Build failure with Clang 15 or later

[RyanGlScott]

Building libpoly with Clang 15 or later fails due to the -Wunused-but-set-variable warning being triggered, which causes -Werror to fail. To reproduce the error:

$ cd build/

$ CC=~/Software/clang+llvm-15.0.6/bin/clang CXX=~/Software/clang+llvm-15.0.6/bin/clang++ cmake .. 
-- The C compiler identification is Clang 15.0.6
-- The CXX compiler identification is Clang 15.0.6
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /home/ryanglscott/Software/clang+llvm-15.0.6/bin/clang - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /home/ryanglscott/Software/clang+llvm-15.0.6/bin/clang++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- GMP headers: /usr/include/x86_64-linux-gnu
-- GMP library: /usr/lib/x86_64-linux-gnu/libgmp.so
-- Looking for open_memstream
-- Looking for open_memstream - found
-- Found PythonInterp: /usr/bin/python3.10 (found version "3.10.6") 
-- Found PythonLibs: /usr/lib/x86_64-linux-gnu/libpython3.10.so (found version "3.10.6") 
-- Configuring done
-- Generating done
-- Build files have been written to: /home/ryanglscott/Documents/Hacking/Haskell/libpoly/build

$ make -j8
[  1%] Building C object src/CMakeFiles/static_pic_poly.dir/utils/assignment.c.o
[  1%] Building C object src/CMakeFiles/poly.dir/utils/debug_trace.c.o
[  1%] Building C object src/CMakeFiles/static_pic_poly.dir/utils/debug_trace.c.o
[  1%] Building C object src/CMakeFiles/poly.dir/utils/assignment.c.o
[  1%] Building C object src/CMakeFiles/poly.dir/utils/output.c.o
[  2%] Building C object src/CMakeFiles/poly.dir/utils/statistics.c.o
[  2%] Building C object src/CMakeFiles/static_pic_poly.dir/utils/statistics.c.o
[  2%] Building C object src/CMakeFiles/static_poly.dir/utils/debug_trace.c.o
[  3%] Building C object src/CMakeFiles/static_pic_poly.dir/utils/output.c.o
[  4%] Building C object src/CMakeFiles/poly.dir/utils/sign_condition.c.o
[  5%] Building C object src/CMakeFiles/static_pic_poly.dir/utils/sign_condition.c.o
[  5%] Building C object src/CMakeFiles/static_poly.dir/utils/assignment.c.o
[  5%] Building C object src/CMakeFiles/poly.dir/utils/u_memstream.c.o
[  6%] Building C object src/CMakeFiles/poly.dir/number/integer.c.o
[  7%] Building C object src/CMakeFiles/static_pic_poly.dir/utils/u_memstream.c.o
[  7%] Building C object src/CMakeFiles/static_pic_poly.dir/number/integer.c.o
[  7%] Building C object src/CMakeFiles/poly.dir/number/rational.c.o
[  8%] Building C object src/CMakeFiles/poly.dir/number/algebraic_number.c.o
[  8%] Building C object src/CMakeFiles/poly.dir/number/dyadic_rational.c.o
[  9%] Building C object src/CMakeFiles/static_pic_poly.dir/number/rational.c.o
[ 10%] Building C object src/CMakeFiles/static_poly.dir/utils/output.c.o
[ 10%] Building C object src/CMakeFiles/static_poly.dir/utils/statistics.c.o
[ 11%] Building C object src/CMakeFiles/poly.dir/number/value.c.o
[ 11%] Building C object src/CMakeFiles/static_poly.dir/utils/sign_condition.c.o
[ 11%] Building C object src/CMakeFiles/static_pic_poly.dir/number/dyadic_rational.c.o
[ 12%] Building C object src/CMakeFiles/static_poly.dir/utils/u_memstream.c.o
[ 12%] Building C object src/CMakeFiles/static_poly.dir/number/integer.c.o
