Bug#887692: casync: FTBFS and Debci failure with glibc 2.26

[Adrian Bunk]

Source: casync
Version: 2-1
Severity: serious

https://ci.debian.net/packages/c/casync/unstable/amd64/
https://tests.reproducible-builds.org/debian/rb-pkg/unstable/amd64/casync.html

...
FAILED: src/shared at sta/caremote.c.o 
cc  -Isrc/shared at sta -Isrc -I../src -fdiagnostics-color=always -pipe -D_FILE_OFFSET_BITS=64 -std=gnu99 -Wextra -Werror=undef -Werror=format=2 -Wformat-security -Wformat-nonliteral -Wlogical-op -Wmissing-include-dirs -Werror=old-style-definition -Werror=pointer-arith -Winit-self -Wdeclaration-after-statement -Wfloat-equal -Wsuggest-attribute=noreturn -Werror=missing-prototypes -Werror=implicit-function-declaration -Werror=missing-declarations -Werror=return-type -Werror=incompatible-pointer-types -Werror=shadow -Wstrict-prototypes -Wredundant-decls -Wmissing-noreturn -Wendif-labels -Wstrict-aliasing=2 -Wwrite-strings -Wno-unused-parameter -Wno-missing-field-initializers -Wno-unused-result -Werror=overflow -Werror=sign-compare -Wdate-time -Wnested-externs -ffast-math -fno-common -fdiagnostics-show-option -fno-strict-aliasing -fvisibility=hidden -fstack-protector -fstack-protector-strong -fPIE --param=ssp-buffer-size=4 -include config.h -g -O2 -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2 -fPIC -MMD -MQ 'src/shared at sta/caremote.c.o' -MF 'src/shared at sta/caremote.c.o.d' -o 'src/shared at sta/caremote.c.o' -c ../src/caremote.c
In file included from ../src/caformat-util.h:7:0,
                 from ../src/caremote.c:8:
../src/caremote.c: In function ‘ca_remote_forget_chunk’:
../src/util.h:471:13: error: argument 1 null where non-null expected [-Werror=nonnull]
         if (strncmp(s, prefix, l) == 0)
             ^~~~~~~~~~~~~~~~~~~~~
In file included from ../src/util.h:12:0,
                 from ../src/caformat-util.h:7,
                 from ../src/caremote.c:8:
/usr/include/string.h:139:12: note: in a call to function ‘strncmp’ declared here
 extern int strncmp (const char *__s1, const char *__s2, size_t __n)
            ^~~~~~~
cc1: some warnings being treated as errors