demo.c: In function ‘test_1’:
demo.c:14:10: warning: implicit declaration of function ‘malloc’ [-Wimplicit-function-declaration]
   14 |   return malloc (4096);
      |          ^~~~~~
demo.c:3:1: note: include ‘<stdlib.h>’ or provide a declaration of ‘malloc’
    2 | #include <stdio.h>
  +++ |+#include <stdlib.h>
    3 | 
fix-it:"demo.c":{3:1-3:1}:"#include <stdlib.h>\n"
demo.c:14:10: warning: incompatible implicit declaration of built-in function ‘malloc’ [-Wbuiltin-declaration-mismatch]
   14 |   return malloc (4096);
      |          ^~~~~~
demo.c:14:10: note: include ‘<stdlib.h>’ or provide a declaration of ‘malloc’
demo.c: In function ‘test_2a’:
demo.c:20:21: error: ‘struct vert’ has no member named ‘colour’; did you mean ‘color’?
   20 |   /* 🙂 🙂 🙂 */ v->colour = 0;
      |                     ^~~~~~
      |                     color
fix-it:"demo.c":{20:21-20:27}:"color"
demo.c: In function ‘test_2b’:
demo.c:26:18: error: ‘struct vert’ has no member named ‘colour’; did you mean ‘color’?
   26 |   /* π π π */ v->colour = 0;
      |                  ^~~~~~
      |                  color
fix-it:"demo.c":{26:18-26:24}:"color"
demo.c: In function ‘test_2c’:
demo.c:32:21: error: ‘struct vert’ has no member named ‘colour’; did you mean ‘color’?
   32 |   /* 文字化け */ v->colour = 0;
      |                     ^~~~~~
      |                     color
fix-it:"demo.c":{32:21-32:27}:"color"
demo.c: In function ‘test_3’:
demo.c:38:14: error: ‘struct vert’ has no member named ‘colour’; did you mean ‘color’?
   38 |           v->colour = 0;
      |              ^~~~~~
      |              color
fix-it:"demo.c":{38:14-38:20}:"color"
demo.c: In function ‘test_4’:
demo.c:44:10: error: ‘struct vert’ has no member named ‘colour’; did you mean ‘color’?
   44 |   if (v->colour) v->colour += 2;
      |          ^~~~~~
      |          color
fix-it:"demo.c":{44:10-44:16}:"color"
demo.c:44:21: error: ‘struct vert’ has no member named ‘colour’; did you mean ‘color’?
   44 |   if (v->colour) v->colour += 2;
      |                     ^~~~~~
      |                     color
fix-it:"demo.c":{44:21-44:27}:"color"
demo.c: In function ‘test_5’:
demo.c:51:10: error: ‘two_pi’ undeclared (first use in this function); did you mean ‘two_π’?
   51 |   return two_pi;
      |          ^~~~~~
      |          two_π
fix-it:"demo.c":{51:10-51:16}:"two_\317\200"
demo.c:51:10: note: each undeclared identifier is reported only once for each function it appears in