Fix for issue #47 - double free of COL_INFO object (#48)

* Fix for issue #47 - double free of COL_INFO object due to refcount
breakage during reuse of directly found object in getColumnsInfo(...).
One more possible memory leak of COL_INFO objects in
getColumnsInfo(...).

Signed-off-by: Alexandr Kuznetsov <progmachine@xenlab.one>

* Fix spelling mistake in comment.

Signed-off-by: Alexandr Kuznetsov <progmachine@xenlab.one>

---------

Signed-off-by: Alexandr Kuznetsov <progmachine@xenlab.one>

Author: progmachine

.gitignore

@@ -36,13 +36,15 @@ windows-local.mak
 /Makefile.in
 /aclocal.m4
 /autom4te.cache/
+/autom4te.cache/*
 /config/
 /config.h
 /config.h.in
 /config.log
 /config.status
 /configure
 /libtool
+/psqlodbca.la
 /psqlodbcw.la
 /stamp-h1
 
@@ -107,6 +109,11 @@ bld/
 [Ll]og/
 [Ll]ogs/
 
+# Eclipse project options
+/.project
+/.cproject
+/.settings
+
 # Visual Studio 2015/2017 cache/options directory
 .vs/
 # Uncomment if you have tasks that create the project's static files in wwwroot

connection.c

@@ -556,6 +556,7 @@ CC_clear_col_info(ConnectionClass *self, BOOL destroy)
 			/* Going through COL_INFO cache table and releasing coli objects. */
 			if (coli = self->col_info[i], NULL != coli)
 			{
+				MYLOG(0, "!!!refcnt %p:%d -> %d\n", coli, coli->refcnt, coli->refcnt - 1);
 				coli->refcnt--;
 				if (coli->refcnt <= 0)
 				{

parse.c

@@ -829,7 +829,7 @@ getColumnsInfo(ConnectionClass *conn, TABLE_INFO *wti, OID greloid, StatementCla
 	{
 		BOOL		coli_exist = FALSE;
 		COL_INFO	*coli = NULL, *ccoli = NULL, *tcoli;
-		int		k;
+		int		 k, tmp_refcnt = 0;
 		time_t		acctime = 0;
 
 		MYLOG(0, "      Success\n");
@@ -882,6 +882,8 @@ getColumnsInfo(ConnectionClass *conn, TABLE_INFO *wti, OID greloid, StatementCla
 		if (coli_exist)
 		{
 			/* We have ready to use coli object. Cleaning it. */
+			tmp_refcnt = coli->refcnt; /* If we found coli with greloid, then some TABLE_INFO objects may have references to it -> save refcnt for them. */
+			tmp_refcnt--; /* Down the road we will increase refcnt again to account for the reference from ConnectionClass object to coli object. */
 			free_col_info_contents(coli);
 		}
 		else
@@ -921,6 +923,7 @@ getColumnsInfo(ConnectionClass *conn, TABLE_INFO *wti, OID greloid, StatementCla
 		}
 		col_info_initialize(coli);
 
+		coli->refcnt = tmp_refcnt;
 		coli->refcnt++; /* Counting one reference to coli object from connection COL_INFO cache table. */
 		coli->result = res;
 		if (res && QR_get_num_cached_tuples(res) > 0)
@@ -976,6 +979,17 @@ MYLOG(DETAIL_LOG_LEVEL, "oid item == %s\n", (const char *) QR_get_value_backend_
 		MYLOG(0, "Created col_info table='%s', ntables=%d\n", PRINT_NAME(wti->table_name), conn->ntables);
 		/* Associate a table from the statement with a SQLColumn info */
 		found = TRUE;
+		if (wti->col_info)
+		{
+			/* wti also has reference to COL_INFO object, so we must release it. */
+MYLOG(0, "!!!refcnt %p:%d -> %d\n", wti->col_info, wti->col_info->refcnt, wti->col_info->refcnt - 1);
+			wti->col_info->refcnt--;
+			if (wti->col_info->refcnt <= 0)
+			{
+				free_col_info_contents(wti->col_info);
+				free(wti->col_info);
+			}
+		}
 		coli->refcnt++; /* Counting another one reference to coli object from TABLE_INFO wti object. */
 		wti->col_info = coli;
 	}