This should get past the issue of code bracketed between comments
sed -E '/^\s*\/\*/!bx ; /\*\/\s*$/!bx ; /\*\/[^;]+.*\/\*/bx ; d; :x'
If a line doesn't start with a comment marker led only by whitespace then it starts with code so branch past the delete to x
/^\s*\/\*/!bx
If the line starting as a comment doesn't end as a comment followed only by whitespace then there is code at the end so branch past the delete to x
/\*\/\s*$/!bx
If the comment line contains a (second) comment end followed by statement ; and eventually by another comment start then there is code inside so branch past the delete to x
/\*\/[^;]+.*\/\*/bx
Since we found no code then delete
d
Otherwise finish without doing anything
x
Tested on
/* Comment 1 */
printf("It is /* Comment 2 */\n");
x = 5; /* Comment 3 */
/* Comment 4 */
/* Comment 5 */ y = 0;
/*
* Comment 6
*/
// Comment 7
/* between two comments */ x = 0; /* could be some code */
Output is
printf("It is /* Comment 2 */\n");
x = 5; /* Comment 3 */
/* Comment 5 */ y = 0;
/*
* Comment 6
*/
// Comment 7
/* between two comments */ x = 0; /* could be some code */