[PATCH 2/3] backupfile: less-aggressive buffer growth

[Paul Eggert]

* lib/backupfile.c: Include intprops.h.
(numbered_backup): Grow buffer by the usual 50%, not 100%.
This is easier to do now that we have xalloc_count_t.
* modules/backup-rename, modules/backupfile: Depend on intprops.
---
 ChangeLog             | 6 ++++++
 lib/backupfile.c      | 6 ++++--
 modules/backup-rename | 1 +
 modules/backupfile    | 1 +
 4 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 0c3ea48fe..c68da0df8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
 2021-04-06  Paul Eggert  <eggert@cs.ucla.edu>
 
+       backupfile: less-aggressive buffer growth
+       * lib/backupfile.c: Include intprops.h.
+       (numbered_backup): Grow buffer by the usual 50%, not 100%.
+       This is easier to do now that we have xalloc_count_t.
+       * modules/backup-rename, modules/backupfile: Depend on intprops.
+
        xalloc-oversized: export xalloc_count_t
        * lib/xalloc-oversized.h (__xalloc_oversized, xalloc_oversized):
        * lib/xmalloca.h (nmalloca):
diff --git a/lib/backupfile.c b/lib/backupfile.c
index c53e3f335..1e427e8de 100644
--- a/lib/backupfile.c
+++ b/lib/backupfile.c
@@ -34,6 +34,7 @@
 #include "attribute.h"
 #include "basename-lgpl.h"
 #include "idx.h"
+#include "intprops.h"
 #include "opendirat.h"
 #include "renameatu.h"
 #include "xalloc-oversized.h"
@@ -270,8 +271,9 @@ numbered_backup (int dir_fd, char **buffer, size_t 
buffer_size, size_t filelen,
       size_t new_buffer_size = filelen + 2 + versionlenmax + 2;
       if (buffer_size < new_buffer_size)
         {
-          if (! xalloc_oversized (new_buffer_size, 2))
-            new_buffer_size *= 2;
+          xalloc_count_t grown;
+          if (! INT_ADD_WRAPV (new_buffer_size, new_buffer_size >> 1, &grown))
+            new_buffer_size = grown;
           char *new_buf = realloc (buf, new_buffer_size);
           if (!new_buf)
             {
diff --git a/modules/backup-rename b/modules/backup-rename
index 4497b3350..c50e874ff 100644
--- a/modules/backup-rename
+++ b/modules/backup-rename
@@ -17,6 +17,7 @@ closedir
 d-ino
 fcntl-h
 idx
+intprops
 memcmp
 opendirat
 readdir
diff --git a/modules/backupfile b/modules/backupfile
index 41cf99b02..42c8c9ed5 100644
--- a/modules/backupfile
+++ b/modules/backupfile
@@ -17,6 +17,7 @@ closedir
 d-ino
 fcntl-h
 idx
+intprops
 memcmp
 opendirat
 readdir
-- 
2.27.0