Zig Version

0.15.0-dev.99+c1db72cdb

Steps to Reproduce and Observed Behavior

Tried finding existing reports or similar issues, but no luck. Apologies if there's an existing one I couldn't find.

Found while trying to build dvui for wasm32-freestanding in ReleaseSafe mode, which fails, but which works in Debug mode. The smallest reproducible snippet I could find is

// test.zig
export fn bla(f: i32) f64 {
    return @exp2(@as(f64, @floatFromInt(f)));
}

Then

$ zig build-exe -target wasm32-freestanding -O Debug -fno-entry -rdynamic test.zig 
$ echo $?
0
$ zig-0.15.0-dev build-exe -target wasm32-freestanding -O ReleaseSafe -fno-entry -rdynamic test.zig 
error: wasm-ld: test.wasm.o: undefined symbol: ldexp

Changing the argument from i32 to i64 makes it pass:

export fn bla(f: i64) f64 {
    return @exp2(@as(f64, @floatFromInt(f)));
}

Changing the integer to i32 argument and the floats to f32 makes it fail on undefined symbol: ldexpf.

Expected Behavior

I expected a build which succeeds in Debug to also succeed in any of the release build modes.