From: "Roberts, William C" <william.c.roberts@intel.com>
To: Stephen Smalley <sds@tycho.nsa.gov>,
Petr Lautrbach <plautrba@redhat.com>,
"selinux@vger.kernel.org" <selinux@vger.kernel.org>
Cc: Ondrej Mosnacek <omosnace@redhat.com>
Subject: RE: gcc 9.0.0 build issues
Date: Fri, 8 Feb 2019 19:40:35 +0000 [thread overview]
Message-ID: <476DC76E7D1DF2438D32BFADF679FC5649CE8B71@ORSMSX101.amr.corp.intel.com> (raw)
In-Reply-To: <3a9f2281-aad4-58fd-ab8e-cb99a8da0fae@tycho.nsa.gov>
> -----Original Message-----
> From: Stephen Smalley [mailto:sds@tycho.nsa.gov]
> Sent: Thursday, February 7, 2019 10:17 AM
> To: Roberts, William C <william.c.roberts@intel.com>; Petr Lautrbach
> <plautrba@redhat.com>; selinux@vger.kernel.org
> Cc: Ondrej Mosnacek <omosnace@redhat.com>
> Subject: Re: gcc 9.0.0 build issues
>
> On 2/7/19 12:52 PM, Roberts, William C wrote:
> >
> >
> >> -----Original Message-----
> >> From: Petr Lautrbach [mailto:plautrba@redhat.com]
> >> Sent: Thursday, February 7, 2019 4:40 AM
> >> To: selinux@vger.kernel.org
> >> Cc: Petr Lautrbach <plautrba@redhat.com>; Roberts, William C
> >> <william.c.roberts@intel.com>; Ondrej Mosnacek <omosnace@redhat.com>
> >> Subject: Re: gcc 9.0.0 build issues
> >>
> >>
> >> Ondrej Mosnacek <omosnace@redhat.com> writes:
> >>
> >>> On Fri, Feb 1, 2019 at 8:36 PM Petr Lautrbach <plautrba@redhat.com>
> >>> wrote:
> >>>> gcc-9.0.0-0.3.fc30.x86_64 from Fedora Rawhide:
> >>>>
> >>>> gcc version 9.0.0 20190119 (Red Hat 9.0.0-0.3) (GCC)
> >>>>
> >> ...
> >>>> When libselinux is built separately, other CFLAGS is used:
> >>>>
> >>>> $ cd libselinux
> >>>>
> >>>> $ make DESTDIR=~/obj install install-pywrap ...
> >>>>
> >>>> make[1]: Entering directory
> >>>> '/home/build/SELinuxProject-selinux/libselinux/src'
> >>>>
> >>>> cc -O -Wall -W -Wundef -Wformat-y2k -Wformat-security -Winit-self
> >>>> -Wmissing-include-dirs -Wunused -Wunknown-pragmas -Wstrict-aliasing
> >>>> -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-align
> >>>> -Wwrite-strings -Waggregate-return -Wstrict-prototypes
> >>>> -Wold-style-definition -Wmissing-prototypes -Wmissing-declarations
> >>>> -Wmissing-noreturn -Wmissing-format-attribute -Wredundant-decls
> >>>> -Wnested-externs -Winline -Winvalid-pch -Wvolatile-register-var
> >>>> -Wdisabled-optimization -Wbuiltin-macro-redefined -Wattributes
> >>>> -Wmultichar -Wdeprecated-declarations -Wdiv-by-zero
> >>>> -Wdouble-promotion -Wendif-labels -Wextra -Wformat-extra-args
> >>>> -Wformat-zero-length -Wformat=2 -Wmultichar -Woverflow
> >>>> -Wpointer-to-int-cast -Wpragmas -Wno-missing-field-initializers
> >>>> -Wno-sign-compare -Wno-format-nonliteral
> >>>> -Wframe-larger-than=32768
> >>>> -fstack-protector-all --param=ssp-buffer-size=4 -fexceptions
> >>>> -fasynchronous-unwind-tables -fdiagnostics-show-option
> >>>> -funit-at-a-time -Werror -Wno-aggregate-return -Wno-redundant-decls
> >>>> -fipa-pure-const -Wlogical-op -Wpacked-bitfield-compat -Wsync-nand
> >>>> -Wcoverage-mismatch -Wcpp -Wformat-contains-nul -Wnormalized=nfc
> >>>> -Wsuggest-attribute=const -Wsuggest-attribute=noreturn
> >>>> -Wsuggest-attribute=pure -Wtrampolines -Wjump-misses-init
> >>>> -Wno-suggest-attribute=pure -Wno-suggest-attribute=const
> >>>> -U_FORTIFY_SOURCE
