Date: Tue, 13 Mar 2018 12:32:17 +0000 From: David Laight <David.Laight@...LAB.COM> To: 'Daniel Micay' <danielmicay@...il.com>, Arend van Spriel <arend.vanspriel@...adcom.com> CC: Andreas Christoforou <andreaschristofo@...il.com>, Kees Cook <keescook@...omium.org>, Kernel Hardening <kernel-hardening@...ts.openwall.com>, QCA ath9k Development <ath9k-devel@....qualcomm.com>, Kalle Valo <kvalo@...eaurora.org>, "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>, Netdev <netdev@...r.kernel.org>, kernel list <linux-kernel@...r.kernel.org> Subject: RE: [PATCH] drivers: net: wireless: ath: ath9: dfs: remove VLA usage From: Daniel Micay > Sent: 10 March 2018 23:45 > > > Just wondering. Is this actually a VLA. FFT_NUM_SAMPLES was static const so > > not really going to show a lot of variation. This array will always have the > > same size on the stack. > > The issue is that unlike in C++, a `static const` can't be used in a > constant expression in C. It's unclear why C is defined that way but > it's how it is and there isn't currently a GCC extension making more > things into constant expressions like C++. 'static' and 'const' are both just qualifiers to a 'variable' You can still take it's address. The language allows you to cast away the 'const' and write to the variable - the effect is probably 'implementation defined'. It is probably required to be valid for 'static const' items to be patchable. David
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