luabind

Am Dienstag, den 09.08.2011, 07:17 -0700 schrieb Josh Stratton:
> so I'm assuming there is some error in there
> I thought should raise an exception.

Nope, errors don't usually raise exceptions, they just change the return
value. Read the manual regarding luaL_dostring(), I don't know how to
check its success off the top of my head.

On 9 August 2011 15:43, Willi Schinmeyer <willi@...> wrote:

> Am Dienstag, den 09.08.2011, 07:17 -0700 schrieb Josh Stratton:
> > so I'm assuming there is some error in there
> > I thought should raise an exception.
>
> Nope, errors don't usually raise exceptions, they just change the return
> value. Read the manual regarding luaL_dostring(), I don't know how to
> check its success off the top of my head.
>
>
>
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luaL_dostring [1] is really a macro which calls two functions in Lua 5.1, it
simply calls luaL_loadstring [2] then lua_pcall [3] if there was not an
error. The macro is an "logical or" of both function return values and
therefore luaL_dostring as such "returns" a result, either it is 0 for
success or 1 for error. Using luaL_dostring looses information of the error
category in the form of a int which is returned by either of the function
yet the function which errors also puts a message on the top of the stack.
You therefore can check the return value of luaL_dostring and get the error
from the top of the stack but I always advise that people should at least
call these two functions yourself or use a function which replaces
luaL_dostring
functionality, from there you can throw a typed none generic exception using
the int return value from the failing function if you wish [4] :)


[1] http://www.lua.org/manual/5.1/manual.html#luaL_dostring
[2] http://www.lua.org/manual/5.1/manual.html#luaL_loadstring
[3] http://www.lua.org/manual/5.1/manual.html#lua_pcall
[4]
http://code.google.com/p/oolua/source/browse/trunk/src/oolua_check_result.cpp


Liam

On Aug 09, 2011 7:17 AM, Josh Stratton wrote:
> I'm trying to get error messages to display and I was following this
> tutorial.  However, I can't seem to get any error exceptions.  In a
> lua script I'm running, I have a print at the top and bottom and it's
> only hitting the top one, so I'm assuming there is some error in there
> I thought should raise an exception.
>
> http://www.nuclex.org/articles/5-cxx/1-quick-introduction-to-luabind
>
> void loadLuaFile(lua_State* state, QString fileName)
> {
>      QFile file(fileName);
>      file.open(QIODevice::ReadOnly);
>      QString lines = file.readAll();
>      //std://:cout<<;  lines.toStdString()<<  std::endl;
>      try {
>          std::cout<<  "executing "<<  fileName.toStdString()<<
> "...\n-----------"<<  std::endl;
>          std::cout<<  lines.toStdString().c_str()<<  std::endl;
>          luaL_dostring(state, lines.toStdString().c_str());
>      } catch (const std::exception&TheError) {
>          std::cout<<  "*"<<  std::endl;
>          std::cout<<  TheError.what()<<  std::endl;
>      }
>
>      file.close();
> }
>
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Luabind only throws exceptions if you call into Lua code *through* 
Luabind. You're calling Lua code through the standard Lua API, therefore 
no exceptions will be thrown. Instead, the typical Lua error handling 
code will be used.

On Wed, August 10, 2011 12:43 am, Willi Schinmeyer wrote:


	> Am Dienstag, den 09.08.2011, 07:17 -0700 schrieb Josh Stratton:

	>> so I'm assuming there is some error in there

	>> I thought should raise an exception.

	>

	> Nope, errors don't usually raise exceptions, they just change
the return

	> value. Read the manual regarding luaL_dostring(), I don't know
how to

	> check its success off the top of my head.

	


	



	luaL_dostring reurns 1 on error, and in that case you should find a
string describing the problem at the top of the Lua stack.


	Nigel

Thanks for the responses.  What is the corresponding luabind call
similar to luaL_dostring that actually throws exceptions?

On Tue, Aug 9, 2011 at 3:22 PM, Nigel Atkinson <nigel@...> wrote:
> On Wed, August 10, 2011 12:43 am, Willi Schinmeyer wrote:
>
>> Am Dienstag, den 09.08.2011, 07:17 -0700 schrieb Josh Stratton:
>>> so I'm assuming there is some error in there
>>> I thought should raise an exception.
>>
>> Nope, errors don't usually raise exceptions, they just change the return
>> value. Read the manual regarding luaL_dostring(), I don't know how to
>> check its success off the top of my head.
>
>
>
>
> luaL_dostring reurns 1 on error, and in that case you should find a string
> describing the problem at the top of the Lua stack.
>
> Nigel
>
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> configuration take the hassle out of deploying and managing Subversion and
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> download at:  http://p.sf.net/sfu/wandisco-dev2dev
>
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>
>

On Tuesday, August 09, 2011 3:28:14 PM, Josh Stratton wrote:
> Thanks for the responses.  What is the corresponding luabind call
> similar to luaL_dostring that actually throws exceptions?
> 
> On Tue, Aug 9, 2011 at 3:22 PM, Nigel Atkinson<nigel@...>  wrote:
>> On Wed, August 10, 2011 12:43 am, Willi Schinmeyer wrote:
>>
>>> Am Dienstag, den 09.08.2011, 07:17 -0700 schrieb Josh Stratton:
>>>> so I'm assuming there is some error in there
>>>> I thought should raise an exception.
>>>
>>> Nope, errors don't usually raise exceptions, they just change the return
>>> value. Read the manual regarding luaL_dostring(), I don't know how to
>>> check its success off the top of my head.
>>
>>
>>
>>
>> luaL_dostring reurns 1 on error, and in that case you should find a string
>> describing the problem at the top of the Lua stack.
>>
>> Nigel
>>
>> ------------------------------------------------------------------------------
>> uberSVN's rich system and user administration ca
pabilities and model
>> configuration take the hassle out of deploying and managing Subversion and
>> the tools developers use with it. Learn more about uberSVN and get a free
>> download at:  http://p.sf.net/sfu/wandisco-dev2dev
>>
>> _______________________________________________
>> luabind-user mailing list
>> luabind-user@...
>> https://lists.sourceforge.net/lists/listinfo/luabind-user
>>
>>
> 
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There is no single Luabind call tha
t does what luaL_dostring does. You 
have to do all of the individual steps.

You have Lua compile the string into a chunk, using the standard Lua 
API (no exceptions). Then, if it compiled successfully, you have to use 
luabind::from_stack to convert the Lua chunk into a luabind::object 
(note that it will still also be on the stack, so you'll have to deal 
with that). Once it's a luabind::object, you can call it with 
operator().