Re: [PATCH] video: fbdev: via_aux_vt1632: remove VLA usage
From: Emil Velikov <hidden>
Date: 2018-03-08 11:58:54
Also in:
dri-devel, lkml
Hi Gustavo, On 7 March 2018 at 19:54, Gustavo A. R. Silva [off-list ref] wrote:
In preparation to enabling -Wvla, remove VLA and replace it with a fixed-length array instead. Also, remove variable 'len'.
What is the reason behind adding -Wvla? Is there a thread some that I can read up on?
quoted hunk ↗ jump to hunk
Notice that no new IDs have been added in seven years. Signed-off-by: Gustavo A. R. Silva <redacted> --- drivers/video/fbdev/via/via_aux_vt1632.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)diff --git a/drivers/video/fbdev/via/via_aux_vt1632.c b/drivers/video/fbdev/via/via_aux_vt1632.c index d24f4cd..0cd0d2a 100644 --- a/drivers/video/fbdev/via/via_aux_vt1632.c +++ b/drivers/video/fbdev/via/via_aux_vt1632.c@@ -35,10 +35,10 @@ static void probe(struct via_aux_bus *bus, u8 addr) .addr = addr, .name = name}; /* check vendor id and device id */ - const u8 id[] = {0x06, 0x11, 0x92, 0x31}, len = ARRAY_SIZE(id); - u8 tmp[len]; + const u8 id[4] = {0x06, 0x11, 0x92, 0x31}; + u8 tmp[4]; - if (!via_aux_read(&drv, 0x00, tmp, len) || memcmp(id, tmp, len)) + if (!via_aux_read(&drv, 0x00, tmp, 4) || memcmp(id, tmp, 4))
Generally, hard coding a bunch of numbers like that makes for
confusing and fragile code.
A lot simpler and more obvious solution is like the following.
It silences the compiler warning (-Wvla - pedantic) you while keeping
the original clarity.
const u8 id[] = {0x06, 0x11, 0x92, 0x31}, len = ARRAY_SIZE(id);
- u8 tmp[len];
+ u8 tmp[ARRAY_SIZE(id)]; // Using len causes a Wvla warning
HTH
Emil