Revision a4c81e1c-f0b1-43be-9ad3-5edf4b7acbad - Code Golf Stack Exchange

# [C (gcc)], 62 bytes

<!-- language-all: lang-c -->

 f(a,b)char*a,*b;{for(;*a&*b;)putchar(*a++^*b++);puts(*a?a:b);}

[Try it online!][TIO-kcqz8o81]

[C (gcc)]: https://gcc.gnu.org/
[TIO-kcqz8o81]: https://tio.run/##jVHbToNAEH33K1YSdbkYaa1aRW1q28QHE3uJ6YNUXWBREgQETIkN344zu1DbPrnJMGdmZ86ZZdzjd9etKp8yw1HdD5ZqzNAca@XHKbU0dghYTb5zvKEa0/UXzdF11YJUBnGPXTmqVVafLIioSlZ7BI5gITnP8lf2vCA3ZKXc8zCMDcUgEiFgjutxBGG85KnLMhFgF/pW@7RztpNAZ7bw@@bibWntyjm13DxOQ28fK5eP04ehbARGBJe9IyIOBiLRvTjfkurfDYYjBF9ZDSaTv5m2VHmR8CLnXq1rFy3fLkwGnoM3wRwwD7t72i3RBdlsMhd8T@PxaDroz0ab4lDelRRmB6yNNAqRF@amYXGSJHJAOXI9GqyO0CDKSRB5vIDBTKuG1yQLfnjs02Zu9aROiOeoFtF1UdmsEk@SApdPFVs5yGwQk96OANY7Fi0Lo9mBDFVrzeDTfxY2UiCA9Ou/u1VY7pXVLw "C (gcc) – Try It Online"