On 10/18/2011 10:09 AM, Wen Congyang wrote:
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:
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
On 10/17/2011 10:17 AM, Alex Jia wrote: 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 Chonyang, thanks for your reply and good example.
Regards, Alex
I am still investigating this problem.
Thanks Wen Congyang
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