allow to load the same alias multiple times (unless dbRecordsOnceOnly is set)

documentation/RELEASE_NOTES.md

@@ -32,6 +32,13 @@ not propagate AMSG, either.
 Channel Access links do not propagate AMSG, regardless of the MSS attribute,
 because the message is not available over Channel Access.
 
+### Allow to load the same alias multiple times
+
+Aliases can now be defined multiple times as long as they still refer to the
+same record, unless the shell variable dbRecordsOnceOnly is set.
+This allows to load database files multiple times, even if they contain
+alias definitions.
+
 ### DBE_PROPERTY event rate changed
 
 Updating property fields now only post DBE_PROPERTY events if the

modules/database/src/ioc/dbStatic/dbLexRoutines.c

@@ -1263,24 +1263,50 @@ static void dbRecordInfo(char *name, char *value)
     }
 }
 
+static long createAlias(DBENTRY *pdbentry, const char *alias)
+{
+    DBENTRY tempEntry;
+    long status;
+    dbRecordNode *precnode = pdbentry->precnode;
+
+    if (precnode->aliasedRecnode) precnode = precnode->aliasedRecnode;
+    dbInitEntry(pdbentry->pdbbase, &tempEntry);
+    status = dbFindRecord(&tempEntry, alias);
+    if (status == 0) {
+        if (tempEntry.precnode->aliasedRecnode != precnode) {
+            if (tempEntry.precnode->aliasedRecnode)
+                fprintf(stderr, ERL_ERROR ": Alias \"%s\" for \"%s\": name already used by an alias for \"%s\"\n",
+                            alias, dbGetRecordName(pdbentry),
+                            tempEntry.precnode->aliasedRecnode->recordname);
+            else
+                fprintf(stderr, ERL_ERROR ": Alias \"%s\" for \"%s\": name already used by a record\n",
+                            alias, dbGetRecordName(pdbentry));
+            status = S_dbLib_recExists;
+        } else if (dbRecordsOnceOnly) {
+            fprintf(stderr, ERL_ERROR ": Alias \"%s\" already defined and dbRecordsOnceOnly set.\n",
+                alias);
+            status = S_dbLib_recExists;
+        }
+    } else {
+        status = dbCreateAlias(pdbentry, alias);
+    }
+    dbFinishEntry(&tempEntry);
+    return status;
+}
+
 static void dbRecordAlias(char *name)
 {
     DBENTRY *pdbentry;
     tempListNode *ptempListNode;
-    long status;
-
     if(dbRecordNameValidate(name))
         return;
 
     if (duplicate) return;
     ptempListNode = (tempListNode *)ellFirst(&tempList);
     pdbentry = ptempListNode->item;
-    status = dbCreateAlias(pdbentry, name);
-    if (status) {
-        fprintf(stderr, "Can't create alias \"%s\" for \"%s\"\n",
-                    name, dbGetRecordName(pdbentry));
+
+    if (createAlias(pdbentry, name) != 0) {
         yyerror(NULL);
-        return;
     }
 }
 
@@ -1298,9 +1324,7 @@ static void dbAlias(char *name, char *alias)
                     alias, name);
         yyerror(NULL);
     }
-    else if (dbCreateAlias(pdbEntry, alias)) {
-        fprintf(stderr, "Can't create alias \"%s\" referring to \"%s\"\n",
-                    alias, name);
+    else if (createAlias(pdbEntry, alias) != 0) {
         yyerror(NULL);
     }
     dbFinishEntry(pdbEntry);

modules/database/test/ioc/db/Makefile

@@ -36,6 +36,7 @@ dbTestIoc_DBD += xLink.dbd
 dbTestIoc_DBD += devx.dbd
 dbTestIoc_DBD += jlinkz.dbd
 dbTestIoc_DBD += dbLinkdset.dbd
+dbTestIoc_DBD += dbCore.dbd
 TESTFILES += $(COMMON_DIR)/dbTestIoc.dbd ../xRecord.db
 
 testHarness_SRCS += dbTestIoc_registerRecordDeviceDriver.cpp
@@ -183,6 +184,11 @@ testHarness_SRCS += dbStaticTest.c
 TESTFILES += ../dbStaticTest.db
 TESTFILES += ../dbStaticTestAlias1.db
 TESTFILES += ../dbStaticTestAlias2.db
+TESTFILES += ../dbStaticTestAliasAgain1.db
+TESTFILES += ../dbStaticTestAliasAgain2.db
+TESTFILES += ../dbStaticTestAliasAgain3.db
+TESTFILES += ../dbStaticTestAliasAgainError1.db
+TESTFILES += ../dbStaticTestAliasAgainError2.db
 TESTFILES += ../dbStaticTestRemove.db
 TESTS += dbStaticTest
 

