Re: [libvirt] Compiler warnings
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 -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 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 am still investigating this problem.
Thanks
Wen Congyang