[ 13%] Building C object src/CMakeFiles/static_pic_poly.dir/number/algebraic_number.c.o
[ 14%] Building C object src/CMakeFiles/static_poly.dir/number/rational.c.o
[ 14%] Building C object src/CMakeFiles/static_poly.dir/number/dyadic_rational.c.o
[ 14%] Building C object src/CMakeFiles/poly.dir/interval/interval.c.o
[ 15%] Building C object src/CMakeFiles/poly.dir/interval/arithmetic.c.o
[ 16%] Building C object src/CMakeFiles/static_poly.dir/number/algebraic_number.c.o
[ 16%] Building C object src/CMakeFiles/static_pic_poly.dir/number/value.c.o
[ 16%] Building C object src/CMakeFiles/static_poly.dir/number/value.c.o
[ 17%] Building C object src/CMakeFiles/static_pic_poly.dir/interval/interval.c.o
[ 18%] Building C object src/CMakeFiles/static_poly.dir/interval/interval.c.o
[ 18%] Building C object src/CMakeFiles/static_poly.dir/interval/arithmetic.c.o
[ 18%] Building C object src/CMakeFiles/poly.dir/variable/variable_db.c.o
[ 19%] Building C object src/CMakeFiles/poly.dir/variable/variable_list.c.o
[ 19%] Building C object src/CMakeFiles/poly.dir/variable/variable_order.c.o
[ 20%] Building C object src/CMakeFiles/static_poly.dir/variable/variable_db.c.o
[ 20%] Building C object src/CMakeFiles/static_pic_poly.dir/interval/arithmetic.c.o
[ 20%] Building C object src/CMakeFiles/static_poly.dir/variable/variable_list.c.o
[ 21%] Building C object src/CMakeFiles/static_pic_poly.dir/variable/variable_db.c.o
[ 21%] Building C object src/CMakeFiles/static_pic_poly.dir/variable/variable_order.c.o
[ 21%] Building C object src/CMakeFiles/static_pic_poly.dir/variable/variable_list.c.o
[ 22%] Building C object src/CMakeFiles/poly.dir/upolynomial/umonomial.c.o
[ 23%] Building C object src/CMakeFiles/static_poly.dir/variable/variable_order.c.o
[ 24%] Building C object src/CMakeFiles/static_pic_poly.dir/upolynomial/umonomial.c.o
[ 24%] Building C object src/CMakeFiles/static_poly.dir/upolynomial/umonomial.c.o
[ 25%] Building C object src/CMakeFiles/static_poly.dir/upolynomial/upolynomial.c.o
[ 25%] Building C object src/CMakeFiles/static_poly.dir/upolynomial/output.c.o
[ 25%] Building C object src/CMakeFiles/static_pic_poly.dir/upolynomial/upolynomial.c.o
[ 26%] Building C object src/CMakeFiles/static_poly.dir/upolynomial/upolynomial_dense.c.o
[ 26%] Building C object src/CMakeFiles/static_poly.dir/upolynomial/bounds.c.o
[ 26%] Building C object src/CMakeFiles/poly.dir/upolynomial/upolynomial.c.o
[ 27%] Building C object src/CMakeFiles/static_pic_poly.dir/upolynomial/output.c.o
[ 27%] Building C object src/CMakeFiles/static_pic_poly.dir/upolynomial/upolynomial_dense.c.o
[ 27%] Building C object src/CMakeFiles/static_poly.dir/upolynomial/gcd.c.o
[ 28%] Building C object src/CMakeFiles/static_poly.dir/upolynomial/factors.c.o
[ 29%] Building C object src/CMakeFiles/poly.dir/upolynomial/output.c.o
[ 29%] Building C object src/CMakeFiles/static_poly.dir/upolynomial/factorization.c.o
[ 29%] Building C object src/CMakeFiles/poly.dir/upolynomial/upolynomial_dense.c.o
[ 30%] Building C object src/CMakeFiles/poly.dir/upolynomial/bounds.c.o
[ 31%] Building C object src/CMakeFiles/static_poly.dir/upolynomial/root_finding.c.o
