From: "Daniel P. Berrangé" <berrange@redhat.com>
To: Richard Henderson <richard.henderson@linaro.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>, qemu-devel@nongnu.org
Subject: Re: [PATCH 05/26] configure, meson: convert pam detection to meson
Date: Wed, 9 Jun 2021 16:57:16 +0100 [thread overview]
Message-ID: <YMDkOv/bkV5cWLp2@redhat.com> (raw)
In-Reply-To: <c5386a2c-a3b4-0354-5cde-dcbecc587ca9@linaro.org>
On Wed, Jun 09, 2021 at 08:46:22AM -0700, Richard Henderson wrote:
> On 6/8/21 1:20 PM, Daniel P. Berrangé wrote:
> > On Tue, Jun 08, 2021 at 12:45:51PM -0700, Richard Henderson wrote:
> > > On 6/8/21 4:22 AM, Paolo Bonzini wrote:
> > > > +pam = not_found
> > > > +if not get_option('auth_pam').auto() or have_system
> > > > + pam = cc.find_library('pam', has_headers: ['security/pam_appl.h'],
> > >
> > > The condition doesn't look right.
> > > Why are we looking for pam if --disable-pam-auth?
> > >
> > > Surely
> > >
> > > if not get_option('auth_pam').disabled() and have_system
> >
> > This isn't entirely obvious at first glance, but the line after
> > the one you quote with the 'required' param makes it "do the
> > right thing (tm)".
> >
> > The 'auth_pam' option is a tri-state taking 'enabled', 'disabled'
> > and 'auto', with 'auto' being the default state. When a tri-state
> > value is passed as the value of the 'required' parameter, then
> >
> > required==enabled is interpreted as 'required=true'
> > required==auto is interpreted as 'required=false'
> > required==disabled means the entire call is a no-op
> >
> > So this logic:
> >
> > if not get_option('auth_pam').auto() or have_system
> > pam = cc.find_library('pam', has_headers: ['security/pam_appl.h'],
> > required: get_option('auth_pam'),
> > ...)
> >
> > Means
> >
> > => If 'auto' is set, then only look for the library if we're
> > building system emulators. In this case 'required:' will
> > evaluate to 'false', and so we'll gracefully degrade
> > if the library is missing.
>
> If not have_system, there's no point in looking for pam *at all* regardless
> of get_option().
In theory we can simplify to
if have_system
pam = cc.find_library('pam', has_headers: ['security/pam_appl.h'],
required: get_option('auth_pam'),
...)
and this will be fine for builds with system emulators. The only
caveat is that if someone disables system emulators while also
passing -Dpam=enabled, we won't check for pam. That is a
nonsense combination of course, so probably doesn't matter
>
> > => If 'disabled' is set, then the 'find_library' call
> > will not look for anything, immediately return a
> > 'not found' result and let the caller carry on.
>
> This is not true. If 'required: false', find_library *will* look for the
> library, but it will allow it to be missing.
feature==disabled does not map to required: false
https://mesonbuild.com/Build-options.html#features
[quote]
enabled is the same as passing required : true.
auto is the same as passing required : false.
disabled do not look for the dependency and always return 'not-found'.
[/quote]
Regards,
Daniel
--
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next prev parent reply other threads:[~2021-06-09 16:07 UTC|newest]
Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-08 11:22 [PATCH 00/22] Convert more checks to Meson Paolo Bonzini
2021-06-08 11:22 ` [PATCH 01/26] meson: drop unused CONFIG_GCRYPT_HMAC Paolo Bonzini
2021-06-08 17:37 ` Richard Henderson
2021-06-15 13:53 ` Daniel P. Berrangé
2021-06-08 11:22 ` [PATCH 02/26] configure: drop unused variables for xts Paolo Bonzini
2021-06-08 12:15 ` Philippe Mathieu-Daudé
2021-06-08 17:38 ` Richard Henderson
2021-06-15 13:55 ` Daniel P. Berrangé
