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Posted to c-dev@xerces.apache.org by "Robert Buck (JIRA)" <xe...@xml.apache.org> on 2005/01/07 13:51:14 UTC
[jira] Created: (XERCESC-1323) CLONE -XMemory related warning
CLONE -XMemory related warning
------------------------------
Key: XERCESC-1323
URL: http://issues.apache.org/jira/browse/XERCESC-1323
Project: Xerces-C++
Type: Bug
Components: Build
Versions: Nightly build (please specify the date)
Environment: Operating System: Windows NT/2K
Platform: PC
Reporter: Robert Buck
When building (VS.NET 2003) my app with latest CVS snapshot (20031120171656) I
keep getting warning (level 4) :
D:\Utils\xerces\src\xercesc\internal\XSerializeEngine.hpp(664) : warning C4673:
throwing 'xercesc_2_4::XSerializationException' the following types will not be
considered at the catch site
D:\Utils\xerces\src\xercesc\internal\XSerializeEngine.hpp(664) : warning
C4671: 'XMemory' : the copy constructor is inaccessible
I'm not sure if it is really safe to ignore this warning ...
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[jira] Commented: (XERCESC-1323) CLONE -XMemory related warning
Posted by "Robert Buck (JIRA)" <xe...@xml.apache.org>.
[ http://issues.apache.org/jira/browse/XERCESC-1323?page=comments#action_57387 ]
Robert Buck commented on XERCESC-1323:
--------------------------------------
Oh yeah, my email address at MathWorks is Robert.Buck@mathworks.com.
> CLONE -XMemory related warning
> ------------------------------
>
> Key: XERCESC-1323
> URL: http://issues.apache.org/jira/browse/XERCESC-1323
> Project: Xerces-C++
> Type: Bug
> Components: Build
> Versions: Nightly build (please specify the date)
> Environment: Operating System: Windows NT/2K
> Platform: PC
> Reporter: Robert Buck
>
> When building (VS.NET 2003) my app with latest CVS snapshot (20031120171656) I
> keep getting warning (level 4) :
> D:\Utils\xerces\src\xercesc\internal\XSerializeEngine.hpp(664) : warning C4673:
> throwing 'xercesc_2_4::XSerializationException' the following types will not be
> considered at the catch site
> D:\Utils\xerces\src\xercesc\internal\XSerializeEngine.hpp(664) : warning
> C4671: 'XMemory' : the copy constructor is inaccessible
> I'm not sure if it is really safe to ignore this warning ...
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[jira] Resolved: (XERCESC-1323) CLONE -XMemory related warning
Posted by "Alberto Massari (JIRA)" <xe...@xml.apache.org>.
[ http://issues.apache.org/jira/browse/XERCESC-1323?page=history ]
Alberto Massari resolved XERCESC-1323:
--------------------------------------
Resolution: Fixed
Robert, I have committed the changes to XMemory that I explained in the mail to xerces-c-dev. It removes the warning about throwing objects having a base class with a protected copy constructor, without creating an entire new base class for throwable objects.
Please verify and let me know if it's ok for you.
Alberto
> CLONE -XMemory related warning
> ------------------------------
>
> Key: XERCESC-1323
> URL: http://issues.apache.org/jira/browse/XERCESC-1323
> Project: Xerces-C++
> Type: Bug
> Components: Build
> Versions: Nightly build (please specify the date)
> Environment: Operating System: Windows NT/2K
> Platform: PC
> Reporter: Robert Buck
>
> When building (VS.NET 2003) my app with latest CVS snapshot (20031120171656) I
> keep getting warning (level 4) :
> D:\Utils\xerces\src\xercesc\internal\XSerializeEngine.hpp(664) : warning C4673:
> throwing 'xercesc_2_4::XSerializationException' the following types will not be
> considered at the catch site
> D:\Utils\xerces\src\xercesc\internal\XSerializeEngine.hpp(664) : warning
> C4671: 'XMemory' : the copy constructor is inaccessible
> I'm not sure if it is really safe to ignore this warning ...
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[jira] Commented: (XERCESC-1323) CLONE -XMemory related warning
Posted by "Alberto Massari (JIRA)" <xe...@xml.apache.org>.
