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Ian Jackson authored
gcc -O1 -fno-omit-frame-pointer -m32 -march=i686 -g -fno-strict-aliasing -std=gnu99 -Wall -Wstrict-prototypes -Wdeclaration-after-statement -D__XEN_TOOLS__ -MMD -MF .block-remus.o.d -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -fno-optimize-sibling-calls -mno-tls-direct-seg-refs -Werror -g -Wno-unused -fno-strict-aliasing -I../include -I../drivers -I/home/osstest/build.12828.build-i386/xen-unstable/tools/blktap2/drivers/../../../tools/libxc -I/home/osstest/build.12828.build-i386/xen-unstable/tools/blktap2/drivers/../../../tools/include -D_GNU_SOURCE -DUSE_NFS_LOCKS -c -o block-remus.o block-remus.c block-remus.c: In function 'ramdisk_flush': block-remus.c:508: error: 'buf' may be used uninitialized in this function make[5]: *** [block-remus.o] Error 1 This is because gcc can see that merge_requests doesn't always set *mergedbuf but gcc isn't able to prove that it always does so if merge_requests returns 0 and that in that case the value of ramdisk_flush::buf isn't used. This is too useful a warning to disable, despite the occasional false positive of this form. The conventional approach is to suppress the warning by explicitly initialising the variable to 0. This has just come to light because 25275:27d63b9f111a reenabled optimisation for this area of code, and gcc's data flow analysis (which is required to trigger the uninitialised variable warning) only occurs when optimisation is turned on. Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
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