**Answer**\n\nThe crash isn’t caused by the loop itself – it’s caused by calling `fgets` without a proper prototype. \nIf you forget to `#include \u003cstdio.h\u003e` (or otherwise declare the function)， the compiler assumes that `fgets` returns an `int`. \nWhen the program actually calls the real `fgets` (which returns a `char *`)， the return value is interpreted incorrectly， the loop condition becomes undefined， and the program can crash.\n\n**Fix**\n\n```c\n#include \u003cstdio.h\u003e /* ← add this */\n\nint main(void)\n{\n char buffer[1024]；\n while (fgets(buffer， sizeof buffer， stdin) != NULL) {\n /* …process buffer… */\n }\n return 0；\n}\n```\n\nMake sure you include `\u003cstdio.h\u003e` (or provide the correct prototype) before using `fgets`. This eliminates the mismatch and stops the crash.。