| Topic: |
DEVELOP > c-Plus-Plus |
| User: |
"wrungel" |
| Date: |
18 Dec 2007 11:36:14 AM |
| Object: |
un-catched Exceptions in mixed C/C++ code |
Exceptions thrown by C++ function which is called by a C-function
which is called by a C++ function are not catched by outermost C++
function.
Operating system: Linux
Compiler: GNU GCC Version 4.2.1
file x.cc:
main ()
{
try {
y_func();
} catch (...) {
cout << "This line is NOT executed if _func() is compiled with C+
+ compiler";
}
}
file y.c:
y_func()
{
z_func();
}
file z.cc:
z_func()
{
throw exception;
}
Files x.cc and z.cc are compiled with C++ (GNU) compiler.
File y.c is compiled with C (GNU) compiler.
If z_func() throws, exception is not catched by main function.
Program crashes with error message: terminate called after throwing of
an instance 'of std::exception'
If y.c is compiled with C++ (GNU) compiler, exception is catched by
main function (desired behavior).
The complete source code can be downloaded here:
http://freenet-homepage.de/wrungel/exceptions.tgz
The problem is that the y_func() comes from third-party library and
can not be recompiled with C compiler.
How can I catch exceptions in main function caused by z_func()?
.
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| User: "Kira Yamato" |
|
| Title: Re: un-catched Exceptions in mixed C/C++ code |
18 Dec 2007 12:05:23 PM |
|
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On 2007-12-18 12:36:14 -0500, wrungel <wrungel@web.de> said:
Exceptions thrown by C++ function which is called by a C-function
which is called by a C++ function are not catched by outermost C++
function.
Operating system: Linux
Compiler: GNU GCC Version 4.2.1
file x.cc:
main ()
{
try {
y_func();
} catch (...) {
cout << "This line is NOT executed if _func() is compiled with C+
+ compiler";
}
}
file y.c:
y_func()
{
z_func();
}
file z.cc:
z_func()
{
throw exception;
}
Files x.cc and z.cc are compiled with C++ (GNU) compiler.
File y.c is compiled with C (GNU) compiler.
If z_func() throws, exception is not catched by main function.
Program crashes with error message: terminate called after throwing of
an instance 'of std::exception'
If y.c is compiled with C++ (GNU) compiler, exception is catched by
main function (desired behavior).
The complete source code can be downloaded here:
http://freenet-homepage.de/wrungel/exceptions.tgz
The problem is that the y_func() comes from third-party library and
can not be recompiled with C compiler.
How can I catch exceptions in main function caused by z_func()?
How did you get the linker to be able to let the C translation unit
(y.c) see the C++ function in the C++ translation unit (z.cc)?
Sorry that I couldn't refer to your source code. My Mac cannot
recognize the gtar format.
--
-kira
.
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| User: "wrungel" |
|
| Title: Re: un-catched Exceptions in mixed C/C++ code |
18 Dec 2007 12:10:43 PM |
|
|
On 18 Dez., 19:05, Kira Yamato <kira...@earthlink.net> wrote:
How did you get the linker to be able to let the C translation unit
(y.c) see the C++ function in the C++ translation unit (z.cc)?
Sorry that I couldn't refer to your source code. My Mac cannot
recognize the gtar format.
Using extern "C" declarations for y_func() and z_func().
I uploaded same code as zip archive:
http://freenet-homepage.de/wrungel/exceptions.zip
.
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| User: "Kira Yamato" |
|
| Title: Re: un-catched Exceptions in mixed C/C++ code |
18 Dec 2007 12:22:29 PM |
|
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On 2007-12-18 13:10:43 -0500, wrungel <wrungel@web.de> said:
On 18 Dez., 19:05, Kira Yamato <kira...@earthlink.net> wrote:
How did you get the linker to be able to let the C translation unit
(y.c) see the C++ function in the C++ translation unit (z.cc)?
Sorry that I couldn't refer to your source code. My Mac cannot
recognize the gtar format.
Using extern "C" declarations for y_func() and z_func().
I uploaded same code as zip archive:
http://freenet-homepage.de/wrungel/exceptions.zip
I think this is the problem: you've declared z_func() with extern "C".
The following test program
#include <iostream>
using namespace std;
extern "C"
{
void callc()
{
throw "oh no!";
}
};
int main()
{
callc();
return 0;
}
causes the runtime error message:
terminate called after throwing an instance of 'char const*'
Abort trap
So, I suppose declaring a function extern "C" changes the way it uses
the stack; hence giving you problems when that function throws an
exception.
It seems that there is no way to throw an exception across a stack
frame involving a genuine C function.
--
-kira
.
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|
| User: "Pete Becker" |
|
| Title: Re: un-catched Exceptions in mixed C/C++ code |
18 Dec 2007 12:54:18 PM |
|
|
On 2007-12-18 13:22:29 -0500, Kira Yamato <kirakun@earthlink.net> said:
On 2007-12-18 13:10:43 -0500, wrungel <wrungel@web.de> said:
On 18 Dez., 19:05, Kira Yamato <kira...@earthlink.net> wrote:
How did you get the linker to be able to let the C translation unit
(y.c) see the C++ function in the C++ translation unit (z.cc)?
Sorry that I couldn't refer to your source code. My Mac cannot
recognize the gtar format.
Using extern "C" declarations for y_func() and z_func().
I uploaded same code as zip archive:
http://freenet-homepage.de/wrungel/exceptions.zip
I think this is the problem: you've declared z_func() with extern "C".
No, that's got nothing to do with it.
