printf("%lf") is not portable, so omit the "l".

The "l" (ell) width spec means something in the corresponding scanf usage,
but not here.  While modern POSIX says that applying "l" to "f" and other
floating format specs is a no-op, SUSv2 says it's undefined.  Buildfarm
experience says that some old compilers emit warnings about it, and at
least one old stdio implementation (mingw's "ANSI" option) actually
produces wrong answers and/or crashes.

Discussion: https://postgr.es/m/21670.1526769114@sss.pgh.pa.us
Discussion: https://postgr.es/m/c085e1da-0d64-1c15-242d-c921f32e0d5c@dunslane.net

contrib/pageinspect/btreefuncs.c

@@ -563,7 +563,7 @@ bt_metap(PG_FUNCTION_ARGS)
 	if (metad->btm_version == BTREE_VERSION)
 	{
 		values[j++] = psprintf("%u", metad->btm_oldest_btpo_xact);
-		values[j++] = psprintf("%lf", metad->btm_last_cleanup_num_heap_tuples);
+		values[j++] = psprintf("%f", metad->btm_last_cleanup_num_heap_tuples);
 	}
 	else
 	{

doc/src/sgml/ecpg.sgml

@@ -1678,7 +1678,7 @@ while (1)
     <para>
      Here is an example using the data type <type>complex</type> from
      the example in <xref linkend="xtypes"/>.  The external string
-     representation of that type is <literal>(%lf,%lf)</literal>,
+     representation of that type is <literal>(%f,%f)</literal>,
      which is defined in the
      functions <function>complex_in()</function>
      and <function>complex_out()</function> functions

src/backend/access/rmgrdesc/nbtdesc.c

@@ -100,7 +100,7 @@ btree_desc(StringInfo buf, XLogReaderState *record)
 			{
 				xl_btree_metadata *xlrec = (xl_btree_metadata *) rec;
 
-				appendStringInfo(buf, "oldest_btpo_xact %u; last_cleanup_num_heap_tuples: %lf",
+				appendStringInfo(buf, "oldest_btpo_xact %u; last_cleanup_num_heap_tuples: %f",
 								 xlrec->oldest_btpo_xact,
 								 xlrec->last_cleanup_num_heap_tuples);
 				break;

src/interfaces/ecpg/test/compat_informix/sqlda.pgc

@@ -37,7 +37,7 @@ dump_sqlda(sqlda_t *sqlda)
 			printf("name sqlda descriptor: '%s' value %d\n", sqlda->sqlvar[i].sqlname, *(int *)sqlda->sqlvar[i].sqldata);
 			break;
 		case SQLFLOAT:
-			printf("name sqlda descriptor: '%s' value %lf\n", sqlda->sqlvar[i].sqlname, *(double *)sqlda->sqlvar[i].sqldata);
+			printf("name sqlda descriptor: '%s' value %f\n", sqlda->sqlvar[i].sqlname, *(double *)sqlda->sqlvar[i].sqldata);
 			break;
 		case SQLDECIMAL:
 			{

src/interfaces/ecpg/test/expected/compat_informix-sqlda.c

@@ -142,7 +142,7 @@ dump_sqlda(sqlda_t *sqlda)
 			printf("name sqlda descriptor: '%s' value %d\n", sqlda->sqlvar[i].sqlname, *(int *)sqlda->sqlvar[i].sqldata);
 			break;
 		case SQLFLOAT:
-			printf("name sqlda descriptor: '%s' value %lf\n", sqlda->sqlvar[i].sqlname, *(double *)sqlda->sqlvar[i].sqldata);
+			printf("name sqlda descriptor: '%s' value %f\n", sqlda->sqlvar[i].sqlname, *(double *)sqlda->sqlvar[i].sqldata);
 			break;
 		case SQLDECIMAL:
 			{

src/interfaces/ecpg/test/expected/preproc-outofscope.c

@@ -337,7 +337,7 @@ if (sqlca.sqlcode < 0) exit (1);}
 		get_record1();
 		if (sqlca.sqlcode == ECPG_NOT_FOUND)
 			break;
-		printf("id=%d%s t='%s'%s d1=%lf%s d2=%lf%s c = '%s'%s\n",
+		printf("id=%d%s t='%s'%s d1=%f%s d2=%f%s c = '%s'%s\n",
 			myvar->id, mynullvar->id ? " (NULL)" : "",
 			myvar->t, mynullvar->t ? " (NULL)" : "",
 			myvar->d1, mynullvar->d1 ? " (NULL)" : "",

src/interfaces/ecpg/test/expected/sql-sqlda.c

@@ -158,7 +158,7 @@ dump_sqlda(sqlda_t *sqlda)
 			break;
 #endif
 		case ECPGt_double:
-			printf("name sqlda descriptor: '%s' value %lf\n", sqlda->sqlvar[i].sqlname.data, *(double *)sqlda->sqlvar[i].sqldata);
+			printf("name sqlda descriptor: '%s' value %f\n", sqlda->sqlvar[i].sqlname.data, *(double *)sqlda->sqlvar[i].sqldata);
 			break;
 		case ECPGt_numeric:
 			{

src/interfaces/ecpg/test/preproc/outofscope.pgc

@@ -101,7 +101,7 @@ main (void)
 		get_record1();
 		if (sqlca.sqlcode == ECPG_NOT_FOUND)
 			break;
-		printf("id=%d%s t='%s'%s d1=%lf%s d2=%lf%s c = '%s'%s\n",
+		printf("id=%d%s t='%s'%s d1=%f%s d2=%f%s c = '%s'%s\n",
 			myvar->id, mynullvar->id ? " (NULL)" : "",
 			myvar->t, mynullvar->t ? " (NULL)" : "",
 			myvar->d1, mynullvar->d1 ? " (NULL)" : "",

src/interfaces/ecpg/test/sql/sqlda.pgc

@@ -45,7 +45,7 @@ dump_sqlda(sqlda_t *sqlda)
 			break;
 #endif
 		case ECPGt_double:
-			printf("name sqlda descriptor: '%s' value %lf\n", sqlda->sqlvar[i].sqlname.data, *(double *)sqlda->sqlvar[i].sqldata);
+			printf("name sqlda descriptor: '%s' value %f\n", sqlda->sqlvar[i].sqlname.data, *(double *)sqlda->sqlvar[i].sqldata);
 			break;
 		case ECPGt_numeric:
 			{