digitalmars.D.learn - Segmentation fault while creating a class object by dlsym-ed function
- Konstantin J. Chernov (54/54) Jul 17 2012 Hello. When I'm trying to create a class object by using a
- Jacob Carlborg (5/14) Jul 17 2012 Dynamic libraries aren't properly supported by the runtime.
- Konstantin J. Chernov (4/8) Jul 18 2012 That's terrible:(
- Jacob Carlborg (5/13) Jul 18 2012 No, not that I can think of for now. But it's a known problem that is
- bearophile (4/11) Jul 18 2012 And usually you don't need to write .di files in D.
- =?UTF-8?B?QWxleCBSw7hubmUgUGV0ZXJzZW4=?= (38/89) Jul 18 2012 As Jacob said, the D runtime isn't quite ready for shared libraries yet.
- Konstantin J. Chernov (53/53) Jul 18 2012 Thank you for your replies!
- Alexandr Druzhinin (5/5) Jul 18 2012 Probably you mean the same problem that is described in the thread
Hello. When I'm trying to create a class object by using a
dlsym-ed function, I'm getting a segmentation fault after
execution of program.
However, if I'm deleting that object before 'return 0' in main
(by using 'delete b'), everything is going fine.
I'm just started to learn D after using C++ for more than 5
years, so some things look really strange for me (especially that
'new className()' doesn't return a pointer).
What am I doing wrong here? Is there any way to do what I'm
trying to do right way?
Thanks.
test.d:
import std.c.linux.linux;
import std.stdio;
import testclass;
int main(string[] args)
{
void* handle = dlopen("./testclass.so", RTLD_LAZY |
RTLD_LOCAL);
testclass function(wstring) a;
a = cast(testclass function(wstring))dlsym(handle,
"loadClass");
testclass b = a("test");
return 0;
}
testclass.di:
class testclass
{
this(const wstring loadmsg);
~this();
wstring foo();
};
testclass.d:
import std.stdio;
class testclass
{
private wstring msg;
this(const wstring loadmsg)
{
writeln("Class constructor");
this.msg = loadmsg;
}
~this()
{
}
wstring foo()
{
return msg;
}
};
extern(C) testclass loadClass(const wstring loadmsg)
{
return new testclass(loadmsg);
}
Jul 17 2012
On 2012-07-18 06:51, Konstantin J. Chernov wrote:Hello. When I'm trying to create a class object by using a dlsym-ed function, I'm getting a segmentation fault after execution of program. However, if I'm deleting that object before 'return 0' in main (by using 'delete b'), everything is going fine. I'm just started to learn D after using C++ for more than 5 years, so some things look really strange for me (especially that 'new className()' doesn't return a pointer).Classes are always references.What am I doing wrong here? Is there any way to do what I'm trying to do right way?Dynamic libraries aren't properly supported by the runtime. -- /Jacob Carlborg
Jul 17 2012
That's terrible:( It's so nice to make an interface, and create classes that inherit this interface dynamically, without linking... Maybe there's another way?What am I doing wrong here? Is there any way to do what I'm trying to do right way?Dynamic libraries aren't properly supported by the runtime.
Jul 18 2012
Jacob Carlborg <doob me.com> On 2012-07-18 10:17, Konstantin J. Chernov wrote:No, not that I can think of for now. But it's a known problem that is being worked on: https://github.com/dawgfoto/druntime/tree/SharedRuntime -- /Jacob CarlborgThat's terrible:( It's so nice to make an interface, and create classes that inherit this interface dynamically, without linking... Maybe there's another way?What am I doing wrong here? Is there any way to do what I'm trying to do right way?Dynamic libraries aren't properly supported by the runtime.
Jul 18 2012
Konstantin J. Chernov:
testclass.di:
class testclass
{
this(const wstring loadmsg);
~this();
wstring foo();
};
And usually you don't need to write .di files in D.
