Repair various defects in dc21234005.

pg_combinebackup had various problems:

* strncpy was used in various places where strlcpy should be used
  instead, to avoid any possibility of the result not being
  \0-terminated.
* scan_for_existing_tablespaces() failed to close the directory,
  and an error when opening the directory was reported with the
  wrong pathname.
* write_reconstructed_file() contained some redundant and therefore
  dead code.
* flush_manifest() didn't check the result of pg_checksum_update()
  as we do in other places, and misused a local pathname variable
  that shouldn't exist at all.

In pg_basebackup, the wrong variable name was used in one place,
due to a copy and paste that was not properly adjusted.

In blkreftable.c, the loop incorrectly doubled chunkno instead of
max_chunks. Fix that. Also remove a nearby assertion per repeated
off-list complaints from Tom Lane.

Per Coverity and subsequent code inspection by me and by Tom Lane.

Discussion: http://postgr.es/m/CA+Tgmobvqqj-DW9F7uUzT-cQqs6wcVb-Xhs=w=hzJnXSE-kRGw@mail.gmail.com

src/bin/pg_basebackup/pg_basebackup.c

@@ -709,7 +709,7 @@ StartLogStreamer(char *startpos, uint32 timeline, char *sysidentifier,
 					 PQserverVersion(conn) < MINIMUM_VERSION_FOR_PG_WAL ?
 					 "pg_xlog" : "pg_wal");
 
-			if (pg_mkdir_p(statusdir, pg_dir_create_mode) != 0 &&
+			if (pg_mkdir_p(summarydir, pg_dir_create_mode) != 0 &&
 				errno != EEXIST)
 				pg_fatal("could not create directory \"%s\": %m", summarydir);
 		}

src/bin/pg_combinebackup/pg_combinebackup.c

@@ -773,8 +773,8 @@ process_directory_recursively(Oid tsoid,
 	 */
 	if (relative_path == NULL)
 	{
-		strncpy(ifulldir, input_directory, MAXPGPATH);
-		strncpy(ofulldir, output_directory, MAXPGPATH);
+		strlcpy(ifulldir, input_directory, MAXPGPATH);
+		strlcpy(ofulldir, output_directory, MAXPGPATH);
 		if (OidIsValid(tsoid))
 			snprintf(manifest_prefix, MAXPGPATH, "pg_tblspc/%u/", tsoid);
 		else
@@ -855,7 +855,7 @@ process_directory_recursively(Oid tsoid,
 
 			/* Append new pathname component to relative path. */
 			if (relative_path == NULL)
-				strncpy(new_relative_path, de->d_name, MAXPGPATH);
+				strlcpy(new_relative_path, de->d_name, MAXPGPATH);
 			else
 				snprintf(new_relative_path, MAXPGPATH, "%s/%s", relative_path,
 						 de->d_name);
@@ -1131,7 +1131,7 @@ scan_for_existing_tablespaces(char *pathname, cb_options *opt)
 	pg_log_debug("scanning \"%s\"", pg_tblspc);
 
 	if ((dir = opendir(pg_tblspc)) == NULL)
-		pg_fatal("could not open directory \"%s\": %m", pathname);
+		pg_fatal("could not open directory \"%s\": %m", pg_tblspc);
 
 	while (errno = 0, (de = readdir(dir)) != NULL)
 	{
@@ -1203,8 +1203,8 @@ scan_for_existing_tablespaces(char *pathname, cb_options *opt)
 			{
 				if (strcmp(tsmap->old_dir, link_target) == 0)
 				{
-					strncpy(ts->old_dir, tsmap->old_dir, MAXPGPATH);
-					strncpy(ts->new_dir, tsmap->new_dir, MAXPGPATH);
+					strlcpy(ts->old_dir, tsmap->old_dir, MAXPGPATH);
+					strlcpy(ts->new_dir, tsmap->new_dir, MAXPGPATH);
 					ts->in_place = false;
 					break;
 				}
@@ -1238,6 +1238,9 @@ scan_for_existing_tablespaces(char *pathname, cb_options *opt)
 		tslist = ts;
 	}
 
+	if (closedir(dir) != 0)
+		pg_fatal("could not close directory \"%s\": %m", pg_tblspc);
+
 	return tslist;
 }
 

src/bin/pg_combinebackup/reconstruct.c

@@ -577,13 +577,12 @@ write_reconstructed_file(char *input_filename,
 			{
 				if (current_block == start_of_range)
 					appendStringInfo(&debug_buf, " %u:%s@" UINT64_FORMAT,
-									 current_block,
-									 s == NULL ? "ZERO" : s->filename,
+									 current_block, s->filename,
 									 (uint64) offsetmap[current_block]);
 				else
 					appendStringInfo(&debug_buf, " %u-%u:%s@" UINT64_FORMAT,
 									 start_of_range, current_block,
-									 s == NULL ? "ZERO" : s->filename,
+									 s->filename,
 									 (uint64) offsetmap[current_block]);
 			}
 

src/bin/pg_combinebackup/write_manifest.c

@@ -241,8 +241,6 @@ escape_json(StringInfo buf, const char *str)
 static void
 flush_manifest(manifest_writer *mwriter)
 {
-	char		pathname[MAXPGPATH];
-
 	if (mwriter->fd == -1 &&
 		(mwriter->fd = open(mwriter->pathname,
 							O_WRONLY | O_CREAT | O_EXCL | PG_BINARY,
@@ -260,13 +258,15 @@ flush_manifest(manifest_writer *mwriter)
 				pg_fatal("could not write \"%s\": %m", mwriter->pathname);
 			else
 				pg_fatal("could not write file \"%s\": wrote only %d of %d bytes",
-						 pathname, (int) wb, mwriter->buf.len);
+						 mwriter->pathname, (int) wb, mwriter->buf.len);
 		}
 
-		if (mwriter->still_checksumming)
+		if (mwriter->still_checksumming &&
 			pg_checksum_update(&mwriter->manifest_ctx,
 							   (uint8 *) mwriter->buf.data,
-							   mwriter->buf.len);
+							   mwriter->buf.len) < 0)
+			pg_fatal("could not update checksum of file \"%s\"",
+					 mwriter->pathname);
 		resetStringInfo(&mwriter->buf);
 	}
 }

src/common/blkreftable.c

@@ -988,8 +988,7 @@ BlockRefTableEntryMarkBlockModified(BlockRefTableEntry *entry,
 		 */
 		max_chunks = Max(16, entry->nchunks);
 		while (max_chunks < chunkno + 1)
-			chunkno *= 2;
-		Assert(max_chunks > chunkno);
+			max_chunks *= 2;
 		extra_chunks = max_chunks - entry->nchunks;
 
 		if (entry->nchunks == 0)