Libguestfs - Apr 2017 - [PATCH] daemon: Remove use of fixed-size stack buffers.

GCC 7 complains that the fixed size buffers are not large enough
(at least in theory) when using ‘-O3 -mtune=broadwell’.
---
 daemon/devsparts.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/daemon/devsparts.c b/daemon/devsparts.c
index 584e7d8b8..eac79197e 100644
--- a/daemon/devsparts.c
+++ b/daemon/devsparts.c
@@ -125,13 +125,16 @@ foreach_block_device (block_dev_func_t func, bool
return_md)
 static int
 add_device (const char *device, struct stringsbuf *r)
 {
-  char dev_path[256];
-  snprintf (dev_path, sizeof dev_path, "/dev/%s", device);
+  CLEANUP_FREE char *dev_path;
 
-  if (add_string (r, dev_path) == -1) {
+  if (asprintf (&dev_path, "/dev/%s", device) == -1) {
+    reply_with_perror ("asprintf");
     return -1;
   }
 
+  if (add_string (r, dev_path) == -1)
+    return -1;
+
   return 0;
 }
 
@@ -153,10 +156,13 @@ do_list_devices (void)
 static int
 add_partitions (const char *device, struct stringsbuf *r)
 {
-  char devdir[256];
+  CLEANUP_FREE char *devdir;
 
   /* Open the device's directory under /sys/block */
-  snprintf (devdir, sizeof devdir, "/sys/block/%s", device);
+  if (asprintf (&devdir, "/sys/block/%s", device) == -1) {
+    reply_with_perror ("asprintf");
+    return -1;
+  }
 
   DIR *dir = opendir (devdir);
   if (!dir) {
-- 
2.12.0

On Wednesday, 19 April 2017 18:47:11 CEST Richard W.M. Jones
wrote:
> GCC 7 complains that the fixed size buffers are not large enough
> (at least in theory) when using ‘-O3 -mtune=broadwell’.
> ---
>  daemon/devsparts.c | 16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/daemon/devsparts.c b/daemon/devsparts.c
> index 584e7d8b8..eac79197e 100644
> --- a/daemon/devsparts.c
> +++ b/daemon/devsparts.c
> @@ -125,13 +125,16 @@ foreach_block_device (block_dev_func_t func, bool
return_md)
>  static int
>  add_device (const char *device, struct stringsbuf *r)
>  {
> -  char dev_path[256];
> -  snprintf (dev_path, sizeof dev_path, "/dev/%s", device);
> +  CLEANUP_FREE char *dev_path;
Please init it to NULL, so it is not a problem in case new code is
added between this and what follows.  OTOH ...
>  
> -  if (add_string (r, dev_path) == -1) {
> +  if (asprintf (&dev_path, "/dev/%s", device) == -1) {
> +    reply_with_perror ("asprintf");
>      return -1;
>    }
>  
> +  if (add_string (r, dev_path) == -1)
> +    return -1;
... this could be add_string_nodup, handing over the dev_path string
to the stringbuf, and thus removing one memory allocation.
> +
>    return 0;
>  }
>  
> @@ -153,10 +156,13 @@ do_list_devices (void)
>  static int
>  add_partitions (const char *device, struct stringsbuf *r)
>  {
> -  char devdir[256];
> +  CLEANUP_FREE char *devdir;
Same note here about the initialization to NULL.

Thanks,
-- 
Pino Toscano