2021-06-08 11:22 ` [PATCH 03/26] configure, meson: convert crypto detection to meson Paolo Bonzini
2021-06-08 19:16 ` Richard Henderson
2021-06-15 14:01 ` Daniel P. Berrangé
2021-06-08 11:22 ` [PATCH 04/26] configure, meson: convert libtasn1 " Paolo Bonzini
2021-06-08 19:32 ` Richard Henderson
2021-06-15 14:04 ` Daniel P. Berrangé
2021-06-08 11:22 ` [PATCH 05/26] configure, meson: convert pam " Paolo Bonzini
2021-06-08 19:45 ` Richard Henderson
2021-06-08 19:47 ` Richard Henderson
2021-06-08 20:20 ` Daniel P. Berrangé
2021-06-09 15:46 ` Richard Henderson
2021-06-09 15:57 ` Daniel P. Berrangé [this message]
2021-06-09 16:47 ` Richard Henderson
2021-06-15 13:58 ` Paolo Bonzini
2021-06-15 14:05 ` Daniel P. Berrangé
2021-06-08 11:22 ` [PATCH 06/26] configure, meson: convert libusb " Paolo Bonzini
2021-06-15 14:06 ` Daniel P. Berrangé
2021-06-08 11:22 ` [PATCH 07/26] configure, meson: convert libcacard " Paolo Bonzini
2021-06-15 14:08 ` Daniel P. Berrangé
2021-06-08 11:22 ` [PATCH 08/26] configure, meson: convert libusbredir " Paolo Bonzini
2021-06-15 14:09 ` Daniel P. Berrangé
2021-06-08 11:22 ` [PATCH 09/26] configure, meson: convert vte " Paolo Bonzini
2021-06-15 14:24 ` Daniel P. Berrangé
2021-06-15 15:12 ` Paolo Bonzini
2021-06-08 11:22 ` [PATCH 10/26] configure, meson: convert virgl " Paolo Bonzini
2021-06-15 14:25 ` Daniel P. Berrangé
2021-06-08 11:22 ` [PATCH 11/26] configure, meson: convert libdaxctl " Paolo Bonzini
2021-06-15 14:37 ` Daniel P. Berrangé
2021-06-08 11:22 ` [PATCH 12/26] configure, meson: convert libpmem " Paolo Bonzini
2021-06-15 14:37 ` Daniel P. Berrangé
2021-06-08 11:22 ` [PATCH 13/26] configure, meson: convert liburing " Paolo Bonzini
2021-06-15 14:38 ` Daniel P. Berrangé
2021-06-08 11:22 ` [PATCH 14/26] configure, meson: convert libxml2 " Paolo Bonzini
2021-06-15 14:44 ` Daniel P. Berrangé
2021-06-08 11:22 ` [PATCH 15/26] meson: sort header tests Paolo Bonzini
2021-06-08 12:15 ` Philippe Mathieu-Daudé
2021-06-15 14:47 ` Daniel P. Berrangé
2021-06-15 15:16 ` Paolo Bonzini
2021-06-15 15:50 ` Daniel P. Berrangé
2021-06-08 11:22 ` [PATCH 16/26] meson: remove preadv from summary Paolo Bonzini
2021-06-15 14:48 ` Daniel P. Berrangé
2021-06-08 11:22 ` [PATCH 17/26] configure, meson: move CONFIG_IVSHMEM to meson Paolo Bonzini
2021-06-15 14:50 ` Daniel P. Berrangé
2021-06-08 11:22 ` [PATCH 18/26] configure: convert HAVE_BROKEN_SIZE_MAX " Paolo Bonzini
2021-06-15 14:51 ` Daniel P. Berrangé
2021-06-08 11:22 ` [PATCH 19/26] configure: convert compiler tests to meson, part 1 Paolo Bonzini
2021-06-15 14:59 ` Daniel P. Berrangé
2021-06-15 15:15 ` Paolo Bonzini
2021-06-08 11:22 ` [PATCH 20/26] meson: store dependency('threads') in a variable Paolo Bonzini
2021-06-15 15:02 ` Daniel P. Berrangé
2021-06-08 11:22 ` [PATCH 21/26] configure: convert compiler tests to meson, part 2 Paolo Bonzini
2021-06-15 15:03 ` Daniel P. Berrangé
2021-06-08 11:22 ` [PATCH 22/26] configure: convert compiler tests to meson, part 3 Paolo Bonzini
2021-06-15 15:08 ` Daniel P. Berrangé
2021-06-08 11:22 ` [PATCH 23/26] configure: convert CONFIG_STATIC_ASSERT tests to meson Paolo Bonzini
2021-06-08 12:17 ` Philippe Mathieu-Daudé
2021-06-15 15:08 ` Daniel P. Berrangé
2021-06-08 11:22 ` [PATCH 24/26] configure: convert compiler tests to meson, part 4 Paolo Bonzini
2021-06-15 15:13 ` Daniel P. Berrangé
2021-06-08 11:23 ` [PATCH 25/26] configure: convert compiler tests to meson, part 5 Paolo Bonzini
2021-06-15 15:15 ` Daniel P. Berrangé
2021-06-08 11:23 ` [PATCH 26/26] configure: convert compiler tests to meson, part 6 Paolo Bonzini
2021-06-15 15:17 ` Daniel P. Berrangé
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