segmentation fault when running clang built wasm

[xyproto]

When running wac on sha1sum.wasm from the vmir project, I get the following error:

./wac ~/clones/vmir/examples/prebuilt/sha1sum.wasm
zsh: segmentation fault (core dumped)  ./wac ~/clones/vmir/examples/prebuilt/sha1sum.wasm

I'm using:

• latest master of wac, commit 1197a2d
• 64-bit Arch Linux with the official gcc package (gcc 8.1.1)
• lib32-libedit from AUR

When compiling with -O1 -g and using bt full in gdb, this is the output:

(gdb) r ~/clones/vmir/examples/prebuilt/sha1sum.wasm
Starting program: /home/afr/clones/wac/wac ~/clones/vmir/examples/prebuilt/sha1sum.wasm

Program received signal SIGSEGV, Segmentation fault.
0xf7dae279 in __memset_sse2 () from /usr/lib32/libc.so.6
(gdb) bt full
#0  0xf7dae279 in __memset_sse2 () from /usr/lib32/libc.so.6
No symbol table info available.
#1  0x565655b0 in thunk_out_i_iii (m=0xf7b2d010, function=0x5658b2b8, type=0x5658a6dc) at thunks.c:454
        res = <optimized out>
#2  0x5655fc11 in thunk_out (m=0xf7b2d010, fidx=2) at wa.c:544
        func = 0x5658b2b8
        type = 0x5658a6dc
        thunk_mask = 8454417
        p = <optimized out>
#3  0x565601e3 in interpret (m=0xf7b2d010) at wa.c:809
        block = <optimized out>
        prev_pages = <optimized out>
        sval = <optimized out>
        didx = <optimized out>
        delta = <optimized out>
        bytes = 0xf7fd0000 ""
        stack = 0xf7b2d074
        cur_pc = 492
        block = <optimized out>
        arg = <optimized out>
        val = <optimized out>
        fidx = <optimized out>
        tidx = <optimized out>
        cond = <optimized out>
        depth = <optimized out>
        count = <optimized out>
        flags = <optimized out>
        offset = <optimized out>
        addr = <optimized out>
        maddr = <optimized out>
        mem_end = <optimized out>
        depths = <optimized out>
        opcode = 16 '\020'
        a = <optimized out>
        b = <optimized out>
        c = 4294967104
        d = <optimized out>
        e = <optimized out>
        f = 6221221224307818496
        g = <optimized out>
        h = <optimized out>
        i = -1.03310949e+34
        j = <optimized out>
        k = <optimized out>
        l = 1.3447704791445071e-313
        overflow = false
#4  0x56563be8 in invoke (m=0xf7b2d010, entry=<optimized out>, argc=-1, argv=0xffffd0c0) at wa.c:1997
        fidx = 6
        type = 0x5658a6a0
        result = <optimized out>
#5  0x5655eec7 in main (argc=<optimized out>, argv=<optimized out>) at wac.c:63
        mod_path = <optimized out>
        entry = <optimized out>
        line = <optimized out>
        repl = 0
        debug = 0
        res = 0
        option_index = 0
        c = <optimized out>
        long_options = {{name = 0x5657545c "repl", has_arg = 0, flag = 0xffffcfac, val = 1}, {name = 0x56575461 "debug", has_arg = 0, flag = 0xffffcfb0, val = 1}, {name = 0x0, has_arg = 0, flag = 0x0, val = 0}}
        opts = {disable_memory_bounds = false, mangle_table_index = false, dlsym_trim_underscore = false}
        m = <optimized out>
(gdb)

The problematic line could be line 454 in thunks.c?

[kanaka]

I suspect the linkage isn't setup the way wac/wace is expecting so the libc memset is being called with an invalid pointer. I've only tested C programs built the way I describe in the README.md (using a recent version of binaryen and emscripten). I.e. like this:

emcc $(CFLAGS) -s WASM=1 -s SIDE_MODULE=1 -s LEGALIZE_JS_FFI=0 prog.c -o prog.wasm

The prebuilt sha1sum.wasm file in vmir was built using clang/llvm via LLVM IR form. I would actually have been surprised if that worked without tweaks. It's probably something that we want to get working although I won't have time to work on this any time in the near future although I would be happy to take a pull request and answer specific questions about why wac/wace work the way they do.

[xyproto]

Ok, thanks for the response. :)