"Roberts, William C" <william.c.roberts@xxxxxxxxx> writes: >> -----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 Fedora gcc is built with --with-bugurl=http://bugzilla.redhat.com/bugzilla therefore I filed bug there: https://bugzilla.redhat.com/show_bug.cgi?id=1676607 Petr
