[lxc-devel] [PATCH] update lua binding to support both 5.2 and 5.1

[Natanael Copa]

On Thu, 5 Sep 2013 09:41:12 -0400
Dwight Engen <dwight.engen at oracle.com> wrote:

> fix a bug in the parsing of /proc/mounts (from Natanael Copa
> <ncopa at alpinelinux.org>)
> 
> remove lxc subdir in cgroup paths
> 
> remove extraneous debug printfs
> 
> remove extra call to stats_clear
> 
> Tested lxc-top, and apitest.lua on both lua 5.1 and 5.2
> 
> Signed-off-by: Dwight Engen <dwight.engen at oracle.com>
> ---
>  configure.ac            | 10 +++++++++-
>  src/lua-lxc/Makefile.am |  4 ++--
>  src/lua-lxc/lxc.lua     | 50 ++++++++++++++++++++++---------------------------
>  src/lxc/lxc-top         | 14 ++++++++++----
>  4 files changed, 43 insertions(+), 35 deletions(-)
> 
> diff --git a/configure.ac b/configure.ac
> index df9a44b..f6f067d 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -164,9 +164,17 @@ AC_ARG_ENABLE([lua],
>  AM_CONDITIONAL([ENABLE_LUA], [test "x$enable_lua" = "xyes"])
>  
>  AM_COND_IF([ENABLE_LUA],
> -	[PKG_CHECK_MODULES([LUA], [$LUAPKGCONFIG >= 5.1],[],[AC_MSG_ERROR([You must install lua-devel for lua 5.1])])
> +	[AC_CHECK_PROG([LUA],[lua],[lua],[no])
> +	PKG_CHECK_MODULES([LUADEVEL], [$LUAPKGCONFIG >= 5.1],[],[AC_MSG_ERROR([You must install lua-devel])])
>  	AC_DEFINE_UNQUOTED([ENABLE_LUA], 1, [Lua is available])])
>  
> +AS_IF([test "x$LUA" != "xno"],
> +	[AC_MSG_CHECKING([for lua version])
> +	LUA_VERSION=`$LUA -e 'print(_VERSION)' | awk '{print $2}'`
> +	AC_MSG_RESULT([$LUA_VERSION])
> +	AC_SUBST([LUA_VERSION])])
> +
> +
>  # Optional test binaries
>  AC_ARG_ENABLE([tests],
>  	[AC_HELP_STRING([--enable-tests], [build test/example binaries])],

What if you have both lua 5.1 and 5.2 installed (eg debian/ubuntu) and
want build against lua 5.1? On Ubuntu I get:

lua -e 'print(_VERSION)' | awk '{print $2}'
5.2

but i might want use the lua5.1.pc

And what happens if you cross-compile? (cross-compiling is a new can of
worms that i don't think we should worry too much about)

This is why i dropped the idea of running lua binary and try to rely on
pkg-config info only.

Even if fedora does not provide INSTALL_[CL]MOD it provides V:
[ncopa at localhost ~]$ uname -a
Linux localhost.localdomain 3.9.5-301.fc19.x86_64 #1 SMP Tue Jun 11 19:39:38 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
[ncopa at localhost ~]$ pkg-config --variable V lua
5.1

We can fallback to this in case INSTALL_[CL]MOD is missing.

INSTALL_[CL]MOD appears to be available on Ubuntu(/Debian?), Arch Linux
and Alpine Linux. Suse I don't know.



> diff --git a/src/lxc/lxc-top b/src/lxc/lxc-top
> index 31aaecf..969f1f7 100755
> --- a/src/lxc/lxc-top
> +++ b/src/lxc/lxc-top
> @@ -97,9 +97,16 @@ end
>  
>  function usleep(n)
>      if (n ~= 0) then
> -	ret = os.execute("usleep " .. tonumber(n))
> -	if (ret ~= 0) then
> -	    os.exit(0)
> +	local ret = os.execute("usleep " .. tonumber(n))
> +	if (string.sub(_VERSION, 5) == "5.2") then
> +	    if (ret == nil) then
> +		os.exit(0)
> +	    end
> +	end
> +	if (string.sub(_VERSION, 5) == "5.1") then
> +	    if (ret ~= 0) then
> +		os.exit(0)
> +	    end
>  	end
>      end
>  end

How about implement a tiny usleep in core in C instead:

diff --git a/src/lua-lxc/core.c b/src/lua-lxc/core.c
index d404707..504e147 100644
--- a/src/lua-lxc/core.c
+++ b/src/lua-lxc/core.c
@@ -27,11 +27,13 @@
 #include <lauxlib.h>
 #include <assert.h>
 #include <string.h>
+#include <unistd.h>
 #include <lxc/lxccontainer.h>
 
 #if LUA_VERSION_NUM < 502
 #define luaL_newlib(L,l) (lua_newtable(L), luaL_register(L,NULL,l))
 #define luaL_setfuncs(L,l,n) (assert(n==0), luaL_register(L,NULL,l))
+#define luaL_checkunsigned(L,n) luaL_checknumber(L,n)
 #endif
 
 #ifdef NO_CHECK_UDATA
@@ -379,10 +381,17 @@ static int lxc_default_config_path_get(lua_State *L) {
     return 1;
 }
 
+/* utility functions */
+static int lxc_util_usleep(lua_State *L) {
+    usleep((useconds_t)luaL_checkunsigned(L, 1));
+    return 0;
+}
+
 static luaL_Reg lxc_lib_methods[] = {
     {"version_get",            lxc_version_get},
     {"default_config_path_get",        lxc_default_config_path_get},
     {"container_new",          container_new},
+    {"usleep",                 lxc_util_usleep},
     {NULL, NULL}
 };
 
diff --git a/src/lxc/lxc-top b/src/lxc/lxc-top
index 31aaecf..8e8bafb 100755
--- a/src/lxc/lxc-top
+++ b/src/lxc/lxc-top
@@ -22,6 +22,7 @@
 --
 
 local lxc    = require("lxc")
+local core   = require("lxc.core")
 local getopt = require("alt_getopt")
 local lfs    = require("lfs")
 
@@ -95,15 +96,6 @@ function strsisize(size, width)
     return string.format("%3d.00   ", size)
 end
 
-function usleep(n)
-    if (n ~= 0) then
-       ret = os.execute("usleep " .. tonumber(n))
-       if (ret ~= 0) then
-           os.exit(0)
-       end
-    end
-end
-
 function tty_lines()
     local rows = 25
     local f = assert(io.popen("stty -a | head -n 1"))
@@ -238,5 +230,5 @@ do
     end
     stats_print(string.format("TOTAL (%-2d)", #containers), stats_total)
     io.flush()
-    usleep(optarg["d"] * 1000000)
+    core.usleep(optarg["d"] * 1000000)
 end