sim/cgen: mask uninitialized variable warning in cgen-run.c

I see an uninitialized variable warning (with gcc 9.3.1) from
cgen-run.c, like this:

  /tmp/build/sim/../../src/sim/cris/../common/cgen-run.c: In function ‘sim_resume’:
  /tmp/build/sim/../../src/sim/cris/../common/cgen-run.c:259:5: warning: ‘engine_fns$’ may be used uninitialized in this function [-Wmaybe-uninitialized]
    259 |    (* engine_fns[next_cpu_nr]) (cpu);
        |    ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  /tmp/build/sim/../../src/sim/cris/../common/cgen-run.c:232:14: note: ‘engine_fns$’ was declared here
    232 |   ENGINE_FN *engine_fns[MAX_NR_PROCESSORS];
        |              ^~~~~~~~~~

This is a false positive - we over allocate engine_fn, and then only
initialize the nr_cpus entries which we will later go on to use.

However, we can easily silence this warning by initializing the unused
entries in engine_fns to NULL, this might also help if anyone ever
looks at engine_fns in a debugger, it should now be obvious which
entries are in use, and which are not.

With this change the warning is gone.

There should be no change in behaviour with this commit.

diff --git a/sim/common/cgen-run.c b/sim/common/cgen-run.c
index 9a13b0ca41659b49289f2c3d0c49d51fc1837ddc..a9a493c01b9fe7f5348f6e95884b281c752d80c8 100644 (file)
--- a/sim/common/cgen-run.c
+++ b/sim/common/cgen-run.c
@@ -242,6 +242,11 @@ engine_run_n (SIM_DESC sd, int next_cpu_nr, int nr_cpus, int max_insns, int fast
       prime_cpu (cpu, max_insns);
     }
 
+  /* Ensure the remaining engine_fns slots are initialized, this silences a
+     compiler warning when engine_fns is used below.  */
+  for (i = nr_cpus; i < MAX_NR_PROCESSORS; ++i)
+    engine_fns[i] = NULL;
+
   while (1)
     {
       SIM_ENGINE_PREFIX_HOOK (sd);