Re: [PATCH] block: Use a GString in bdrv_perm_names()

[Philippe Mathieu-Daudé]

On 1/10/20 6:15 PM, Alberto Garcia wrote:
This is a bit more efficient than having to allocate and free memory
for each new permission.
The default size (30) is enough for "consistent read, write, resize".

Signed-off-by: Alberto Garcia <be...@igalia.com>
---
  block.c | 11 ++++++-----
  1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/block.c b/block.c
index 1b6f7c86e8..2bc9e58392 100644
--- a/block.c
+++ b/block.c
@@ -1976,18 +1976,19 @@ char *bdrv_perm_names(uint64_t perm)
          { 0, NULL }
      };
  
-    char *result = g_strdup("");
+    GString *result = g_string_sized_new(30);
      struct perm_name *p;
  
      for (p = permissions; p->name; p++) {
          if (perm & p->perm) {
-            char *old = result;
-            result = g_strdup_printf("%s%s%s", old, *old ? ", " : "", p->name);
-            g_free(old);
+            if (result->len > 0) {
+                g_string_append(result, ", ");
+            }
+            g_string_append(result, p->name);
          }
      }
  
-    return result;
+    return g_string_free(result, FALSE);
  }

Maybe similar cleanup can be done to report_unsupported_feature() in 
block/qcow2.c.