[libcamera-devel] [PATCH v2] meson: Don't set _FORTIFY_SOURCE for ChromeOS
Jacopo Mondi
jacopo.mondi at ideasonboard.com
Thu Sep 14 09:53:15 CEST 2023
Hi George
On Tue, Sep 12, 2023 at 09:06:20AM -0600, George Burgess via libcamera-devel wrote:
> Hey,
>
> > Do you expect to have -D_FORTIFY_SOURCE and -U_FORTIFY_SOURCE in the
> > same command line, so that you have to reset has_fortify_define to
> > false if it was previously been set to true here below ?
>
> You're correct - the code as written intends to answer "will FORTIFY _be
> enabled_ by `cpp_args`?" If you'd like, I'm happy to reduce complexity and have
> the code determine whether `-D_FORTIFY_SOURCE*` was specified at all. Either
> would work equally well for ChromeOS. :)
Please do not mangle the email content and try to reply where the
comment was made in the patch, otherwise it's hard to find context.
I'll copy your reply below.
>
> George
>
> On Tue, Sep 12, 2023 at 7:22 AM Jacopo Mondi
> <jacopo.mondi at ideasonboard.com> wrote:
> >
> > Hi George
> >
> > On Mon, Sep 11, 2023 at 05:09:07PM -0600, George Burgess IV via libcamera-devel wrote:
> > > ChromeOS is moving to a platform default of `_FORTIFY_SOURCE=3`, and
> > > this definition conflicts with that:
> > >
> > > <command line>:4:9: error: '_FORTIFY_SOURCE' macro redefined
> > > [-Werror,-Wmacro-redefined]
> > >
> > > Rather than adding logic to keep up with their local configuration, it
> > > seems best to leave setting _FORTIFY_SOURCE on ChromeOS up to ChromeOS.
> > >
> > > Signed-off-by: George Burgess IV <gbiv at google.com>
> > > ---
> > > meson.build | 24 +++++++++++++++++++-----
> > > 1 file changed, 19 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/meson.build b/meson.build
> > > index 7959b538..2e834263 100644
> > > --- a/meson.build
> > > +++ b/meson.build
> > > @@ -99,12 +99,26 @@ if cc.get_id() == 'clang'
> > > error('clang version is too old, libcamera requires 9.0 or newer')
> > > endif
> > >
> > > - # Turn _FORTIFY_SOURCE by default on optimised builds (as it requires -O1
> > > - # or higher). This is needed on clang only as gcc enables it by default.
> > > + # Turn _FORTIFY_SOURCE by default on. This is needed on clang only as gcc
> > > + # enables it by default. FORTIFY will not work properly with `-O0`, and may
> > > + # result in macro redefinition errors if the user already has a setting for
> > > + # `-D_FORTIFY_SOURCE`. Do not enable FORTIFY in either of those cases.
> > > if get_option('optimization') != '0'
> > > - common_arguments += [
> > > - '-D_FORTIFY_SOURCE=2',
> > > - ]
> > > + has_fortify_define = false
> > > + # Assume that if the user requests a FORTIFY level in cpp_args, they
> > > + # do the same for c_args.
> > > + foreach flag : get_option('cpp_args')
> > > + if flag == '-U_FORTIFY_SOURCE'
> > > + has_fortify_define = false
> >
> > Do you expect to have -D_FORTIFY_SOURCE and -U_FORTIFY_SOURCE in the
> > same command line, so that you have to reset has_fortify_define to
> > false if it was previously been set to true here below ?
> >
> > Otherwise I might be missing why you have to set 'has_fortify_define =
> > false' when the variable is already initialized to 'false'...
> >
>
> You're correct - the code as written intends to answer "will FORTIFY _be
> enabled_ by `cpp_args`?" If you'd like, I'm happy to reduce complexity and have
> the code determine whether `-D_FORTIFY_SOURCE*` was specified at all. Either
> would work equally well for ChromeOS. :)
As I read this the code is written to protect against the case where
-U_FORTIFY_SOURCE is specified in the same command line -after-
-D_FORTIFY_SOURCE, isn't it ?
My comment was about the fact `has_fortify_define` is already
initialized to false, so there is not need for
if flag == '-U_FORTIFY_SOURCE'
has_fortify_define = false
Unless you don't expect the above described case.
As command lines are usually generated by the build system and
multiple options to enable/disable a feature might be concatenated in
the same line, I'm not opposed to this, but I was wondering if this
was by design or not.
> > > + elif flag.startswith('-D_FORTIFY_SOURCE=')
> > > + has_fortify_define = true
> > > + endif
> > > + endforeach
> > > + if not has_fortify_define
> > > + common_arguments += [
> > > + '-D_FORTIFY_SOURCE=2',
> > > + ]
> > > + endif
> > > endif
> > >
> > > # Use libc++ by default if available instead of libstdc++ when compiling
> > > --
> > > 2.42.0.283.g2d96d420d3-goog
> > >
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