We are seeing build failure of xen-unstable for the last couple of changesets, in tools/blktap/drivers for block-qcow2.c

This seems to be because of the fact that the compile line uses these flags, -Werror -Wno-unused, treating warnings as errors and aborting the compilation.

The Makefile in tools/blktap/drivers has these CFLAGS set: CFLAGS += -Werror CFLAGS += -Wno-unused

gcc -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic -m64 -fno-strict-aliasing -std=gnu99 -Wall -Wstrict-prototypes -Wno-unused-value -Wdeclaration-after-statement -m64 -fno-strict-aliasing -std=gnu99 -Wall -Wstrict-prototypes -Wno-unused-value -Wdeclaration-after-statement -m64 -fno-strict-aliasing -std=gnu99 -Wall -Wstrict-prototypes -Wno-unused-value -Wdeclaration-after-statement -D__XEN_TOOLS__ -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -m64 -fno-strict-aliasing -std=gnu99 -Wall -Wstrict-prototypes -Wno-unused-value -Wdeclaration-after-statement -D__XEN_TOOLS__ -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -m64 -fno-strict-aliasing -std=gnu99 -Wall -Wstrict-prototypes -Wno-unused-value -Wdeclaration-after-statement -D__XEN_TOOLS__ -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -m64 -fno-strict-aliasing -std=gnu99 -Wall -Wstrict-prototypes -Wno-unused-value -Wdeclaration-after-statement -D__XEN_TOOLS__ -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -Werror -Wno-unused -I../../../tools/libxc -I../../../tools/include -I ../../libaio/src -I.. -I../lib -I../../../tools/include -I. -I../../xenstore -D_GNU_SOURCE -Wp,-MD,.block-qcow2.o.d -c -o block-qcow2.o block-qcow2.c cc1: warnings being treated as errors block-qcow2.c: In function ‘qcow2_create’: block-qcow2.c:1312: warning: ignoring return value of ‘write’, declared with attribute warn_unused_result block-qcow2.c:1314: warning: ignoring return value of ‘write’, declared with attribute warn_unused_result block-qcow2.c:1319: warning: ignoring return value of ‘write’, declared with attribute warn_unused_result block-qcow2.c:1322: warning: ignoring return value of ‘write’, declared with attribute warn_unused_result block-qcow2.c:1325: warning: ignoring return value of ‘write’, declared with attribute warn_unused_result block-qcow2.c: In function ‘qcow_write_compressed’: block-qcow2.c:1354: warning: ignoring return value of ‘ftruncate’, declared with attribute warn_unused_result ..... .....

Thanks, Maturi