foo.c: In function ‘main’:
foo.c:7:9: error: expected ‘,’ or ‘;’ before ‘for’
    7 |         for(i=0;i<m-1;i++){
      |         ^~~
foo.c:7:17: error: ‘i’ undeclared (first use in this function)
    7 |         for(i=0;i<m-1;i++){
      |                 ^
foo.c:7:17: note: each undeclared identifier is reported only once for each function it appears in
foo.c:7:26: error: expected ‘;’ before ‘)’ token
    7 |         for(i=0;i<m-1;i++){
      |                          ^
      |                          ;
foo.c:7:26: error: expected statement before ‘)’ token
foo.c:8:30: error: implicit declaration of function ‘pow’ [-Wimplicit-function-declaration]
    8 |                 int ret=a[i]*pow(10,i);
      |                              ^~~
foo.c:2:1: note: include ‘<math.h>’ or provide a declaration of ‘pow’
    1 | #include <stdio.h>
  +++ |+#include <math.h>
    2 | 
foo.c:8:30: warning: incompatible implicit declaration of built-in function ‘pow’ [-Wbuiltin-declaration-mismatch]
    8 |                 int ret=a[i]*pow(10,i);
      |                              ^~~
foo.c:8:30: note: include ‘<math.h>’ or provide a declaration of ‘pow’
foo.c:8:21: warning: unused variable ‘ret’ [-Wunused-variable]
    8 |                 int ret=a[i]*pow(10,i);
      |                     ^~~
foo.c:11:16: error: ‘ret’ undeclared (first use in this function)
   11 |         return ret;
      |                ^~~
foo.c:6:13: warning: variable ‘a’ set but not used [-Wunused-but-set-variable]
    6 |         int a[5]={}
      |             ^