The declaration with extern specifies to that unit of compilation information about these arrays, but the definition (when memory is actually reserved as well) happens in another unit.
As I mentioned, GCC usually updates how it handles somethings based on the spec of the C language over time. In this particular case, the issue was caused by an updated handling of extern in GCC 10: https://gcc.gnu.org/gcc-10/porting_to.html See the "default to -fno-common" section at the very beginning of that page to understand what the change was and why it was done. Best regards, On Wed, Jul 12, 2023 at 5:08 AM James Dempsey <james.e.demp...@gmail.com> wrote: > Thank you for your quick attention to this, Luis, that certain works and > compiles successfully. > > One question, again not a C programmer, but why both `extern` the > "declaration" and move the "definition", if those are the correct terms? > > On Tue, Jul 11, 2023 at 10:05 PM Luis Felipe Strano Moraes < > luis.str...@gmail.com> wrote: > >> That is perfectly fine, the other way of fixing it would be this way >> which was apparently already committed to the git tree but no new release >> was made that includes it: >> >> http://git.savannah.gnu.org/cgit/gnugo.git/commit/?h=ttn-maint&id=54b697abcd2ccfb2fe0f5a7454da4a14118483ca >> >> The reason this error was encountered was due to changes in GCC as it >> evolves where it starts treating some things differently, and it has been a >> long time since GNU Go 3.8 was released. >> >> Best regards, >> >> >> On Tue, Jul 11, 2023 at 5:19 PM James Dempsey <james.e.demp...@gmail.com> >> wrote: >> >>> I ran into an issue with compiling GNU Go 3.8 on Amazon Linux 2023 (gcc >>> (GCC) 11.3.1 20221121 (Red Hat 11.3.1-4)). >>> >>> I receive the follow error when running `./configure` and `make`: >>> >>> gcc -g -O2 -o mkpat mkpat.o transform.o dfa.o ../utils/libutils.a -lm >>>> /usr/bin/ld: >>>> transform.o:/home/ec2-user/kgsGtp-3.5.23/gnugo-3.8/patterns/../engine/liberty.h:861: >>>> multiple definition of `meaningless_white_moves'; >>>> mkpat.o:/home/ec2-user/kgsGtp-3.5.23/gnugo-3.8/patterns/../engine/liberty.h:861: >>>> first defined here >>>> /usr/bin/ld: >>>> transform.o:/home/ec2-user/kgsGtp-3.5.23/gnugo-3.8/patterns/../engine/liberty.h:860: >>>> multiple definition of `meaningless_black_moves'; >>>> mkpat.o:/home/ec2-user/kgsGtp-3.5.23/gnugo-3.8/patterns/../engine/liberty.h:860: >>>> first defined here >>>> /usr/bin/ld: >>>> dfa.o:/home/ec2-user/kgsGtp-3.5.23/gnugo-3.8/patterns/../engine/liberty.h:861: >>>> multiple definition of `meaningless_white_moves'; >>>> mkpat.o:/home/ec2-user/kgsGtp-3.5.23/gnugo-3.8/patterns/../engine/liberty.h:861: >>>> first defined here >>>> /usr/bin/ld: >>>> dfa.o:/home/ec2-user/kgsGtp-3.5.23/gnugo-3.8/patterns/../engine/liberty.h:860: >>>> multiple definition of `meaningless_black_moves'; >>>> mkpat.o:/home/ec2-user/kgsGtp-3.5.23/gnugo-3.8/patterns/../engine/liberty.h:860: >>>> first defined here >>>> collect2: error: ld returned 1 exit status >>>> make[2]: *** [Makefile:371: mkpat] Error 1 >>>> make[2]: Leaving directory >>>> '/home/ec2-user/kgsGtp-3.5.23/gnugo-3.8/patterns' >>>> make[1]: *** [Makefile:232: all-recursive] Error 1 >>>> make[1]: Leaving directory '/home/ec2-user/kgsGtp-3.5.23/gnugo-3.8' >>>> make: *** [Makefile:168: all] Error 2 >>> >>> >>> My solution was to move the following lines from `liberty.h` to >>> `unconditional.c`: >>> >>> /* Unconditionally meaningless moves. */ >>>> int meaningless_black_moves[BOARDMAX]; >>>> int meaningless_white_moves[BOARDMAX]; >>> >>> >>> This change allowed me to compile successfully. >>> >>> I am not a C programmer. Is this a reasonable change to make >>> and does not functionally affect the program? Why was this error >>> encountered in the first place? >>> >>> Thank you. >>> _______________________________________________ >>> gnugo-devel mailing list >>> gnugo-devel@gnu.org >>> https://lists.gnu.org/mailman/listinfo/gnugo-devel >>> >> >> >> -- >> Luís Felipe Strano Moraes >> _______________________________________________ >> gnugo-devel mailing list >> gnugo-devel@gnu.org >> https://lists.gnu.org/mailman/listinfo/gnugo-devel >> > _______________________________________________ > gnugo-devel mailing list > gnugo-devel@gnu.org > https://lists.gnu.org/mailman/listinfo/gnugo-devel > -- Luís Felipe Strano Moraes
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