> -----Original Message----- > From: Stephen Smalley [mailto:sds@xxxxxxxxxxxxx] > Sent: Thursday, February 7, 2019 10:17 AM > To: Roberts, William C <william.c.roberts@xxxxxxxxx>; Petr Lautrbach > <plautrba@xxxxxxxxxx>; selinux@xxxxxxxxxxxxxxx > Cc: Ondrej Mosnacek <omosnace@xxxxxxxxxx> > 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@xxxxxxxxxx] > >> Sent: Thursday, February 7, 2019 4:40 AM > >> To: selinux@xxxxxxxxxxxxxxx > >> Cc: Petr Lautrbach <plautrba@xxxxxxxxxx>; Roberts, William C > >> <william.c.roberts@xxxxxxxxx>; Ondrej Mosnacek <omosnace@xxxxxxxxxx> > >> Subject: Re: gcc 9.0.0 build issues > >> > >> > >> Ondrej Mosnacek <omosnace@xxxxxxxxxx> writes: > >> > >>> On Fri, Feb 1, 2019 at 8:36 PM Petr Lautrbach <plautrba@xxxxxxxxxx> > >>> 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
