Introduce minimal C99 usage to verify compiler support.

This just converts a few for loops in postgres.c to declare variables
in the loop initializer, and uses designated initializers in smgr.c's
definition of smgr callbacks.

Author: Andres Freund
Discussion: https://postgr.es/m/97d4b165-192d-3605-749c-f614a0c4e783@2ndquadrant.com

src/backend/storage/smgr/smgr.c

@@ -67,9 +67,24 @@ typedef struct f_smgr
 
 static const f_smgr smgrsw[] = {
 	/* magnetic disk */
-	{mdinit, NULL, mdclose, mdcreate, mdexists, mdunlink, mdextend,
-		mdprefetch, mdread, mdwrite, mdwriteback, mdnblocks, mdtruncate,
-		mdimmedsync, mdpreckpt, mdsync, mdpostckpt
+	{
+		.smgr_init = mdinit,
+		.smgr_shutdown = NULL,
+		.smgr_close = mdclose,
+		.smgr_create = mdcreate,
+		.smgr_exists = mdexists,
+		.smgr_unlink = mdunlink,
+		.smgr_extend = mdextend,
+		.smgr_prefetch = mdprefetch,
+		.smgr_read = mdread,
+		.smgr_write = mdwrite,
+		.smgr_writeback = mdwriteback,
+		.smgr_nblocks = mdnblocks,
+		.smgr_truncate = mdtruncate,
+		.smgr_immedsync = mdimmedsync,
+		.smgr_pre_ckpt = mdpreckpt,
+		.smgr_sync = mdsync,
+		.smgr_post_ckpt = mdpostckpt
 	}
 };
 

src/backend/tcop/postgres.c

@@ -1310,7 +1310,6 @@ exec_parse_message(const char *query_string,	/* string to execute */
 	{
 		Query	   *query;
 		bool		snapshot_set = false;
-		int			i;
 
 		raw_parse_tree = linitial_node(RawStmt, parsetree_list);
 
@@ -1366,7 +1365,7 @@ exec_parse_message(const char *query_string,	/* string to execute */
 		/*
 		 * Check all parameter types got determined.
 		 */
-		for (i = 0; i < numParams; i++)
+		for (int i = 0; i < numParams; i++)
 		{
 			Oid			ptype = paramTypes[i];
 
@@ -1555,10 +1554,8 @@ exec_bind_message(StringInfo input_message)
 	numPFormats = pq_getmsgint(input_message, 2);
 	if (numPFormats > 0)
 	{
-		int			i;
-
 		pformats = (int16 *) palloc(numPFormats * sizeof(int16));
-		for (i = 0; i < numPFormats; i++)
+		for (int i = 0; i < numPFormats; i++)
 			pformats[i] = pq_getmsgint(input_message, 2);
 	}
 
@@ -1641,8 +1638,6 @@ exec_bind_message(StringInfo input_message)
 	 */
 	if (numParams > 0)
 	{
-		int			paramno;
-
 		params = (ParamListInfo) palloc(offsetof(ParamListInfoData, params) +
 										numParams * sizeof(ParamExternData));
 		/* we have static list of params, so no hooks needed */
@@ -1654,7 +1649,7 @@ exec_bind_message(StringInfo input_message)
 		params->parserSetupArg = NULL;
 		params->numParams = numParams;
 
-		for (paramno = 0; paramno < numParams; paramno++)
+		for (int paramno = 0; paramno < numParams; paramno++)
 		{
 			Oid			ptype = psrc->param_types[paramno];
 			int32		plength;
@@ -1782,10 +1777,8 @@ exec_bind_message(StringInfo input_message)
 	numRFormats = pq_getmsgint(input_message, 2);
 	if (numRFormats > 0)
 	{
-		int			i;
-
 		rformats = (int16 *) palloc(numRFormats * sizeof(int16));
-		for (i = 0; i < numRFormats; i++)
+		for (int i = 0; i < numRFormats; i++)
 			rformats[i] = pq_getmsgint(input_message, 2);
 	}
 
@@ -2212,7 +2205,6 @@ errdetail_params(ParamListInfo params)
 	{
 		StringInfoData param_str;
 		MemoryContext oldcontext;
-		int			paramno;
 
 		/* This code doesn't support dynamic param lists */
 		Assert(params->paramFetch == NULL);
@@ -2222,7 +2214,7 @@ errdetail_params(ParamListInfo params)
 
 		initStringInfo(&param_str);
 
-		for (paramno = 0; paramno < params->numParams; paramno++)
+		for (int paramno = 0; paramno < params->numParams; paramno++)
 		{
 			ParamExternData *prm = &params->params[paramno];
 			Oid			typoutput;
@@ -2325,7 +2317,6 @@ static void
 exec_describe_statement_message(const char *stmt_name)
 {
 	CachedPlanSource *psrc;
-	int			i;
 
 	/*
 	 * Start up a transaction command. (Note that this will normally change
@@ -2384,7 +2375,7 @@ exec_describe_statement_message(const char *stmt_name)
 														 * message type */
 	pq_sendint16(&row_description_buf, psrc->num_params);
 
-	for (i = 0; i < psrc->num_params; i++)
+	for (int i = 0; i < psrc->num_params; i++)
 	{
 		Oid			ptype = psrc->param_types[i];
 
@@ -4179,10 +4170,8 @@ PostgresMain(int argc, char *argv[],
 					numParams = pq_getmsgint(&input_message, 2);
 					if (numParams > 0)
 					{
-						int			i;
-
 						paramTypes = (Oid *) palloc(numParams * sizeof(Oid));
-						for (i = 0; i < numParams; i++)
+						for (int i = 0; i < numParams; i++)
 							paramTypes[i] = pq_getmsgint(&input_message, 4);
 					}
 					pq_getmsgend(&input_message);