[v1] misc: Remove variable-length arrays on the stack

[PATCH 04/23] chardev/baum: Avoid dynamic stack allocation

Posted by Philippe Mathieu-Daudé 4 years, 7 months ago

Use autofree heap allocation instead of variable-length
array on the stack.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 chardev/baum.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/chardev/baum.c b/chardev/baum.c
index 0822e9ed5f3..bc09cda3471 100644
--- a/chardev/baum.c
+++ b/chardev/baum.c
@@ -299,7 +299,8 @@ static void baum_chr_accept_input(struct Chardev *chr)
 static void baum_write_packet(BaumChardev *baum, const uint8_t *buf, int len)
 {
     Chardev *chr = CHARDEV(baum);
-    uint8_t io_buf[1 + 2 * len], *cur = io_buf;
+    g_autofree uint8_t *io_buf = g_malloc(1 + 2 * len);
+    uint8_t *cur = io_buf;
     int room;
     *cur++ = ESC;
     while (len--)
-- 
2.26.3

Re: [PATCH 04/23] chardev/baum: Avoid dynamic stack allocation

Posted by Samuel Thibault 4 years, 7 months ago

Philippe Mathieu-Daudé, le mer. 05 mai 2021 23:10:28 +0200, a ecrit:
> Use autofree heap allocation instead of variable-length
> array on the stack.
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>

Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>

> ---
>  chardev/baum.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/chardev/baum.c b/chardev/baum.c
> index 0822e9ed5f3..bc09cda3471 100644
> --- a/chardev/baum.c
> +++ b/chardev/baum.c
> @@ -299,7 +299,8 @@ static void baum_chr_accept_input(struct Chardev *chr)
>  static void baum_write_packet(BaumChardev *baum, const uint8_t *buf, int len)
>  {
>      Chardev *chr = CHARDEV(baum);
> -    uint8_t io_buf[1 + 2 * len], *cur = io_buf;
> +    g_autofree uint8_t *io_buf = g_malloc(1 + 2 * len);
> +    uint8_t *cur = io_buf;
>      int room;
>      *cur++ = ESC;
>      while (len--)
> -- 
> 2.26.3
>

Re: [PATCH 04/23] chardev/baum: Avoid dynamic stack allocation

Posted by Marc-André Lureau 4 years, 7 months ago

On Thu, May 6, 2021 at 1:15 AM Philippe Mathieu-Daudé <philmd@redhat.com>
wrote:

> Use autofree heap allocation instead of variable-length
> array on the stack.
>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>

---
>  chardev/baum.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/chardev/baum.c b/chardev/baum.c
> index 0822e9ed5f3..bc09cda3471 100644
> --- a/chardev/baum.c
> +++ b/chardev/baum.c
> @@ -299,7 +299,8 @@ static void baum_chr_accept_input(struct Chardev *chr)
>  static void baum_write_packet(BaumChardev *baum, const uint8_t *buf, int
> len)
>  {
>      Chardev *chr = CHARDEV(baum);
> -    uint8_t io_buf[1 + 2 * len], *cur = io_buf;
> +    g_autofree uint8_t *io_buf = g_malloc(1 + 2 * len);
>

fwiw, for non-bottleneck code, I would simply use g_malloc0() everywhere,
ymmv

+    uint8_t *cur = io_buf;
>      int room;
>      *cur++ = ESC;
>      while (len--)
> --
> 2.26.3
>
>
>

-- 
Marc-André Lureau