Re: 回复： Re: Problem calling c++ from Lua (MS-Windows version)

[jseb <gmane2010@...>]

> A very useful tool to debug such DLL problems is Dependency Walker
> [1]. It can tell you what dependencies a DLL has (and it displays
> warning if it's unable to find them). It is also useful to examine
> exported symbols, and check that your luaopen_foo is properly named
> and not mangled.
>
> And to find out why -static-libgcc solves the problem, and how to
> solve it with MSVC, you will have to provide more details, such as
> what DLL exactly is reported missing, what unusual things you might
> have in your PATH, or whether you may have several foo.dll files in
> the PATH (for example one for the C/C++ library, and one for the Lua/C
> binding module).
>
> [1] http://www.dependencywalker.com/


my %PATH% was "classic", nothing strange in it (i checked it with

echo $PATH | awk 'BEGIN { FS=":"} {for (i=1; i<NF; i++) print $i}'

(sorry i don't know how to do it fast with Lua) )

I've got only one "foo.dll". I didn't verify if windows installed one in 
its system-path, but i don't think so.

I checked name mangle, which was ok with "objdump" (or "nm", don't 
remember). Anyway, compiling with static version of gcc standard lib 
solves the issue, so no name mangling here.

And well i do know why i had to add "-static-libgcc".
I wrote the short version, as the story seems to raise few interest. For 
those who are more interested, here's the full story

<found on a forum>
All MinGW executables that uses C/C++ routines, classes and libs are 
necessary linked against libgcc_s_dwxx-x.dll (GNU C lib) and 
libstdc++-xx.dll (GNU C++ STD lib) All these .dll can be found at the 
compiler's /bin directory.
All you have to do is to copy&paste those into your main executable's path.
For a static link version of this libs, you can add "-static-libgcc 
-static-libstdc++" to your compiler flags and you won't need this .dll 
anymore.
Your executable will be dramatically heavier, due to the internal 
addition of their contents, but it should be OK.
</found on a forum>


Now, the mystery is:
Why in shell (CMD or MSYS), during the lua's require, i got this error:

> require "libfoo"
error loading module 'libfoo' from file '.\libfoo.dll':
       Le module spécifié est introuvable.
       (above mean that "specified module could'nt be found)

Ok.
But why when i launch the lua script from explorer (in my case "total 
commander", but that's the same from explorer) i got another error ?
This time, the error was about the missing libgcc_s...dll

I can understand that i don't have problems with MSYS, but the same 
error (that is, missing GNU libc++) should raise with CMD, as it has 
nothing to do with GNU C++ standard lib.

What is missing is something like "strace" under windows, which could 
help to solve this sort of issues (Lua probably hang on this, and report 
a very generic error message).
So i will give a try for dependency-walker, next time i have a 
MS-windows in the neighborhood (no windows here for trying, sorry).

I gave a try with MSVC for trying to figure it out, but i'd rather like 
using GNU's. That's odd that MSVC couldn't compile properly my lib, and 
perhaps it's another problem (i can't believe that Microsoft C++ 
standard library is missing in system32 :p ).


Thanks for the link, i guess it will be useful next time !