modules/database/test/ioc/db/dbStaticTest.c

@@ -14,6 +14,7 @@
 #include <dbUnitTest.h>
 #include <testMain.h>
 #include <epicsString.h>
+#include <iocsh.h>
 
 
 static void testEntryRemoved(const char *pv)
@@ -321,16 +322,19 @@ static void testDbVerify(const char *record)
     dbFinishEntry(&entry);
 }
 
-static void testWrongAliasRecord(const char *filename)
+static void testReadDatabase(const char *filename, int expectToFail)
 {
     FILE *fp = NULL;
+    long status;
     dbPath(pdbbase,"." OSI_PATH_LIST_SEPARATOR "..");
     dbOpenFile(pdbbase, filename, &fp);
     if(!fp) {
-        testAbort("Unable to read %s", filename);
+        testAbort("Unable to open %s", filename);
     }
-    testOk(dbReadDatabaseFP(&pdbbase, fp, NULL, NULL) != 0,
-           "Wrong alias record in %s is expected to fail", filename);
+    status = dbReadDatabaseFP(&pdbbase, fp, NULL, NULL);
+    testOk(!status == !expectToFail,
+            "Reading %s%s", filename,
+            expectToFail ? " is expected to fail" : "");
 }
 
 void dbTestIoc_registerRecordDeviceDriver(struct dbBase *);
@@ -341,7 +345,7 @@ MAIN(dbStaticTest)
     char *ldirDup;
     FILE *fp = NULL;
 
-    testPlan(340);
+    testPlan(350);
     testdbPrepare();
 
     testdbReadDatabase("dbTestIoc.dbd", NULL, NULL);
@@ -370,8 +374,21 @@ MAIN(dbStaticTest)
     }
     free(ldirDup);
 
-    testWrongAliasRecord("dbStaticTestAlias1.db");
-    testWrongAliasRecord("dbStaticTestAlias2.db");
+    testReadDatabase("dbStaticTestAlias1.db", 1);
+    testReadDatabase("dbStaticTestAlias2.db", 1);
+
+    /* Test re-defining aliases */
+    testReadDatabase("dbStaticTestAliasAgain1.db", 0);
+    testReadDatabase("dbStaticTestAliasAgain1.db", 0);
+    testReadDatabase("dbStaticTestAliasAgain2.db", 0);
+    testReadDatabase("dbStaticTestAliasAgain2.db", 0);
+    testReadDatabase("dbStaticTestAliasAgain3.db", 0);
+    testReadDatabase("dbStaticTestAliasAgain3.db", 0);
+    testReadDatabase("dbStaticTestAliasAgainError1.db", 1);
+    testReadDatabase("dbStaticTestAliasAgainError2.db", 1);
+    iocshCmd("var dbRecordsOnceOnly 1");
+    testReadDatabase("dbStaticTestAliasAgain2.db", 1);
+    testReadDatabase("dbStaticTestAliasAgain3.db", 1);
 
     testEntry("testrec.VAL");
     testEntry("testalias.VAL");

modules/database/test/ioc/db/dbStaticTestAliasAgain1.db

@@ -0,0 +1,4 @@
+# Test re-load alias in record
+record(x, "testrecAgain") {
+    alias("testaliasAgain1")
+}

modules/database/test/ioc/db/dbStaticTestAliasAgain2.db

@@ -0,0 +1,2 @@
+# Test re-load alias for record
+alias("testrecAgain", "testaliasAgain2")

modules/database/test/ioc/db/dbStaticTestAliasAgain3.db

@@ -0,0 +1,2 @@
+# Test re-load alias for alias
+alias("testaliasAgain2", "testaliasAgain3")

modules/database/test/ioc/db/dbStaticTestAliasAgainError1.db

@@ -0,0 +1,2 @@
+# ERROR: alias using name of exising alias for different record
+alias("testrec", "testaliasAgain1")

modules/database/test/ioc/db/dbStaticTestAliasAgainError2.db

@@ -0,0 +1,2 @@
+# ERROR: alias using name of exising record fails
+alias("testrecAgain", "testrec")