foo.c: In function 'main':
foo.c:10:20: error: 'x1' undeclared (first use in this function); did you mean 'y1'?
   10 |     printf("y1=%d",x1+x2
      |                    ^~
      |                    y1
foo.c:10:20: note: each undeclared identifier is reported only once for each function it appears in
foo.c:10:23: error: 'x2' undeclared (first use in this function); did you mean 'y2'?
   10 |     printf("y1=%d",x1+x2
      |                       ^~
      |                       y2
foo.c:10:25: error: expected ')' before string constant
   10 |     printf("y1=%d",x1+x2
      |           ~             ^
      |                         )
   11 |                   "y2=%d",x1*x2
      |                   ~~~~~~~
foo.c:8:13: warning: unused variable 'y3' [-Wunused-variable]
    8 |         int y3;
      |             ^~
foo.c:7:13: warning: unused variable 'y2' [-Wunused-variable]
    7 |         int y2;
      |             ^~
foo.c:6:13: warning: unused variable 'y1' [-Wunused-variable]
    6 |         int y1;
      |             ^~
foo.c:5:13: warning: unused variable 'x1\U0000ff0cx2' [-Wunused-variable]
    5 |         int x1，x2;
      |             ^~~~~~

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