lab1_challenge1 打印用户程序调用栈(难度:★★☆☆☆)给定应用12345678910111213141516171819202122232425* user/app_print_backtrace.c 1 /\* 2 \* Below is the given application for lab1_challenge1_backtrace. 3 \* This app prints all functions before calling print_backtrace(). 4 \*/ 5 6 #include "user_lib.h&qu