Compiler warning in master branch - Mailing list pgsql-hackers

I see this when I build at -O2 from master's tip:

gcc -O2 -Wall -Wmissing-prototypes -Wpointer-arith
-Wdeclaration-after-statement -Wendif-labels
-Wmissing-format-attribute -Wformat-security -fno-strict-aliasing
-fwrapv -fexcess-precision=standard -Werror -I../../../../src/include
-D_FORTIFY_SOURCE=2 -D_GNU_SOURCE -I/usr/include/libxml2   -c -o
brin_revmap.o brin_revmap.c -MMD -MP -MF .deps/brin_revmap.Po
brin_revmap.c: In function ‘brinRevmapExtend’:
brin_revmap.c:113:14: error: variable ‘mapBlk’ set but not used
[-Werror=unused-but-set-variable] BlockNumber mapBlk;             ^

I'm using gcc 4.8.2 here.

--
Peter Geoghegan