gendwarfksyms: order -T symtypes output by name

When writing symtypes information, we iterate through the entire hash
table containing type expansions. The key order varies unpredictably
as new entries are added, making it harder to compare symtypes between
builds.

Resolve this by sorting the type expansions by name before output.

Signed-off-by: Giuliano Procida <gprocida@google.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>

Author: myxoid

scripts/gendwarfksyms/types.c

@@ -6,6 +6,8 @@
 #define _GNU_SOURCE
 #include <inttypes.h>
 #include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
 #include <zlib.h>
 
 #include "gendwarfksyms.h"
@@ -150,20 +152,41 @@ static void type_map_add(const char *name, struct type_expansion *type)
 	}
 }
 
+static int cmp_expansion_name(const void *p1, const void *p2)
+{
+	struct type_expansion *const *e1 = p1;
+	struct type_expansion *const *e2 = p2;
+
+	return strcmp((*e1)->name, (*e2)->name);
+}
+
 static void type_map_write(FILE *file)
 {
 	struct type_expansion *e;
 	struct hlist_node *tmp;
+	struct type_expansion **es;
+	size_t count = 0;
+	size_t i = 0;
 
 	if (!file)
 		return;
 
-	hash_for_each_safe(type_map, e, tmp, hash) {
-		checkp(fputs(e->name, file));
+	hash_for_each_safe(type_map, e, tmp, hash)
+		++count;
+	es = xmalloc(count * sizeof(struct type_expansion *));
+	hash_for_each_safe(type_map, e, tmp, hash)
+		es[i++] = e;
+
+	qsort(es, count, sizeof(struct type_expansion *), cmp_expansion_name);
+
+	for (i = 0; i < count; ++i) {
+		checkp(fputs(es[i]->name, file));
 		checkp(fputs(" ", file));
-		type_list_write(&e->expanded, file);
+		type_list_write(&es[i]->expanded, file);
 		checkp(fputs("\n", file));
 	}
+
+	free(es);
 }
 
 static void type_map_free(void)