[ http://issues.apache.org/jira/browse/XERCESC-1323?page=comments#action_57383 ]
Alberto Massari commented on XERCESC-1323:
------------------------------------------
Hi Bob,
I trust you when you say that the C++ specs allow implementation-specific behaviors when not all the inherited copy constructors are public.
But the fix would be to either remove the protected copy constructor of XMemory or make it public, and this is something that goes against the purpose that the writer of that code, Peiyong, had in mind (i.e. preventing XMemory from being used outside a derived class); on the other hand, the warning is reported only by Visual C++, that seems to behave properly when "catch(Type&)" is used.
So, in my opinion, this warning can stay, unless Peiyong agrees that XMemory having a protected constructor (instead of a protected constructor and copy constructor) is enough.
Alberto
> CLONE -XMemory related warning
> ------------------------------
>
> Key: XERCESC-1323
> URL: http://issues.apache.org/jira/browse/XERCESC-1323
> Project: Xerces-C++
> Type: Bug
> Components: Build
> Versions: Nightly build (please specify the date)
> Environment: Operating System: Windows NT/2K
> Platform: PC
> Reporter: Robert Buck
>
> When building (VS.NET 2003) my app with latest CVS snapshot (20031120171656) I
> keep getting warning (level 4) :
> D:\Utils\xerces\src\xercesc\internal\XSerializeEngine.hpp(664) : warning C4673:
> throwing 'xercesc_2_4::XSerializationException' the following types will not be
> considered at the catch site
> D:\Utils\xerces\src\xercesc\internal\XSerializeEngine.hpp(664) : warning
> C4671: 'XMemory' : the copy constructor is inaccessible
> I'm not sure if it is really safe to ignore this warning ...
--
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[jira] Commented: (XERCESC-1323) CLONE -XMemory related warning
Posted by "Robert Buck (JIRA)" <xe...@xml.apache.org>.
[ http://issues.apache.org/jira/browse/XERCESC-1323?page=comments#action_57379 ]
Robert Buck commented on XERCESC-1323:
--------------------------------------
Correction to a typo:
"...whose class or superclasses lack a public copy-constructor..."
> CLONE -XMemory related warning
> ------------------------------
>
> Key: XERCESC-1323
> URL: http://issues.apache.org/jira/browse/XERCESC-1323
> Project: Xerces-C++
> Type: Bug
> Components: Build
> Versions: Nightly build (please specify the date)
> Environment: Operating System: Windows NT/2K
> Platform: PC
> Reporter: Robert Buck
>
> When building (VS.NET 2003) my app with latest CVS snapshot (20031120171656) I
> keep getting warning (level 4) :
> D:\Utils\xerces\src\xercesc\internal\XSerializeEngine.hpp(664) : warning C4673:
> throwing 'xercesc_2_4::XSerializationException' the following types will not be
> considered at the catch site
> D:\Utils\xerces\src\xercesc\internal\XSerializeEngine.hpp(664) : warning
> C4671: 'XMemory' : the copy constructor is inaccessible
> I'm not sure if it is really safe to ignore this warning ...
--
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[jira] Commented: (XERCESC-1323) CLONE -XMemory related warning
Posted by "Robert Buck (JIRA)" <xe...@xml.apache.org>.
[ http://issues.apache.org/jira/browse/XERCESC-1323?page=comments#action_57377 ]
Robert Buck commented on XERCESC-1323:
--------------------------------------
Bottom Line on Top:
Thrown objects MUST have both the destructors and copy constructor exposed; this includes superclasses as well.
Regarding the last comments in the following issue:
http://issues.apache.org/jira/browse/XERCESC-1058
Alby, you are incorrect. This is implementation defined by specification. In many C++ runtime implementations, the object, whose class or superclasses lack a public constructor, cannot be caught by a catch-ref block either. Taking a look at the C++ Std, § 15.1, subsections 4-6, and § 15.4, subsection 18, it is very apparent that Xerces-C is ill-formed.
Please reopen the cited issue, and fix Xerces.
