Several failures with wasm targets and cc/c++ toolchains (and problems with lto)

[KaruroChori]

Zig Version

0.14.0-dev.2851+b074fb7dd

Steps to Reproduce and Observed Behavior

Very simple c++ file:

#include <iostream>

int main(){
	std::cout<<"hello\n";
	return 0;
}

And a c one:

#include <stdio.h>

int main(){
	printf("hello\n");
	return 0;
}

Running the following commands, result on the right:

zig c++ --target=wasm32-wasi main.cpp -flto -> fail to run
zig c++ --target=wasm32-wasi main.cpp -> fail, surprisingly as from meson it works.
zig cc --target=wasm32-wasi main.c -flto -> fail to run
zig cc --target=wasm32-wasi main.c -> working

I also tested the C++ cases using the C code, so no libc++ and it works without -flto.
For failure, I mean that running it via a wasm/wasi runtime like bun, it results in an exception from the runtime.

I also noticed that the -static attribute does not work, so zig cc main.c -static does not generate a static build, but clang would.

Expected Behavior

All the previous cases should just compile and run fine.
So, running bun run a.out should just display hello for each of the test cases.
Further problems and discussion @ lazy-eggplant/vs.templ#18 where some of these issues were first isolated.

[nektro]

could be related that zig cc expects a single hyphen -target

[KaruroChori]

Does it? If using a single one it returns

error: Unknown Clang option: '-target=wasm32-wasi'

[alexrp]

Please include more details in the issue description on how the examples fail.

[alexrp]

Does it? If using a single one it returns

error: Unknown Clang option: '-target=wasm32-wasi'

Should be a space instead of =.

[jedisct1]

$ cat > a.c << EOT
#include <stdio.h>

int main(void) {
	puts("hello");
	return 0;
}
EOT

$ zig cc -target wasm32-wasi -Os -flto a.c -o a.wasm

$ wasmer run a.wasm
hello

[jedisct1]

OP seems to be testing using bun and I guess "fails to run" means that Bun prints RuntimeError: Out of bounds memory access (evaluating 'instance.exports').

bun run a.wasm triggers that error, with or without -flto.

Whereas a Hello World in Zig works just fine in Bun unless link_libc is set. When link_libc is set, we also get RuntimeError: Out of bounds memory access (evaluating 'instance.exports') from Bun.

So, there's something horrible in wasi-libc that Bun doesn't like. Random guess: Bun doesn't set __heap_end.

[KaruroChori]

@alexrp I adjusted the issue to cover what I meant by failure. As for -target x or --target=x, they work interchangeably for all the test cases I introduced before.

@jedisct1 in your example is -Os causing it to fail, in addition to enabling the LTOs. Surprisingly, without optimizations of any kind it works in bun.