wasm: Add new default lld switches to protect from stackoverflow overwriting global memory

[ryuukk]

I was stuck on trying to fix a bug on my code, whenever i was manipulating around large stucts, it'd change global data

I first thought of a memory corruption somewhere, but it turns out it was a stackoverflow issue!

Increasing the default stack (from 64kb) to 1mb fixed the issue... temporarily! as i was playing with more data, i hit the issue again.. so i looked around and found this PR on the zig repo: ziglang/zig#4496

Tada! now instead of overwritting my global memory, it throws a runtime error! that's better! i can now debug the issue properly!

Let's save people days of headache and make these options the default!

Zig/Rust also bumped the default stack size to 1mb (emscripten has a stack size of 5mb)

[PetarKirov]

It's failing with:

FAIL: LDC :: baremetal/wasm2.d (17 of 308)
******************** TEST 'LDC :: baremetal/wasm2.d' FAILED ********************
Script:
--
: 'RUN: at line 6';   /var/folders/wh/z5_y2cv53sg24tzvtw_f_y1m0000gn/T/build/bin/ldc2 -mtriple=wasm32-unknown-unknown-wasm -betterC -w /private/var/folders/wh/z5_y2cv53sg24tzvtw_f_y1m0000gn/T/cirrus-ci-build/tests/baremetal/wasm2.d -of=/private/var/folders/wh/z5_y2cv53sg24tzvtw_f_y1m0000gn/T/build/tests/baremetal/Output/wasm2.d.tmp.wasm
: 'RUN: at line 7';   /var/folders/wh/z5_y2cv53sg24tzvtw_f_y1m0000gn/T/build/bin/ldc2 -mtriple=wasm32-unknown-unknown-wasm -betterC -w -fvisibility=hidden /private/var/folders/wh/z5_y2cv53sg24tzvtw_f_y1m0000gn/T/cirrus-ci-build/tests/baremetal/wasm2.d -of=/private/var/folders/wh/z5_y2cv53sg24tzvtw_f_y1m0000gn/T/build/tests/baremetal/Output/wasm2.d.tmp_hidden.wasm
: 'RUN: at line 10';   grep myExportedFoo /private/var/folders/wh/z5_y2cv53sg24tzvtw_f_y1m0000gn/T/build/tests/baremetal/Output/wasm2.d.tmp.wasm
: 'RUN: at line 11';   grep myExportedFoo /private/var/folders/wh/z5_y2cv53sg24tzvtw_f_y1m0000gn/T/build/tests/baremetal/Output/wasm2.d.tmp_hidden.wasm
--
Exit Code: 1
Command Output (stdout):
--
$ ":" "RUN: at line 6"
$ "/var/folders/wh/z5_y2cv53sg24tzvtw_f_y1m0000gn/T/build/bin/ldc2" "-mtriple=wasm32-unknown-unknown-wasm" "-betterC" "-w" "/private/var/folders/wh/z5_y2cv53sg24tzvtw_f_y1m0000gn/T/cirrus-ci-build/tests/baremetal/wasm2.d" "-of=/private/var/folders/wh/z5_y2cv53sg24tzvtw_f_y1m0000gn/T/build/tests/baremetal/Output/wasm2.d.tmp.wasm"
# command stderr:
ldc2: Unknown command line argument '-z'.  Try: '/var/folders/wh/z5_y2cv53sg24tzvtw_f_y1m0000gn/T/build/bin/ldc2 --help'
ldc2: Did you mean '-D'?
ldc2: Unknown command line argument '--stack-first'.  Try: '/var/folders/wh/z5_y2cv53sg24tzvtw_f_y1m0000gn/T/build/bin/ldc2 --help'
ldc2: Did you mean '--help-list'?
error: command failed with exit status: 1

So most like you have to use a different syntax to set these options for WASM.

Also, I think it would be cleaner if you set the options in the config file here:

ldc/ldc2.conf.in

Lines 37 to 40 in 5a28329

	"^wasm(32|64)-":
	{
	switches = [
	"-defaultlib=",@WASM_DEFAULT_LDC_SWITCHES@

[ryuukk]

Also, I think it would be cleaner if you set the options in the config file here:

That was my initial thought, but i wasn't sure, i used these options in my dub file:

"lflags-ldc": [
    "-z","stack-size=1048576",
    "--stack-first",

    "-allow-undefined"
],

I'm not sure how to translate to use directly with LDC

[Geod24]

dub -v will give you the command line DUB is using. From a quick look, those are lflags, so you might want to use -L.

[JohanEngelen]

Also, I think it would be cleaner if you set the options in the config file here:

ldc/ldc2.conf.in

Lines 37 to 40 in 5a28329

	"^wasm(32|64)-":
	{
	switches = [
	"-defaultlib=",@WASM_DEFAULT_LDC_SWITCHES@

Indeed. The proposed change in the CMakeFile will only help if LDC is built with LLD built-in. The case where an external LLD is used for linking, would still need manual adding of these flags. If you add the flags to ldc/ldc2.conf.in directly, then that is solved.

Edit: or you add the flags unconditionally to the variable in CMakeFile. Perhaps better, because there are multiple ldc2.conf files that need adjustment (will be automatic when you change the CMakeFile variable).

[kinke]

or you add the flags unconditionally to the variable in CMakeFile. Perhaps better

Yep, exactly. [And prefixed with -L as mentioned by Mathias.]

[ryuukk]

it needs approval to trigger builds

[kinke]

Yeah that's annoying, and IIRC, requires a new approval after each push. - Wrt. making LDC specify these flags without integrated LLD too, please just move the new lines right before the if(LDC_WITH_LLD) block (without empty lines to make clear this contiguous CMake part is all about setting up WASM_DEFAULT_LDC_SWITCHES).

[ryuukk]

done!

[kinke]

without empty lines

Sorry about being so pedantic, but the CMake scripts are messy enough already. ;)

[ryuukk]

Sorry about that! done!

[kinke]

Thanks!