Re: [PATCH] kasan: turn off asan-stack for clang-8 and earlier

[Arnd Bergmann]

On Wed, Feb 20, 2019 at 10:13 PM Arnd Bergmann <arnd@xxxxxxxx> wrote:
>
> In the example in https://bugs.llvm.org/show_bug.cgi?id=38809#c12
> (https://godbolt.org/z/ylsGSQ) there is no inlining, yet clang uses
> over ten times as much stack space as gcc, for reasons I still
> can't explain. My assumption right now is that the underlying bug
> causes most of the problems with excessive stack usage in
> allmodconfig kernels.

Here is an even more minimal example:

struct s { int i[5]; } f(void);
void g(void) { f(); f();}

https://godbolt.org/z/d_KWkh

It's clear that clang does /something/ here when asan-stack=1 is
set, but I fail to see what it is, or why that is necessary.

The output of clang with asan-stack=0 is the expected
code, and basically identical to what gcc produces with or
without asan-stack.

      Arnd