initHookRegister() make idempotent and MustSucceed

modules/libcom/src/iocsh/initHooks.c

@@ -21,6 +21,7 @@
 #include "ellLib.h"
 #include "epicsMutex.h"
 #include "epicsThread.h"
+#include "cantProceed.h"
 
 #include "initHooks.h"
 
@@ -52,19 +53,26 @@ static void initHookInit(void)
 int initHookRegister(initHookFunction func)
 {
     initHookLink *newHook;
+    ELLNODE *cur;
 
     if (!func) return 0;
 
     initHookInit();
 
-    newHook = (initHookLink *)malloc(sizeof(initHookLink));
+    epicsMutexMustLock(listLock);
-    if (!newHook) {
+
-        printf("Cannot malloc a new initHookLink\n");
+    for(cur = ellFirst(&functionList); cur; cur = ellNext(cur)) {
-        return -1;
+        const initHookLink *fn = CONTAINER(cur, initHookLink, node);
+        if(fn->func==func) {
+            /* silently ignore duplicate */
+            epicsMutexUnlock(listLock);
+            return 0;
+        }
     }
+
+    newHook = (initHookLink *)mallocMustSucceed(sizeof(initHookLink), "initHookRegister");
     newHook->func = func;
 
-    epicsMutexMustLock(listLock);
     ellAdd(&functionList, &newHook->node);
     epicsMutexUnlock(listLock);
     return 0;

modules/libcom/src/iocsh/initHooks.h

@@ -163,7 +163,11 @@ typedef void (*initHookFunction)(initHookState state);
  *
  * Registers \p func for initHook notifications
  * \param func Pointer to application's notification function.
- * \return 0 if Ok, -1 on error (memory allocation failure).
+ * \return Always zero.  (before UNRELEASED could return -1 on allocation failure)
+ *
+ * \since UNRELEASED initHookRegister is idempotent.
+ *        Previously, repeated registrations would result
+ *        in duplicate calls to the hook function.
  */
 LIBCOM_API int initHookRegister(initHookFunction func);