Determining if the strnstr exist failed with the following output: Change Dir: /home/buildroot/autobuild/instance-3/output-1/build/netopeer2-2.1.16/CMakeFiles/CMakeTmp Run Build Command(s):/usr/bin/make -f Makefile cmTC_a9da0/fast && make[1]: Entering directory '/home/buildroot/autobuild/instance-3/output-1/build/netopeer2-2.1.16/CMakeFiles/CMakeTmp' /usr/bin/make -f CMakeFiles/cmTC_a9da0.dir/build.make CMakeFiles/cmTC_a9da0.dir/build make[2]: Entering directory '/home/buildroot/autobuild/instance-3/output-1/build/netopeer2-2.1.16/CMakeFiles/CMakeTmp' Building C object CMakeFiles/cmTC_a9da0.dir/CheckSymbolExists.c.o /home/buildroot/autobuild/instance-3/output-1/host/bin/microblaze-linux-gcc --sysroot=/home/buildroot/autobuild/instance-3/output-1/host/microblaze-buildroot-linux-gnu/sysroot -D_GNU_SOURCE -D_POSIX_C_SOURCE=200809L -D__BSD_VISIBLE=1 -DNDEBUG -O2 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os -g0 -Wall -Wextra -std=gnu99 -DNDEBUG -o CMakeFiles/cmTC_a9da0.dir/CheckSymbolExists.c.o -c /home/buildroot/autobuild/instance-3/output-1/build/netopeer2-2.1.16/CMakeFiles/CMakeTmp/CheckSymbolExists.c /home/buildroot/autobuild/instance-3/output-1/build/netopeer2-2.1.16/CMakeFiles/CMakeTmp/CheckSymbolExists.c: In function 'main': /home/buildroot/autobuild/instance-3/output-1/build/netopeer2-2.1.16/CMakeFiles/CMakeTmp/CheckSymbolExists.c:8:19: error: 'strnstr' undeclared (first use in this function); did you mean 'strstr'? 8 | return ((int*)(&strnstr))[argc]; | ^~~~~~~ | strstr /home/buildroot/autobuild/instance-3/output-1/build/netopeer2-2.1.16/CMakeFiles/CMakeTmp/CheckSymbolExists.c:8:19: note: each undeclared identifier is reported only once for each function it appears in /home/buildroot/autobuild/instance-3/output-1/build/netopeer2-2.1.16/CMakeFiles/CMakeTmp/CheckSymbolExists.c:4:14: warning: parameter 'argc' set but not used [-Wunused-but-set-parameter] 4 | int main(int argc, char** argv) | ~~~~^~~~ CMakeFiles/cmTC_a9da0.dir/build.make:77: recipe for target 'CMakeFiles/cmTC_a9da0.dir/CheckSymbolExists.c.o' failed make[2]: *** [CMakeFiles/cmTC_a9da0.dir/CheckSymbolExists.c.o] Error 1 make[2]: Leaving directory '/home/buildroot/autobuild/instance-3/output-1/build/netopeer2-2.1.16/CMakeFiles/CMakeTmp' Makefile:127: recipe for target 'cmTC_a9da0/fast' failed make[1]: *** [cmTC_a9da0/fast] Error 2 make[1]: Leaving directory '/home/buildroot/autobuild/instance-3/output-1/build/netopeer2-2.1.16/CMakeFiles/CMakeTmp' File /home/buildroot/autobuild/instance-3/output-1/build/netopeer2-2.1.16/CMakeFiles/CMakeTmp/CheckSymbolExists.c: /* */ #include int main(int argc, char** argv) { (void)argv; #ifndef strnstr return ((int*)(&strnstr))[argc]; #else (void)argc; return 0; #endif }