0_0_36720048_5845.c: In function 'sort':
0_0_36720048_5845.c:7:5: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
for (int i = 0; i < len; ++i) {
^
0_0_36720048_5845.c:7:5: note: use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code
0_0_36720048_5845.c:8:9: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
for (int j = len-1; j > i; --j) {
^
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