Changed static member function that was manipulating non-static members

Description

The current state of develop does not compile in DEBUG mode because a static member function manipulates non-static members causing a compilation error.

Here is the log:

~/D/s/l/build ❯❯❯ make
[  6%] Built target zm
Scanning dependencies of target ff
[  8%] Building CXX object libff/CMakeFiles/ff.dir/algebra/curves/edwards/edwards_pairing.cpp.o
<path-to-libff>/scipr-lab/libff/libff/algebra/curves/edwards/edwards_pairing.cpp:251:20: fatal error: invalid use of member 'T' in static member function
            assert(T*Z == X*Y);
                   ^
/usr/include/assert.h:93:27: note: expanded from macro 'assert'
     (static_cast <bool> (expr)                                         \
                          ^~~~
1 error generated.
libff/CMakeFiles/ff.dir/build.make:290: recipe for target 'libff/CMakeFiles/ff.dir/algebra/curves/edwards/edwards_pairing.cpp.o' failed
make[2]: *** [libff/CMakeFiles/ff.dir/algebra/curves/edwards/edwards_pairing.cpp.o] Error 1
CMakeFiles/Makefile2:755: recipe for target 'libff/CMakeFiles/ff.dir/all' failed
make[1]: *** [libff/CMakeFiles/ff.dir/all] Error 2
Makefile:160: recipe for target 'all' failed
make: *** [all] Error 2

Here are the problematic lines: https://github.com/scipr-lab/libff/blob/develop/libff/algebra/curves/edwards/edwards_pairing.cpp#L452-L471 (same for mnt4/mnt6) The error is triggered because of https://github.com/scipr-lab/libff/blob/develop/libff/algebra/curves/edwards/edwards_pairing.cpp#L505-L507 which is added to the code when we compile in debug mode only.

As it clearly seems that this invariant check function should not be a static one (it needs an instance to be called upon), I removed the static keyword. The compilation now passes in DEBUG mode

Before we can merge this PR, please make sure that all the following items have been checked off. If any of the checklist items are not applicable, please leave them but write a little note why.

[ ] Targeted PR against correct branch (develop)
[ ] Linked to Github issue with discussion and accepted design OR have an explanation in the PR that describes this work.
[ ] Wrote unit tests
[ ] Updated relevant documentation in the code
[ ] Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
[ ] Re-reviewed Files changed in the Github PR explorer

scipr-lab / libff

Changed static member function that was manipulating non-static members #93

Description