> CLONE -XMemory related warning
> ------------------------------
>
> Key: XERCESC-1323
> URL: http://issues.apache.org/jira/browse/XERCESC-1323
> Project: Xerces-C++
> Type: Bug
> Components: Build
> Versions: Nightly build (please specify the date)
> Environment: Operating System: Windows NT/2K
> Platform: PC
> Reporter: Robert Buck
>
> When building (VS.NET 2003) my app with latest CVS snapshot (20031120171656) I
> keep getting warning (level 4) :
> D:\Utils\xerces\src\xercesc\internal\XSerializeEngine.hpp(664) : warning C4673:
> throwing 'xercesc_2_4::XSerializationException' the following types will not be
> considered at the catch site
> D:\Utils\xerces\src\xercesc\internal\XSerializeEngine.hpp(664) : warning
> C4671: 'XMemory' : the copy constructor is inaccessible
> I'm not sure if it is really safe to ignore this warning ...
--
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[jira] Commented: (XERCESC-1323) CLONE -XMemory related warning
Posted by "Robert Buck (JIRA)" <xe...@xml.apache.org>.
[ http://issues.apache.org/jira/browse/XERCESC-1323?page=comments#action_57386 ]
Robert Buck commented on XERCESC-1323:
--------------------------------------
Hi Alby,
With regards to your last comment, the problem is that the result will be object slicing. Users will not be able to catch the specific exception type.
Compilers are tending to become more stringent with regards to this specific behavior. Microsoft's support for this has come and gone over the years, but now MS is following the spec more closely. Other compilers, especially those that have EDG based front ends (Intel), will have similar issues. The issue will only increase as each compiler becomes more ISO C++ compliant.
I have authored the diagnostics and exception handling framework in MATLAB, and in order to guarantee consistent, correct behavior on the following compilers:
HP aCC
Sun CC
g++
cl.exe
ecc (7.1 is EDG based)
we had to observe the following ground rules:
a. public default constructor
b. public copy constructor
c. public destructor
d. the above for all super classes
e. throw-type, never throw-new
f. catch by reference, never by pointer, nor by value
Given these ground rules, it would make little sense to me for Xerces-C exception classes to derive from XMemory. There is only one case I can think of where you'd want to heap allocate an exception object... For illustration let me refer back to what I wrote for the C++ exception classes in MATLAB. In order to support causation semantics (similar, but superior to what Java has), I did need to heap allocate the chained exception. However in this case, simply using a macro, that defines all the required operator-new and operator-delete static methods for a class was sufficient. The [new and delete] operators would, of course, call the implementation defined memory management functions. The exception classes have a link time dependency upon the exported memory management symbols, and a compile time dependency upon those abstractions, but the memory management abstractions only internally have a compile time dependency; the exported header declares no such dependency.
So a side benefit of this strategy is that the compile time dependency between memory management and exception handling can be broken, benefits which are academic.
My general suggestions are as follows:
1. Create a common base class for all exceptions, perhaps called XercesThrowable
2. Do not have XercesThrowable, nor any other exception type, inherit from XMemory.
3. Follow similar guidelines, as shown above in [a-f].
4. Define a macro (you probably already have one) that defines all twelve (12) static inline new and delete operators, according to ISO C++ § 18.4.1, § 3.7.3, as well as the replacement functions in § 17.4.3.4. For platforms that do not support std::nothrow, you can reduce this to eight (8) methods.
5. Use the macro defined in [4] in each exception class.
If you want a copy of the C++ standard, email me directly your email address at Progress, or a private email, and I will send it to you privately.
> CLONE -XMemory related warning
> ------------------------------
>
> Key: XERCESC-1323
> URL: http://issues.apache.org/jira/browse/XERCESC-1323
> Project: Xerces-C++
> Type: Bug
> Components: Build
> Versions: Nightly build (please specify the date)
> Environment: Operating System: Windows NT/2K
> Platform: PC
> Reporter: Robert Buck
>
> When building (VS.NET 2003) my app with latest CVS snapshot (20031120171656) I
> keep getting warning (level 4) :
> D:\Utils\xerces\src\xercesc\internal\XSerializeEngine.hpp(664) : warning C4673:
> throwing 'xercesc_2_4::XSerializationException' the following types will not be
> considered at the catch site
> D:\Utils\xerces\src\xercesc\internal\XSerializeEngine.hpp(664) : warning
> C4671: 'XMemory' : the copy constructor is inaccessible
> I'm not sure if it is really safe to ignore this warning ...
--
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