[ 31%] Building C object src/CMakeFiles/poly.dir/upolynomial/gcd.c.o
[ 32%] Building C object src/CMakeFiles/static_pic_poly.dir/upolynomial/bounds.c.o
[ 32%] Building C object src/CMakeFiles/static_poly.dir/polynomial/monomial.c.o
[ 32%] Building C object src/CMakeFiles/static_pic_poly.dir/upolynomial/gcd.c.o
/home/ryanglscott/Documents/Hacking/Haskell/libpoly/src/upolynomial/factorization.c:1269:7: error: variable 'enabled_count' set but not used [-Werror,-Wunused-but-set-variable]
  int enabled_count = 0;
      ^
1 error generated.
make[2]: *** [src/CMakeFiles/static_poly.dir/build.make:398: src/CMakeFiles/static_poly.dir/upolynomial/factorization.c.o] Error 1
make[2]: *** Waiting for unfinished jobs....
[ 33%] Building C object src/CMakeFiles/static_pic_poly.dir/upolynomial/factors.c.o
make[1]: *** [CMakeFiles/Makefile2:256: src/CMakeFiles/static_poly.dir/all] Error 2
make[1]: *** Waiting for unfinished jobs....
[ 33%] Building C object src/CMakeFiles/static_pic_poly.dir/upolynomial/factorization.c.o
[ 34%] Building C object src/CMakeFiles/poly.dir/upolynomial/factors.c.o
[ 34%] Building C object src/CMakeFiles/poly.dir/upolynomial/factorization.c.o
[ 35%] Building C object src/CMakeFiles/static_pic_poly.dir/upolynomial/root_finding.c.o
[ 35%] Building C object src/CMakeFiles/poly.dir/upolynomial/root_finding.c.o
[ 36%] Building C object src/CMakeFiles/poly.dir/polynomial/monomial.c.o
[ 36%] Building C object src/CMakeFiles/static_pic_poly.dir/polynomial/monomial.c.o
[ 36%] Building C object src/CMakeFiles/poly.dir/polynomial/coefficient.c.o
[ 37%] Building C object src/CMakeFiles/poly.dir/polynomial/output.c.o
/home/ryanglscott/Documents/Hacking/Haskell/libpoly/src/upolynomial/factorization.c:1269:7: error: variable 'enabled_count' set but not used [-Werror,-Wunused-but-set-variable]
  int enabled_count = 0;
      ^
1 error generated.
make[2]: *** [src/CMakeFiles/poly.dir/build.make:398: src/CMakeFiles/poly.dir/upolynomial/factorization.c.o] Error 1
make[2]: *** Waiting for unfinished jobs....
[ 38%] Building C object src/CMakeFiles/static_pic_poly.dir/polynomial/coefficient.c.o
[ 38%] Building C object src/CMakeFiles/static_pic_poly.dir/polynomial/output.c.o
/home/ryanglscott/Documents/Hacking/Haskell/libpoly/src/upolynomial/factorization.c:1269:7: error: variable 'enabled_count' set but not used [-Werror,-Wunused-but-set-variable]
  int enabled_count = 0;
      ^
1 error generated.
[ 39%] Building C object src/CMakeFiles/static_pic_poly.dir/polynomial/gcd.c.o
make[2]: *** [src/CMakeFiles/static_pic_poly.dir/build.make:398: src/CMakeFiles/static_pic_poly.dir/upolynomial/factorization.c.o] Error 1
make[2]: *** Waiting for unfinished jobs....
make[1]: *** [CMakeFiles/Makefile2:204: src/CMakeFiles/poly.dir/all] Error 2
make[1]: *** [CMakeFiles/Makefile2:308: src/CMakeFiles/static_pic_poly.dir/all] Error 2
make: *** [Makefile:146: all] Error 2

This was originally discovered in a CVC5 context in cvc5/cvc5#9265. CVC5 works around the issue by applying the patch in cvc5/cvc5#9266, so a similar fix would likely work here.

[ianamason]

Might want to update this too @ahmed-irfan

https://github.com/SRI-CSL/homebrew-sri-csl