[vlc-devel] [PATCH] configure: detect 32/64-bit lua 5.3 bytecode

[Steve Lhomme]

On Fri, Apr 8, 2016 at 1:27 AM, Andrey Gursky <andrey.gursky at e-mail.ua> wrote:
> The ABI magic bytes in lua 5.3 bytecode are located at a different
> offset than in lua 5.1 or lua 5.2 bytecode. This patch fixes the
> detection by distinguishing two cases for <5.3 and 5.3 lua versions.
>
> For documentation purposes:
>
> lua version can be obtained at the offset 4 (e.g. 0051, 0053).
> ABI magic bytes (32-bit: 0404) can be obtained:
>  - lua 5.1 and 5.2: at the offset 8;
>  - lua 5.3: at the offset 12.
>
> $ echo | luac -o - - | od -j 0 -N 100 -t x2
>
> luac5.1 32-bit:
> 0000000 4c1b 6175 0051 0401 0404 0008 0007 0000
> 0000020 733d 6474 6e69 0000 0000 0000 0000 0000
> 0000040 0200 0102 0000 1e00 8000 0000 0000 0000
> 0000060 0000 0100 0000 0100 0000 0000 0000 0000
> 0000100 0000 0000
>
> luac5.1 64-bit:
> 0000000 4c1b 6175 0051 0401 0408 0008 0007 0000
> 0000020 0000 0000 733d 6474 6e69 0000 0000 0000
> 0000040 0000 0000 0200 0102 0000 1e00 8000 0000
> 0000060 0000 0000 0000 0100 0000 0100 0000 0000
> 0000100 0000 0000 0000 0000
>
> luac5.3 32-bit:
> 0000000 4c1b 6175 0053 9319 0a0d 0a1a 0404 0804
> 0000020 7808 0056 0000 0000 0000 0000 0000 7728
> 0000040 0140 3d07 7473 6964 006e 0000 0000 0000
> 0000060 0000 0201 0001 0000 0026 0080 0000 0000
> 0000100 0001 0000 0001 0000 0000 0001 0000 0001
> 0000120 0000 0000 0000 0001 0000 5f05 4e45 0056

I get different things on Windows with 5.3 32 bits. When luac produces
a file it gives the same result. But when outputting to stdout it
produces different data.

$ echo|luac - && od -j 0 -N 16 -t x2 luac.out
0000000 4c1b 6175 0053 9319 0a0d 0a1a 0404 0804

$ echo|luac -o - -|od -j 0 -N 16 -t x2
0000000 4c1b 6175 0053 9319 0d0d 1a0a 0a0d 0404

Anyone has similar result on other platorms ?



> luac5.3 64-bit:
> 0000000 4c1b 6175 0053 9319 0a0d 0a1a 0804 0804
> 0000020 7808 0056 0000 0000 0000 0000 0000 7728
> 0000040 0140 3d07 7473 6964 006e 0000 0000 0000
> 0000060 0000 0201 0001 0000 0026 0080 0000 0000
> 0000100 0001 0000 0001 0000 0000 0001 0000 0001
> 0000120 0000 0000 0000 0001 0000 5f05 4e45 0056
> ---
>  configure.ac | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/configure.ac b/configure.ac
> index 1842021..5eb0a47 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -1554,8 +1554,12 @@ then
>    AS_IF([test "${LUAC}" = "false"], [
>      AC_MSG_ERROR([Could not find the LUA byte compiler.])
>    ])
> -  AS_IF([test -d "${CONTRIB_DIR}" -a -f "${CONTRIB_DIR}/lib/liblua.a" -a `echo|${LUAC} -o - -|od -j 8 -N 2 -t x2|head -n 1|tr -s ' '|cut -d' ' -f2` != 0404], [
> -    AC_MSG_ERROR([You need 32-bits luac when using lua from contrib.])
> +  AS_IF([test -d "${CONTRIB_DIR}" -a -f "${CONTRIB_DIR}/lib/liblua.a"], [
> +    lua_ver=`echo|${LUAC} -o - -|od -j 4 -N 2 -t x2|head -n 1|tr -s ' '|cut -d' ' -f2`
> +    AS_IF([test ${lua_ver} -lt 53], [lua_abi_offset=8], [lua_abi_offset=12])
> +    AS_IF([test `echo|${LUAC} -o - -|od -j ${lua_abi_offset} -N 2 -t x2|head -n 1|tr -s ' '|cut -d' ' -f2` != "0404"], [
> +      AC_MSG_ERROR([You need 32-bits luac when using lua from contrib.])
> +    ])
>    ])
>  fi
>  AM_CONDITIONAL(BUILD_LUA, [test "${have_lua}" = "yes"])
> --
> 2.7.4
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