Fix some memory leaks associated with parsing json and manifests

Coverity complained about not freeing some memory associated with
incrementally parsing backup manifests. To fix that, provide and use a new
shutdown function for the JsonManifestParseIncrementalState object, in
line with a suggestion from Tom Lane.

While analysing the problem, I noticed a buglet in freeing memory for
incremental json lexers. To fix that remove a bogus condition on
freeing the memory allocated for them.

src/backend/backup/basebackup_incremental.c

@@ -241,6 +241,9 @@ FinalizeIncrementalManifest(IncrementalBackupInfo *ib)
 	pfree(ib->buf.data);
 	ib->buf.data = NULL;
 
+	/* Done with inc_state, so release that memory too */
+	json_parse_manifest_incremental_shutdown(ib->inc_state);
+
 	/* Switch back to previous memory context. */
 	MemoryContextSwitchTo(oldcontext);
 }

src/bin/pg_combinebackup/load_manifest.c

@@ -208,6 +208,9 @@ load_backup_manifest(char *backup_directory)
 												  inc_state, buffer, rc, bytes_left == 0);
 		}
 
+		/* Release the incremental state memory */
+		json_parse_manifest_incremental_shutdown(inc_state);
+
 		close(fd);
 	}
 

src/bin/pg_verifybackup/pg_verifybackup.c

@@ -484,6 +484,9 @@ parse_manifest_file(char *manifest_path)
 												  inc_state, buffer, rc, bytes_left == 0);
 		}
 
+		/* Release the incremental state memory */
+		json_parse_manifest_incremental_shutdown(inc_state);
+
 		close(fd);
 	}
 

src/common/jsonapi.c

@@ -488,8 +488,6 @@ freeJsonLexContext(JsonLexContext *lex)
 	if (lex->errormsg)
 		destroyStringInfo(lex->errormsg);
 
-	if (lex->flags & JSONLEX_FREE_STRUCT)
-	{
 	if (lex->incremental)
 	{
 		pfree(lex->inc_state->partial_token.data);
@@ -499,9 +497,10 @@ freeJsonLexContext(JsonLexContext *lex)
 		pfree(lex->pstack->fnull);
 		pfree(lex->pstack);
 	}
+
+	if (lex->flags & JSONLEX_FREE_STRUCT)
 		pfree(lex);
 }
-}
 
 /*
  * pg_parse_json

src/common/parse_manifest.c

@@ -123,7 +123,6 @@ static bool parse_xlogrecptr(XLogRecPtr *result, char *input);
 
 /*
  * Set up for incremental parsing of the manifest.
- *
  */
 
 JsonManifestParseIncrementalState *
@@ -163,6 +162,18 @@ json_parse_manifest_incremental_init(JsonManifestParseContext *context)
 	return incstate;
 }
 
+/*
+ * Free an incremental state object and its contents.
+ */
+void
+json_parse_manifest_incremental_shutdown(JsonManifestParseIncrementalState *incstate)
+{
+	pfree(incstate->sem.semstate);
+	freeJsonLexContext(&(incstate->lex));
+	/* incstate->manifest_ctx has already been freed */
+	pfree(incstate);
+}
+
 /*
  * parse the manifest in pieces.
  *

src/include/common/parse_manifest.h

@@ -53,5 +53,6 @@ extern JsonManifestParseIncrementalState *json_parse_manifest_incremental_init(J
 extern void json_parse_manifest_incremental_chunk(
 												  JsonManifestParseIncrementalState *incstate, char *chunk, int size,
 												  bool is_last);
+extern void json_parse_manifest_incremental_shutdown(JsonManifestParseIncrementalState *incstate);
 
 #endif