Re: [libvirt] Compiler warnings

At 10/18/2011 09:32 AM, Wen Congyang Write: > At 10/18/2011 01:04 AM, Eric Blake Write: >> On 10/17/2011 11:03 AM, Eric Blake wrote: >>> On 10/17/2011 10:17 AM, Alex Jia wrote: >>>> Eric, >>>> It's latest libvirt upstream, current commit id is commit 0a71c79. >>>> >>>> # rpm -q glibc >>>> glibc-2.12-1.42.el6.x86_64 >>>> >>>> 430 if (strchr(toescape, *cur)) >>>>>> CC libvirt_util_la-buf.lo >>>>>> util/buf.c: In function 'virBufferEscape': >>>>>> util/buf.c:430: warning: logical '&&' with non-zero constant will >>>>>> always >>>>>> evaluate as true [-Wlogical-op] >>> Something's screwy. There's no&& in that line, unless strchr() is a >>> macro based on your particular compilation flags. I'm suspecting that >>> this is a case of -D_FORTIFY_SOURCE going awry. I don't see how this >>> could possibly be a libvirt issue; more likely, it is an issue with the >>> choice of compiler flags you are using, coupled with an issue in the >>> system headers causing the preprocessor to expand strchr() into >>> something that tickles a spurious gcc warning. >> Just to make sure, could you show 'make V=1' output, so we know exactly >> which compiler flags are in effect? >> > I can reproduce this problem, here is 'make V=1' output: > > ===================================================== > make[3]: Entering directory `/root/rpmbuild/BUILD/libvirt-0.9.6/src' > /bin/sh ../libtool --tag=CC --mode=compile gcc -std=gnu99 -DHAVE_CONFIG_H -I. -I.. -I../gnulib/lib -I../gnulib/lib -I../include -I../src/util -I../include -DIN_LIBVIRT -I/usr/include/libxml2 -Wall -W -Wformat-y2k -Wformat-security -Winit-self -Wmissing-include-dirs -Wunused -Wunknown-pragmas -Wstrict-aliasing -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-align -Wwrite-strings -Wlogical-op -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 -Wmudflap -Wpacked-bitfield-compat -Wsync-nand -Wattributes -Wcoverage-mismatch -Wmultichar -Wno-missing-field-initializers -Wno-sign-compare -Wframe-larger-than=4096 -Wp,-D_FORTIFY_SOURCE=2 -fstack-protector-all --param=ssp-buffer-size=4 -fexceptions -fasynchronous-unwind-tables -fdiagnostics -s > how-option -funit-at-a-time -Werror -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic -MT libvirt_util_la-buf.lo -MD -MP -MF .deps/libvirt_util_la-buf.Tpo -c -o libvirt_util_la-buf.lo `test -f 'util/buf.c' || echo './'`util/buf.c > libtool: compile: gcc -std=gnu99 -DHAVE_CONFIG_H -I. -I.. -I../gnulib/lib -I../gnulib/lib -I../include -I../src/util -I../include -DIN_LIBVIRT -I/usr/include/libxml2 -Wall -W -Wformat-y2k -Wformat-security -Winit-self -Wmissing-include-dirs -Wunused -Wunknown-pragmas -Wstrict-aliasing -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-align -Wwrite-strings -Wlogical-op -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 -Wmudflap -Wpacked-bitfield-compat -Wsync-nand -Wattributes -Wcoverage-mismatch -Wmultichar -Wno-missing-field-initializers -Wno-sign-compare -Wframe-larger-than=4096 -Wp,-D_FORTIFY_SOURCE=2 -fstack-protector-all --param=ssp-buffer-size=4 -fexceptions -fasynchronous-unwind-tables -fdiagnostics-show-option -funit-at-a-time -Werro r > -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic -MT libvirt_util_la-buf.lo -MD -MP -MF .deps/libvirt_util_la-buf.Tpo -c util/buf.c -fPIC -DPIC -o .libs/libvirt_util_la-buf.o > cc1: warnings being treated as errors > util/buf.c: In function 'virBufferEscape': > util/buf.c:430: error: logical '&&' with non-zero constant will always evaluate as true [-Wlogical-op] > make[3]: *** [libvirt_util_la-buf.lo] Error 1 > ===================================================== > > If I remove -O2, I can build util/buf.c. I test strchr in a small program: ===================================================== # cat test.c #include<stdio.h> #include<string.h> int main() { char *s = "abcdefg"; int chr = (int)'d'; char *d; d = strchr(s, chr); if (d) printf("%s\n", d); return 0; } # gcc -std=c99 -Wall -o test test.c -Wlogical-op -Werror # gcc -std=c99 -O2 -Wall -o test test.c -Wlogical-op -Werror cc1: warnings being treated as errors test.c: In function ‘main’: test.c:9: error: logical ‘&&’ with non-zero constant will always evaluate as true # gcc -std=c99 -Wall -o test test.c -Wlogical-op -Werror # gcc -std=c99 -Wall -o test test.c -Werror ===================================================== The building failed only when '-O2' and '-Wlogical-op' are specified at the same time. Thanks Wen Congyang

> I am still investigating this problem. > > Thanks > Wen Congyang > > -- > libvir-list mailing list > libvir-list(a)redhat.com > https://www.redhat.com/mailman/listinfo/libvir-list > -- libvir-list mailing list libvir-list(a)redhat.com https://www.redhat.com/mailman/listinfo/libvir-list