Re: Compile error for struct on OS-X

[Philipp Janda <siffiejoe@...>]

Am 30.03.2016 um 01:46 schröbte Dan Christian:
> I'm trying to install struct on OS-X (10.11), and am getting compile
> errors.  I'm new to Lua, so I might be missing something obvious.  The
> details are at the end:
>
> I have Lua51 installed via macports, along with luarocks.  I'll
> primarily be using it with luajit.

You are not using Lua 5.1 at the moment. You are using Lua 5.3. See below.

> Anybody have this working?
>
> Is there a way to get luarocks to use gcc?

Yes, you can append the CC and LD variables to your LuaRocks incantation:

    luarocks install struct CC='env MACOSX_DEPLOYMENT_TARGET=10.8 gcc' 
LD='env MACOSX_DEPLOYMENT_TARGET=10.8 gcc'

(you can also add those to your config file to make them permanent.)

> Where would I send a bug?

This list is usually a good start if you don't know a better place.

> Thanks,
>
> Dan
>
>
> sudo luarocks install struct
>
> Installing https://luarocks.org/struct-1.2-2.src.rock...

This version is pretty old. The latest version available on LuaRocks is 
1.4-1, but that version specifies that it is only compatible with Lua >= 
5.1 and < 5.3. Since this later version isn't chosen, we can deduce that 
LuaRocks assumes that you don't have Lua 5.1 or 5.2 installed. The old 
1.2-1 version *should* have specified that it is only compatible with 
Lua 5.1, but back in the day folks were overly optimistic about 
compatibility with future Lua versions.

> Using https://luarocks.org/struct-1.2-2.src.rock... switching to 'build' mode
>
> env MACOSX_DEPLOYMENT_TARGET=10.8 /usr/bin/clang -O2 -fPIC
> -I/opt/local/include -c struct.c -o struct.o
>
> struct.c:181:27: warning: implicit declaration of function
> 'luaL_putchar' is invalid in C99 [-Wimplicit-function-declaration]
>
>      while (toalign-- > 0) luaL_putchar(&b, '\0');
>
>                            ^

`luaL_putchar` was a thing in Lua 5.0. Lua 5.1 still had it for 
compatibility. Lua 5.2 and 5.3 don't have that function/macro anymore. 
Did I mention that the struct-1.2-2 version is pretty old?!

> struct.c:318:37: error: array has incomplete element type 'const
> struct luaL_reg'
>
> static const struct luaL_reg thislib[] = {
>
>                                      ^

`luaL_reg` was renamed to `luaL_Reg` in Lua 5.1 (which also supported 
the old name for compatiblity). Lua 5.2 and 5.3 don't.

> struct.c:318:21: note: forward declaration of 'struct luaL_reg'
>
> static const struct luaL_reg thislib[] = {
>
>                      ^
>
> struct.c:326:3: warning: implicit declaration of function
> 'luaL_register' is invalid in C99 [-Wimplicit-function-declaration]
>
>    luaL_register(L, "struct", thislib);
>
>    ^

`luaL_register` is deprecated (but available) in Lua 5.2, and gone by 
default in Lua 5.3.

> 2 warnings and 1 error generated.
>
>
> Error: Build error: Failed compiling object struct.o


I've attached a new rockspec that works[*] for Lua 5.3. Download it and 
use it like this:

    luarocks install struct-1.4-2.rockspec

Lua 5.3 has string (un)packing built-in, btw. Alternatively you can 
really install Lua 5.1 and configure LuaRocks to use that version.

HTH,
Philipp


  [*]: Builds at least. The code is the same as for version 1.4-1, but 
the test script asserts on my machine for Lua 5.1, 5.2, and 5.3.


package="struct"
version="1.4-2"
source = {
   url = "http://www.inf.puc-rio.br/~roberto/struct/struct-0.2.tar.gz";,
   dir = ".",
}
description = {
   summary = "A library to convert Lua values to and from C structs",
   detailed = [[
      This library offers basic facilities to convert Lua values to and
      from C structs. Its main functions are struct.pack, which packs
      multiple Lua values into a struct-like string; and struct.unpack,
      which unpacks multiple Lua values from a given struct-like string. 
   ]],
   homepage = "http://www.inf.puc-rio.br/~roberto/struct/";,
   license = "MIT/X"
}
dependencies = {
   "lua >= 5.1, <= 5.3"
}
build = {
   type = "builtin",
   modules = {
      struct = {
         "struct.c",
      }
   },
}