerator(private val reactor: Reactor, fileConfig: CppFileConfi
     private val timers = CppTimerGenerator(reactor)
     private val actions = CppActionGenerator(reactor, messageReporter)
     private val ports = CppPortGenerator(reactor)
-    private val reactions = CppReactionGenerator(reactor, ports, instances)
+    private val reactions = CppReactionGenerator(reactor, ports)
     private val assemble = CppAssembleMethodGenerator(reactor)
 
     private fun publicPreamble() =

test/Cpp/src/HelloBodylessWorld.lf

@@ -0,0 +1,7 @@
+target Cpp {
+  cmake-include: hello_bodyless_world.cmake
+}
+
+main reactor {
+  reaction hello(startup)
+}

test/Cpp/src/hello_bodyless_world.cc

@@ -0,0 +1,5 @@
+#include "HelloBodylessWorld/HelloBodylessWorld.hh"
+
+void HelloBodylessWorld::Inner::hello_body([[maybe_unused]] const reactor::StartupTrigger& startup) {
+  std::cout << "Hello World." << std::endl;
+}

test/Cpp/src/hello_bodyless_world.cmake

@@ -0,0 +1,3 @@
+target_sources(${LF_MAIN_TARGET} PRIVATE ${CMAKE_CURRENT_LIST_DIR}/hello_bodyless_world.cc)
+
+