The following test program
#include <iostream>
using namespace std;
extern "C"
{
void callc()
{
throw "oh no!";
}
};
int main()
{
callc();
return 0;
}
causes the runtime error message:
terminate called after throwing an instance of 'char const*'
Abort trap
As it should. There's no catch clause. If you wrap the call to callc()
in a try/catch block, this will work just fine.
So, I suppose declaring a function extern "C" changes the way it uses
the stack; hence giving you problems when that function throws an
exception.
No, extern "C" functions can still throw and catch exceptions if
they're compiled as C++.
It seems that there is no way to throw an exception across a stack
frame involving a genuine C function.
That's a different matter. A C function, compiled with a C compiler,
doesn't know anything about exceptions.
--
Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com) Author of "The
Standard C++ Library Extensions: a Tutorial and Reference
(www.petebecker.com/tr1book)
.
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| User: "Kira Yamato" |
|
| Title: Re: un-catched Exceptions in mixed C/C++ code |
18 Dec 2007 01:04:51 PM |
|
|
On 2007-12-18 13:54:18 -0500, Pete Becker <pete@versatilecoding.com> said:
The following test program
#include <iostream>
using namespace std;
extern "C"
{
void callc()
{
throw "oh no!";
}
};
int main()
{
callc();
return 0;
}
causes the runtime error message:
terminate called after throwing an instance of 'char const*'
Abort trap
As it should. There's no catch clause. If you wrap the call to callc()
in a try/catch block, this will work just fine.
Ah, silly me. :) You're right. Sorry about that.
--
-kira
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| User: "=?UTF-8?B?RXJpayBXaWtzdHLDtm0=?=" |
|
| Title: Re: un-catched Exceptions in mixed C/C++ code |
18 Dec 2007 11:56:25 AM |
|
|
On 2007-12-18 18:36, wrungel wrote:
Exceptions thrown by C++ function which is called by a C-function
which is called by a C++ function are not catched by outermost C++
function.
Operating system: Linux
Compiler: GNU GCC Version 4.2.1
file x.cc:
main ()
{
try {
y_func();
} catch (...) {
cout << "This line is NOT executed if _func() is compiled with C+
+ compiler";
}
}
file y.c:
y_func()
{
z_func();
}
file z.cc:
z_func()
{
throw exception;
}
Files x.cc and z.cc are compiled with C++ (GNU) compiler.
File y.c is compiled with C (GNU) compiler.
If z_func() throws, exception is not catched by main function.
Program crashes with error message: terminate called after throwing of
an instance 'of std::exception'
If y.c is compiled with C++ (GNU) compiler, exception is catched by
main function (desired behavior).
The complete source code can be downloaded here:
http://freenet-homepage.de/wrungel/exceptions.tgz
The problem is that the y_func() comes from third-party library and
can not be recompiled with C compiler.
How can I catch exceptions in main function caused by z_func()?
You have to catch the exceptions in z_func() and convert them to error
codes or something like that (setting a global flag?) and then check for
that in main().
--
Erik Wikström
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| User: "Abhishek Padmanabh" |
|
| Title: Re: un-catched Exceptions in mixed C/C++ code |
18 Dec 2007 12:10:34 PM |
|
|
On Dec 18, 10:36 pm, wrungel <wrun...@web.de> wrote:
Exceptions thrown by C++ function which is called by a C-function
which is called by a C++ function are not catched by outermost C++
function.
Operating system: Linux
Compiler: GNU GCC Version 4.2.1
file x.cc:
main ()
{
try {
y_func();
} catch (...) {
cout << "This line is NOT executed if _func() is compiled with C+
+ compiler";
}
}
file y.c:
y_func()
{
z_func();
}
file z.cc:
z_func()
{
throw exception;
}
Files x.cc and z.cc are compiled with C++ (GNU) compiler.
File y.c is compiled with C (GNU) compiler.
If z_func() throws, exception is not catched by main function.
Program crashes with error message: terminate called after throwing of
an instance 'of std::exception'
If y.c is compiled with C++ (GNU) compiler, exception is catched by
main function (desired behavior).
The complete source code can be downloaded here:http://freenet-homepage.de/wrungel/exceptions.tgz
The problem is that the y_func() comes from third-party library and
can not be recompiled with C compiler.
How can I catch exceptions in main function caused by z_func()?
y_func() is not yours, is z_func() your code? Can you change it? C
does not have notion of expcetions. So, an exception thrown from C++
code cannot be caught or translated or left to be caught by the
enclosing caller. You will have to not let any C++ exceptions pass
through z_func(). Uncaught exceptions, in a way, form part of the
interface contract (C++ has exception specifications, as well).
Similar to why you cannot have the C++ function z_func() not use
reference arguments (or reference return types), or any other C++
types, not even std::string/std::vector.
.
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| User: "wrungel" |
|
| Title: Re: un-catched Exceptions in mixed C/C++ code |
18 Dec 2007 12:17:19 PM |
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On 18 Dez., 19:10, Abhishek Padmanabh <abhishek.padman...@gmail.com>
wrote:
y_func() is not yours, is z_func() your code? Can you change it?
z_func() is coded by me.
z_func() is a callback function called by y_func() which is a third-
party libarary function.
Therefore I can not change or recompile y_func().
C does not have notion of expcetions. So, an exception thrown from C++
code cannot be caught or translated or left to be caught by the
enclosing caller.
This is NOT true if you are using GCC.
The option -fexceptions enables exception handling (passing through)
by C-functions.
But I can not use this option for y_func() because I can not recompile
it.
.
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