[libvirt PATCH 1/6] meson: Allow larger stack frames when instrumenting

[Pavel Hrdina]

On Mon, May 03, 2021 at 12:01:41PM +0200, Tim Wiederhake wrote:
> When enabling sanitizers, gcc adds some instrumentation to the code
> that may enlarge stack frames. Some function's stack frames are already
> close to the limit of 4096 and are enlarged past that threshold,
> e.g. virLXCProcessStart which reaches a frame size of 4624 bytes.
> 
> Signed-off-by: Tim Wiederhake <twiederh at redhat.com>
> ---
>  meson.build | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/meson.build b/meson.build
> index 618cbd6b1d..bbdbe4afd8 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -278,7 +278,8 @@ cc_flags += [
>    '-Wformat-y2k',
>    '-Wformat-zero-length',
>    '-Wframe-address',
> -  '-Wframe-larger-than=4096',
> +  # sanitizer instrumentation may enlarge stack frames
> +  '-Wframe-larger-than=@0@'.format(get_option('b_sanitize') in ['', 'none'] ? 4096 : 8192),
>    '-Wfree-nonheap-object',
>    '-Whsa',
>    '-Wif-not-aligned',

Looks good but needs some polishing. I would do something similar to
what we do with -Walloc-size-larger-than:

    # sanitizer instrumentation may enlarge stack frames
    stack_frame_size = get_option('b_sanitize') == 'none' ? 4096 : 8192

    cc_flags += [
      ...
      '-Wframe-larger-than=@0@'.format(stack_frame_size),
      ...
    ]

In addition there is no need to check for empty string as meson will
handle that while parsing the command argument. All of the following
commands:

    meson build -Db_sanitize=
    meson build -Db_sanitize=""
    meson build -Db_sanitize=" "
    meson build -Db_sanitize="asdf"

result in this error (the value in the error message reflects the one
actually used):

    meson.build:1:0: ERROR: Value "" (of type "string") for combo option "Code sanitizer to use" is not one of the choices. Possible choices are (as string): "none", "address", "thread", "undefined", "memory", "address,undefined".

Pavel
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