Bye,
bearophile
Jul 18 2012
On 18-07-2012 06:51, Konstantin J. Chernov wrote:
Hello. When I'm trying to create a class object by using a dlsym-ed
function, I'm getting a segmentation fault after execution of program.
However, if I'm deleting that object before 'return 0' in main (by using
'delete b'), everything is going fine.
I'm just started to learn D after using C++ for more than 5 years, so
some things look really strange for me (especially that 'new
className()' doesn't return a pointer).
What am I doing wrong here? Is there any way to do what I'm trying to do
right way?
Thanks.
test.d:
import std.c.linux.linux;
import std.stdio;
import testclass;
int main(string[] args)
{
void* handle = dlopen("./testclass.so", RTLD_LAZY | RTLD_LOCAL);
testclass function(wstring) a;
a = cast(testclass function(wstring))dlsym(handle, "loadClass");
testclass b = a("test");
return 0;
}
testclass.di:
class testclass
{
this(const wstring loadmsg);
~this();
wstring foo();
};
testclass.d:
import std.stdio;
class testclass
{
private wstring msg;
this(const wstring loadmsg)
{
writeln("Class constructor");
this.msg = loadmsg;
}
~this()
{
}
wstring foo()
{
return msg;
}
};
extern(C) testclass loadClass(const wstring loadmsg)
{
return new testclass(loadmsg);
}
As Jacob said, the D runtime isn't quite ready for shared libraries yet.
What you can do, however, is provide a bit of inversion of control to
make the allocation happen from the runtime linked statically to your
application:
import std.conv;
alias extern (C) void* function(size_t) Allocator;
extern (C) testclass loadClass(Allocator allocator, const wstring loadmsg)
{
auto size = __traits(classInstanceSize, testclass);
auto mem = allocator(size);
return emplace!testclass(mem[0 .. size], loadmsg);
}
Then in the application:
import core.memory;
import core.sys.posix.dlfcn;
import std.stdio;
import testclass;
void* allocate(size_t size)
{
return GC.malloc(size);
}
int main(string[] args)
{
auto h = dlopen("./testclass.so", RTLD_LAZY | RTLD_LOCAL);
auto a = cast(testclass function(Allocator, wstring))dlsym(h,
"loadClass");
auto b = a(&allocate, "test");
return 0;
}
This should make allocation work, but I haven't actually tested it. Note
also that even if it does work, things get more complicated when the
class you're allocating has a finalizer, for example (see
http://dlang.org/phobos/core_memory.html#FINALIZE).
--
Alex Rønne Petersen
alex lycus.org
http://lycus.org
Jul 18 2012
Thank you for your replies!
I've found a working solution - all I needed is to change wstring
to const wstring, and pass it not as func("something"), but as
wstring tmp = "something"; func(tmp);
That's really odd, because I don't understand, how those changes
made segfault disappear.
Here's the working code:
test.d:
import std.c.linux.linux;
import std.stdio;
import testclass;
int main(string[] args)
{
void* handle = dlopen("./testclass.so", RTLD_LAZY |
RTLD_LOCAL);
testclass function(const wstring) a;
a = cast(testclass function(const wstring))dlsym(handle,
"loadClass");
wstring tmp = "Test";
testclass b = a(tmp);
return 0;
}
testclass.di:
class testclass
{
this(const wstring loadmsg);
~this();
wstring foo();
};
testclass.d:
import std.stdio;
class testclass
{
private wstring msg;
this(const wstring loadmsg)
{
writeln("Class constructor");
this.msg = loadmsg;
}
~this()
{
}
wstring foo()
{
return msg;
}
};
extern(C) testclass loadClass(const wstring loadmsg)
{
return new testclass(loadmsg);
}
dmd test.d -L-ldl
dmd testclass.d -fPIC -shared
Jul 18 2012
Probably you mean the same problem that is described in the thread avobe, see "using GC needs particular skills?" Every time after execution my code I got very frustating access violation and the problem was misunderstanding garbage collector because I've never used it before.
Jul 18 2012