Eliminate unwind tables?

[TurkeyMan]

There's no -fno-unwind-tables I can find. My binaries are loaded with .eh_frame symbols.
I need to reliably eliminate all exception related bloat, what's the proper thing to do?

[QuantumSegfault]

Try --fno-exceptions

[TurkeyMan]

--fno-exceptions breaks ctfe... so it's basically useless. I didn't see if that trims the tables or not, because it's impossible to compile ;)
I was tinkering with things like --emit-dwarf-unwind, something else I found that I tinkered with too, can't remember.

[TurkeyMan]

I can probably rework all my ctfe code, but that's a massive hassle :/

[dkorpel]

Even with disabled exceptions you still get .eh_frame. I personally use this discard_eh.ld script:

SECTIONS { /DISCARD/ : { *(.eh_frame) *(.eh_frame_hdr) *(.sframe) } }
INSERT AFTER .text;

Passed to LDC with: -L--script=discard_eh.ld

[thewilsonator]

--emit-dwarf-unwind=<value>  - Whether to emit DWARF EH frame entries.
    =always                  -   Always emit EH frame entries
    =no-compact-unwind       -   Only emit EH frame entries when compact unwind is not available
    =dwarf-only              -   Force compact unwind to reference DWARF
    =default                 -   Use target platform default

looks to be what you want here.

[TurkeyMan]

@dkorpel Indeed, I've been using linker script to discard the section, but it's not really nice, especially when you include windows/MS tools, etc.
@thewilsonator That was the first thing I tinkered with. I didn't succeed.

Anyway, I think there's something to think about here.
1, exceptions should remain valid in CTFE even if you disable them
2, if i do disable them completely, then there's no reason to find .eh_frame in the binary, that seems like a bug
3, dwarf has its own material in addition to .eh_frame material.

Basically, when this stuff is disabled and unreferenced by the binary, it should be suppressed from the binary.

I have a workaround, but I'd love to remove it.

[kinke]

Should be trivial to add in

ldc/gen/abi/abi.cpp

Lines 170 to 175 in f364c1c

	void TargetABI::setUnwindTableKind(llvm::Function *fn) {
	llvm::UWTableKind kind = defaultUnwindTableKind();
	if (kind != llvm::UWTableKind::None) {
	fn->setUWTableKind(kind);
	}
	}

if i do disable them completely, then there's no reason to find .eh_frame in the binary, that seems like a bug

No, then clang wouldn't have/need a -fno-unwind-tables either. The tables are e.g. mandated by the x86_64 SysV ABI IIRC.