Add C code generation to store currently executed reaction, add AnytimePrime.lf as a demo for check_deadline().

experimental/C/src/AnytimePrime.lf

@@ -0,0 +1,67 @@
+/**
+ * This program is a concept demonstration showing how the check_deadline()
+ * function works. This program performs "anytime computation" (https://en.wikipedia.org/wiki/Anytime_algorithm)
+ * to find the largest prime within the given deadline. The check_deadline()
+ * function is called after checking each number if it is prime. If the
+ * check_deadline() is called after the deadline has passed, the function calls
+ * the deadline handler and returns true. Then the program outputs the largest
+ * prime found by that time and exits.
+ *
+ * For more discussion on check_deadline(), see: https://github.com/lf-lang/lingua-franca/issues/403
+ *
+ * @author Hokeun Kim ([email protected])
+ * @author Edward A. Lee ([email protected])
+ * @author Marten Lohstroh ([email protected])
+ */
+target C {
+    fast: true,
+    files: ["/lib/c/reactor-c/core/utils/vector.h",
+            "/lib/c/reactor-c/core/utils/vector.c"]
+};
+
+preamble {=
+#include "vector.c"
+=}
+
+reactor Prime {
+    output out:{=long long=};
+    reaction(startup) -> out {=
+    int num_primes = 1;
+    long long current_num = 2;
+    vector_t primes = vector_new(10000);
+    vector_push(&primes, (void*)2);
+
+    while (!check_deadline(self)) {
+        current_num++;
+        int i = 0;
+        for (i = 0; i < num_primes; i++) {
+            if (current_num % (long long)primes.start[i] == 0) {
+                break;
+            }
+        }
+        if (i == num_primes) {
+            // Add the prime to vector.
+            vector_push(&primes, (void*)current_num);
+            num_primes++;
+        }
+    }
+
+    // Output the largest prime found.
+    SET(out, (long long)primes.start[num_primes - 1]);
+    =} deadline (3 sec) {=
+        info_print("Deadline handler called!");
+    =}
+}
+
+reactor Print {
+    input in:int;
+    reaction(in) {=
+        printf("Largest prime found within the deadline: %d\n", in->value);
+    =}
+}
+
+main reactor AnytimePrime {
+    p = new Prime();
+    d = new Print();
+    p.out -> d.in;
+}

org.lflang/src/org/lflang/generator/c/CGenerator.xtend

@@ -2772,6 +2772,7 @@ class CGenerator extends GeneratorBase {
                  #pragma GCC diagnostic push
                  #pragma GCC diagnostic ignored "-Wunused-variable"
                  «structType»* self = («structType»*)instance_args;
+                 ((self_base_t*)self)->executing_reaction = &self->_lf__reaction_«reactionIndex»;
              ''')
         }