/in/foo.cc:1:9: error: #include expects "FILENAME" or <FILENAME>
 #include&lt;iostream&gt;
         ^
/in/foo.cc: In function 'char* mul(char*, char*)':
/in/foo.cc:6:19: error: 'strlen' was not declared in this scope
  int lena=strlen(a)-1,lenb=strlen(b)-1,n=0,i,j,t;
                   ^
/in/foo.cc:8:6: error: 'i' was not declared in this scope
  for(i=lena;i&gt;=0;i--)
      ^
/in/foo.cc:8:15: error: 'gt' was not declared in this scope
  for(i=lena;i&gt;=0;i--)
               ^~
/in/foo.cc:8:18: error: expected primary-expression before '=' token
  for(i=lena;i&gt;=0;i--)
                  ^
/in/foo.cc:8:20: error: expected ')' before ';' token
  for(i=lena;i&gt;=0;i--)
                    ^
/in/foo.cc:8:2: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
  for(i=lena;i&gt;=0;i--)
  ^~~
/in/foo.cc:8:21: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'for'
  for(i=lena;i&gt;=0;i--)
                     ^
/in/foo.cc:8:21: error: 'i' was not declared in this scope
/in/foo.cc:27:11: error: 'n' was not declared in this scope
  while(!s[n])
           ^
/in/foo.cc:29:5: error: 'n' was not declared in this scope
  if(n&lt;0)
     ^
/in/foo.cc:29:7: error: 'lt' was not declared in this scope
  if(n&lt;0)
       ^~
/in/foo.cc:29:9: error: expected ')' before ';' token
  if(n&lt;0)
         ^
/in/foo.cc:29:2: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
  if(n&lt;0)
  ^~
/in/foo.cc:29:10: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'if'
  if(n&lt;0)
          ^
/in/foo.cc:29:11: error: expected ';' before ')' token
  if(n&lt;0)
           ^
/in/foo.cc:30:5: warning: statement has no effect [-Wunused-value]
  n=0;
     ^
/in/foo.cc:31:12: error: 'lt' was not declared in this scope
  for(i=0;i&lt;=n;i++)
            ^~
/in/foo.cc:31:15: error: expected primary-expression before '=' token
  for(i=0;i&lt;=n;i++)
               ^
/in/foo.cc:31:16: error: 'n' was not declared in this scope
  for(i=0;i&lt;=n;i++)
                ^
/in/foo.cc:31:17: error: expected ')' before ';' token
  for(i=0;i&lt;=n;i++)
                 ^
/in/foo.cc:31:2: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
  for(i=0;i&lt;=n;i++)
  ^~~
/in/foo.cc:31:18: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'for'
  for(i=0;i&lt;=n;i++)
                  ^
/in/foo.cc:34:11: error: '_strrev' was not declared in this scope
  _strrev(c);
           ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:40:8: error: 'cin' was not declared in this scope
  while(cin&gt;&gt;a&gt;&gt;b)
        ^~~
/in/foo.cc:40:12: error: 'gt' was not declared in this scope
  while(cin&gt;&gt;a&gt;&gt;b)
            ^~
/in/foo.cc:40:14: error: expected ')' before ';' token
  while(cin&gt;&gt;a&gt;&gt;b)
              ^
/in/foo.cc:40:2: warning: this 'while' clause does not guard... [-Wmisleading-indentation]
  while(cin&gt;&gt;a&gt;&gt;b)
  ^~~~~
/in/foo.cc:40:15: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'while'
  while(cin&gt;&gt;a&gt;&gt;b)
               ^
/in/foo.cc:40:16: error: 'gt' was not declared in this scope
  while(cin&gt;&gt;a&gt;&gt;b)
                ^~
/in/foo.cc:40:29: error: expected ';' before ')' token
  while(cin&gt;&gt;a&gt;&gt;b)
                             ^
/in/foo.cc:41:9: warning: statement has no effect [-Wunused-value]
  cout&lt;&lt;mul(a,b)&lt;&lt;endl;
         ^
/in/foo.cc:41:11: error: 'lt' was not declared in this scope
  cout&lt;&lt;mul(a,b)&lt;&lt;endl;
           ^~
/in/foo.cc:41:30: error: 'endl' was not declared in this scope
  cout&lt;&lt;mul(a,b)&lt;&lt;endl;
                              ^~~~