[SOLVED] Make gcc warn about "jump to label crosses initialization of variable"

Issue

By default, gcc doesn't complain about jumping over variable initializations when compiling .c files, while it does when compiling .cpp files. I want it to complain when compiling c files. Is there an easy way to achieve this?

For example, the code below in .c does not produce any warnings/errors, while in .cpp it will:

int main()
{
        goto out;
        int i = 0;
out:
        return 0;
}

result:

gec@ubuntu:~/work/test/json_test$ gcc test.cpp -o test
test.cpp: In function ‘int main()’:
test.cpp:5:1: error: jump to label ‘out’ [-fpermissive]
 out:
 ^
test.cpp:3:7: note:   from here
  goto out;
       ^
test.cpp:4:6: note:   crosses initialization of ‘int i’
  int i = 0;
      ^

Solution

Use the -Wjump-misses-init option (or -Werror=jump-misses-init if you want it to be a hard error):

$ gcc -Wjump-misses-init try.c
try.c: In function 'main':
try.c:3:9: warning: jump skips variable initialization [-Wjump-misses-init]
         goto out;
         ^~~~
try.c:5:1: note: label 'out' defined here
 out:
 ^~~
try.c:4:13: note: 'i' declared here
         int i = 0;
             ^

Answered By - melpomene