foo.cc: In function ‘int main()’:
foo.cc:15:14: warning: ‘fenmu’ may be used uninitialized [-Wmaybe-uninitialized]
   15 |         b2=b2*fenmu/a2;
      |            ~~^~~~~~
foo.cc:5:31: note: ‘fenmu’ was declared here
    5 |     int b1,a1,b2,a2,gbs,fenzi,fenmu;
      |                               ^~~~~