WASM backend browser issue

[SewerynKaminski]

Describe the bug

Command

$ v -no-bounds-checking -enable-globals -b wasm -os browser test.wasm.v
or
$ v -no-bounds-checking -b wasm -os browser test.wasm.v

give me an error
wasm error: wasm.expr_stmt(): unhandled node: v.ast.EmptyStmt

no wasm binary output

   $ cat test.wasm.v
   pub main(){}

Reproduction Steps

$ echo "pub main(){}" > test.wasm.v
$ v -no-bounds-checking -enable-globals -b wasm -os browser test.wasm.v

Expected Behavior

Generate wasm binary for browser target.

Current Behavior

Generate an error
wasm error: wasm.expr_stmt(): unhandled node: v.ast.EmptyStmt
Gives no wasm binary

Possible Solution

none

Additional Information/Context

In V ver. 0.4.7 works fine

V version

V 0.5.1 28fb4e6

Environment details (OS name and version, etc.)

V full version	V 0.5.1 28fb4e6
OS	linux, Ubuntu 25.04
Processor	16 cpus, 64bit, little endian, AMD Ryzen 7 3700X 8-Core Processor
Memory	0.36GB/15.06GB
V executable	/home/seven/vlang/v/v
V last modified time	2026-04-05 14:09:25
V home dir	OK, value: /home/seven/vlang/v
VMODULES	OK, value: /home/seven/.vmodules
VTMP	OK, value: /tmp/v_1000
Current working dir	OK, value: /home/seven/programy/v_wasm/mem
Git version	git version 2.48.1
V git status	weekly.2024.31-3979-g28fb4e6d
.git/config present	true
cc version	cc (Ubuntu 14.2.0-19ubuntu2) 14.2.0
gcc version	gcc (Ubuntu 14.2.0-19ubuntu2) 14.2.0
clang version	Ubuntu clang version 20.1.2 (0ubuntu1)
tcc version	tcc version 0.9.28rc 2025-02-13 HEAD@f8bd136d (x86_64 Linux)
tcc git status	thirdparty-linux-amd64 696c1d84
emcc version	N/A
glibc version	ldd (Ubuntu GLIBC 2.41-6ubuntu1.2) 2.41

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[JalonSolov]

An empty main() is basically no program at all, so why even bother? Looks to me like the compiler is telling you that you didn't need to run it at all - which seems correct.

[SewerynKaminski]

@JalonSolov you can put watever you want in to main() the error stay the same. In my Issue I presented the minimal exapmple.

[JalonSolov]

Ok, I tried with an existing example:

$ v -no-bounds-checking -enable-globals -b wasm -os browser examples/hello_world.v
wasm error: wasm.expr_stmt(): unhandled node: v.ast.EmptyStmt
$

So yes, it's happening with other things. You didn't say it happened with everything in your initial report, but I confirmed that it is happening with others.

However, this does work:

$ v -b wasm examples/hello_world.v
$

So some combination of the options you used it causing V to hit the problem.

N.B. The WASM backend is still very much WIP, so don't expect many things to work. The examples under examples/wasm do, but only if you compile with no extra options other than -b wasm, or any others mentioned in README files alongside the examples (like examples/wasm/mandelbrot).

[SewerynKaminski]

@JalonSolov thanks to confirm :)
The -os browser flag generate propper wasm binary in V(0.4.7) but not in V (0.5.1) may be some regression bug?