• d-bugmail puremagic.com (58/58) Nov 09 2022 https://issues.dlang.org/show_bug.cgi?id=23472

d-bugmail puremagic.com writes:

https://issues.dlang.org/show_bug.cgi?id=23472

          Issue ID: 23472
           Summary: scope(sucess) generate exception handling code.
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody puremagic.com
          Reporter: deadalnix gmail.com

See sample code:

char inc(string s, ref int i) {
    scope(success) i++;
    return s[i];
}

void main() {
    int i;
    inc("string", i);
}

The codegen using LDC is:
char example.inc(immutable(char)[], ref int):
        push    rbx
        mov     rbx, rdx
        movsxd  rcx, dword ptr [rdx]
        cmp     rdi, rcx
        jbe     .LBB0_1
        mov     al, byte ptr [rsi + rcx]
        add     ecx, 1
        mov     dword ptr [rbx], ecx
        pop     rbx
        ret
.LBB0_1:
        mov     r8, rdi
        lea     rsi, [rip + .L.str]
        mov     edi, 14
        mov     edx, 3
        call    _d_arraybounds_index PLT
        cmp     edx, 1
        jne     .LBB0_7
        mov     rdi, rax
        call    _d_eh_enter_catch PLT
        mov     rdi, rax
        call    _d_throw_exception PLT
.LBB0_7:
        add     dword ptr [rbx], 1
        mov     rdi, rax
        call    _Unwind_Resume PLT
        mov     rdi, rax
        call    _Unwind_Resume PLT

It contains exception handling code, which shouldn't be required for a
scope(success) statement, and in fact, we can see that the exception is caught
and rethrown immediately.

Checking with GDC and DMD shows that they also contain exception handling code,
so I assume this is being generated by the frontend.

--