> >>>> -D_FORTIFY_SOURCE=2
> >>>> -Wstrict-overflow=5 -I../include -D_GNU_SOURCE
> >>>> -DNO_ANDROID_BACKEND -c -o booleans.o booleans.c
> >>>> booleans.c: In function ‘security_get_boolean_names’:
> >>>> booleans.c:39:5: error: assuming signed overflow does not occur
> >>>> when changing X +- C1 cmp C2 to X cmp C2 -+ C1 [-Werror=strict-overflow]
> >>>> 39 | int security_get_boolean_names(char ***names, int *len)
> >>>> | ^~~~~~~~~~~~~~~~~~~~~~~~~~
> >>>> cc1: all warnings being treated as errors
> >>>
> >>> This one is really weird... Perhaps a bug in GCC? At the very least
> >>> the warning message and source code location are super confusing,
> >>> which is a bug on its own...
> >>
> >> It's detected only with -Wstrict-overflow=3 and higher. Makefile in
> >> libselinux uses level 5 which was added by commit
> >> 9fe430345 ("Makefile: add -Wstrict-overflow=5 to CFLAGS)
> >>
> >> The problem code is on lines 84 and 85 in
> >> libselinux/src/booleans.c:
> >>
> >> 84: for (--i; i >= 0; --i)
> >> 85: free(n[i]);
> >>
> >>
> >> It could be suppressed by something like this:
> >>
> >> --- a/libselinux/src/booleans.c
> >> +++ b/libselinux/src/booleans.c
> >> @@ -39,7 +39,7 @@ static int filename_select(const struct dirent
> >> *d)
> >> int security_get_boolean_names(char ***names, int *len) {
> >> char path[PATH_MAX];
> >> - int i, rc;
> >> + int i, j, rc;
> >> struct dirent **namelist;
> >> char **n;
> >>
> >> @@ -81,8 +81,8 @@ int security_get_boolean_names(char ***names, int
> *len)
> >> free(namelist);
> >> return rc;
> >> bad_freen:
> >> - for (--i; i >= 0; --i)
> >> - free(n[i]);
> >> + for (j = 0; j < i; j++)
> >> + free(n[j]);
> >> free(n);
> >> bad:
> >> goto out;
> >>
> >>
> >> William, what would you consider to be the right fix in this case?
> >
> > The previous code looks correct IMO, I can't see an actual problem.
> > Looks like GCC complaining incorrectly or were missing something. In
> > the case of gcc Incorrectly complaining I usually take a course of
> > action to work around it, but Im not sure how other maintainers feel about that
> @sds anything?
>
> AFAICS, the code is correct as is. Not a fan of rewriting code to appease overly
> zealous compilers...
>
So I looked at filing a bug with GCC, and one thing that helps it get looked at is sample code
to trigger the problem. I'm not even seeing a GCC 9 release, so I am assuming it's in a dev
mode?
Since you have it running could you see if you can re-produce the error in a snippet and file the bug?
I would also diff the object file with -frwapv to see if it is producing different code for that loop.
Bill
next prev parent reply other threads:[~2019-02-08 19:40 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-01 19:34 gcc 9.0.0 build issues Petr Lautrbach
2019-02-01 20:24 ` Ondrej Mosnacek
2019-02-07 12:40 ` Petr Lautrbach
2019-02-07 17:52 ` Roberts, William C
2019-02-07 18:17 ` Stephen Smalley
2019-02-07 18:18 ` Roberts, William C
2019-02-07 18:20 ` Stephen Smalley
2019-02-07 18:22 ` Roberts, William C
2019-02-08 19:40 ` Roberts, William C [this message]
2019-02-08 20:10 ` Ondrej Mosnacek
2019-02-12 16:37 ` Petr Lautrbach
2019-02-07 15:32 ` Ondrej Mosnacek
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