about "fix lr causes the call stack inaccurate"

[ZhiyuWong]

#327 Stop collect link register may cause the lack of second frame of backtrace.

The Procedure Call Standard for the ARM 64-bit Architecture indicate that lr stored

sequentially next value of program counter—the return address

so, the instruction before address stored in link register is the call instruction, which is the second frame of backtrace.

5.3 Subroutine Calls
The A64 instruction set contains primitive subroutine call instructions, BL and BLR, which performs a branch-with link operation. The effect of executing BL is to transfer the sequentially next value of the program counter—the return address—into the link register (LR) and the destination address into the program counter. The effect of executing BLR is similar except that the new PC value is read from the specified register.

[ZhiyuWong]

Here's an example

void test1() {
    char *a = (char *)0x1;
    *a = 1;
}

void test() {
    test1();
}

When we call test() from -[ViewController oneClickCrash:], the process will crash and the crash log is list below
Enable link register collecting:

Thread 0 Crashed:
0   Demo                0x00000001027f56d0 test1 + 20
1   Demo                0x00000001027f56e8 test + 12
2   Demo                0x00000001027f571c -[ViewController oneClickCrash:] + 44
...

Disable link register collecting:

Thread 0 Crashed:
0   Demo                0x000000010224171c test1 + 20
1   Demo                0x0000000102241768 -[ViewController oneClickCrash:] + 44
...

[JunyiXie]

I think
We can't control the behavior of the compiler, we should not consider the case and use the lr register.