Error "undefined reference to" raised when compile kaezip_perf.c

[huangtianhua]

root@hadoop-kae:/opt/KAE_repos/hth/kaezip2/test# make
gcc -g -lz -Wall -L/usr/local/kaezip/lib -I /usr/local/kaezip/include/ -o kaezip_perf kaezip_perf.c
kaezip_perf.c: In function ‘do_compress_perf’:
kaezip_perf.c:122:9: warning: unused variable ‘i’ [-Wunused-variable]
     int i = 0;
         ^
kaezip_perf.c: In function ‘do_decompress_perf’:
kaezip_perf.c:147:12: warning: unused variable ‘j’ [-Wunused-variable]
     int i, j;
            ^
kaezip_perf.c:147:9: warning: unused variable ‘i’ [-Wunused-variable]
     int i, j;
         ^
/tmp/ccWTksRC.o: In function `get_decompress_input':
/opt/KAE_repos/hth/kaezip2/test/kaezip_perf.c:46: undefined reference to `compressBound'
/opt/KAE_repos/hth/kaezip2/test/kaezip_perf.c:49: undefined reference to `compress2'
/tmp/ccWTksRC.o: In function `do_multi_perf':
/opt/KAE_repos/hth/kaezip2/test/kaezip_perf.c:79: undefined reference to `compressBound'
/opt/KAE_repos/hth/kaezip2/test/kaezip_perf.c:80: undefined reference to `compress2'
/opt/KAE_repos/hth/kaezip2/test/kaezip_perf.c:86: undefined reference to `uncompress'
/tmp/ccWTksRC.o: In function `do_compress_perf':
/opt/KAE_repos/hth/kaezip2/test/kaezip_perf.c:128: undefined reference to `compressBound'
collect2: error: ld returned 1 exit status
makefile:14: recipe for target 'kaezip_perf' failed
make: *** [kaezip_perf] Error 1

root@hadoop-kae:/opt/KAE_repos/hth/kaezip2/test# gcc --version
gcc (Ubuntu/Linaro 7.4.0-1ubuntu1~18.04.1) 7.4.0
Copyright (C) 2017 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Then I put -lz option after kaezip_perf.c, it works.

According the docs https://gcc.gnu.org/onlinedocs/gcc-7.4.0/gcc/Link-Options.html#Link-Options :
It makes a difference where in the command you write this option; the linker searches and processes libraries and object files in the order they are specified. Thus, ‘foo.o -lz bar.o’ searches library ‘z’ after file foo.o but before bar.o. If bar.o refers to functions in ‘z’, those functions may not be loaded.

[Yikun]

^ 在ubuntu 18.04上面，会出现这个问题，解决方案是把lz放到最后。centos之前我试过没问题。

https://github.com/kunpengcompute/KAEzip/blob/master/test/makefile#L14

gcc $(CFLAGS) $(LDFLAGS) $(INCDIR) -o kaezip_perf $(objects)

把这个修改为

gcc $(LDFLAGS) $(INCDIR) -o kaezip_perf $(objects) $(CFLAGS)

或者把-lz放到独立的FLAGS里，后置即可。

[1] https://stackoverflow.com/questions/11893996/why-does-the-order-of-l-option-in-gcc-matter

[Yikun]

#10

可以看这个PR，复现了这个问题~