Re: Second time's a charm

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On 2/17/06, David Bateman <[email protected]> wrote:
>
> I don't know if I'll be able to help, but will try this weekend..
>
> D.


Send me an email when you start and I'll give you the most updated
information. I have new leads for the cerr stuff:

1) This is apparently related to dynamic linkage. I'm attaching a sample
program to this email that illustrates the problem. I've confirmed that
adding a get_cerr() function to liboctave would solve the problem. (Well, I
don't know what happens if several dll's are involved...)

2) I'm guessing there's some black magic way of doing it directly with the
unmodified dll, but I don't know.

3) The window popping up briefly can be fixed by replacing
-Wl,-subsystem,windows
with
-Wl,-subsystem,console

This will force Windows to open a console for my app and keep it opened. I
think I know how to fix this more elegantly, but that'll have to wait.

Sebastien Loisel

----

$ cat dll.h
#ifdef BUILD_DLL
/* DLL export */
#define EXPORT __declspec(dllexport)
#else
/* EXE import */
#define EXPORT __declspec(dllimport)
#endif
#include <iostream>
EXPORT void hello(void);
//extern EXPORT std::ostream std::cout; don't work
EXPORT std::ostream &get_cout(void);
$ cat dll.cpp
#include <iostream>
#include "dll.h"

EXPORT void hello(void) {
  std::cout<<"Hello";
}
EXPORT std::ostream &get_cout(void) { return std::cout; }
$ cat hello.cpp
#include <iostream>
#include <fstream>
#include "dll.h"

int main () {
  std::streambuf *stdbuf=3Dstd::cout.rdbuf();
  std::ofstream out("foo.txt");
  // std::cout.rdbuf(out.rdbuf()); <-- this doesn't work
  get_cout().rdbuf(out.rdbuf()); // <-- this works
  hello();
  get_cout().rdbuf(stdbuf);
  return 0;
}
$ cat build.sh
#!/bin/sh
g++ -c hello.cpp -o hello.o
g++ -c -DBUILD_DLL dll.cpp -o dll.o
g++ -shared -o message.dll dll.o -Wl,--out-implib,libmessage.a
g++ -o hello.exe hello.o -L./ -lmessage

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On 2/17/06, <b class=3D"gmail_sendername">David Bateman</b> &lt;<a href=3D"=
mailto:[email protected]">[email protected]</a>&gt; wrote=
:<div><span class=3D"gmail_quote"></span><blockquote class=3D"gmail_quote" =
style=3D"border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8=
ex; padding-left: 1ex;">
I don't know if I'll be able to help, but will try this weekend..<br><br>D.=
</blockquote><div><br></div></div>Send me an email when you start and I'll =
give you the most updated information. I have new leads for the cerr stuff:
<br><br>1) This is apparently related to dynamic linkage. I'm attaching a s=
ample program to this email that illustrates the problem. I've confirmed th=
at adding a get_cerr() function to liboctave would solve the problem. (Well=
, I don't know what happens if several dll's are involved...)
<br><br>2) I'm guessing there's some black magic way of doing it directly w=
ith the unmodified dll, but I don't know.<br><br>3) The window popping up b=
riefly can be fixed by replacing<br>-Wl,-subsystem,windows<br>with<br>-Wl,-=
subsystem,console
<br><br>This will force Windows to open a console for my app and keep it op=
ened. I think I know how to fix this more elegantly, but that'll have to wa=
it.<br><br>Sebastien Loisel<br><br>----<br><br>$ cat dll.h<br>#ifdef BUILD_=
DLL
<br>/* DLL export */<br>#define EXPORT __declspec(dllexport)<br>#else<br>/*=
 EXE import */<br>#define EXPORT __declspec(dllimport)<br>#endif<br>#includ=
e &lt;iostream&gt;<br>EXPORT void hello(void);<br>//extern EXPORT std::ostr=
eam std::cout; don't work
<br>EXPORT std::ostream &amp;get_cout(void);<br>$ cat dll.cpp<br>#include &=
lt;iostream&gt;<br>#include &quot;dll.h&quot;<br><br>EXPORT void hello(void=
) {<br>&nbsp; std::cout&lt;&lt;&quot;Hello&quot;;<br>}<br>EXPORT std::ostre=
am &amp;get_cout(void) { return std::cout; }
<br>$ cat hello.cpp<br>#include &lt;iostream&gt;<br>#include &lt;fstream&gt=
;<br>#include &quot;dll.h&quot;<br><br>int main () {<br>&nbsp; std::streamb=
uf *stdbuf=3Dstd::cout.rdbuf();<br>&nbsp; std::ofstream out(&quot;foo.txt&q=
uot;);<br>
&nbsp; // std::cout.rdbuf(out.rdbuf()); &lt;-- this doesn't work<br>&nbsp; =
get_cout().rdbuf(out.rdbuf()); // &lt;-- this works<br>&nbsp; hello();<br>&=
nbsp; get_cout().rdbuf(stdbuf);<br>&nbsp; return 0;<br>}<br>$ cat build.sh<=
br>#!/bin/sh<br>g++ -c=20
hello.cpp -o hello.o<br>g++ -c -DBUILD_DLL dll.cpp -o dll.o<br>g++ -shared =
-o message.dll dll.o -Wl,--out-implib,libmessage.a<br>g++ -o hello.exe hell=
o.o -L./ -lmessage<br><br>

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