summaryrefslogtreecommitdiffstats
path: root/include/VBox/com/ErrorInfo.h
blob: 10631a06c928d584a2005244b17830be9d4b3b96 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
/** @file
 * MS COM / XPCOM Abstraction Layer - ErrorInfo class declaration.
 */

/*
 * Copyright (C) 2006-2023 Oracle and/or its affiliates.
 *
 * This file is part of VirtualBox base platform packages, as
 * available from https://www.virtualbox.org.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation, in version 3 of the
 * License.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see <https://www.gnu.org/licenses>.
 *
 * The contents of this file may alternatively be used under the terms
 * of the Common Development and Distribution License Version 1.0
 * (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
 * in the VirtualBox distribution, in which case the provisions of the
 * CDDL are applicable instead of those of the GPL.
 *
 * You may elect to license modified versions of this file under the
 * terms and conditions of either the GPL or the CDDL or both.
 *
 * SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
 */

#ifndef VBOX_INCLUDED_com_ErrorInfo_h
#define VBOX_INCLUDED_com_ErrorInfo_h
#ifndef RT_WITHOUT_PRAGMA_ONCE
# pragma once
#endif

#include "VBox/com/ptr.h"
#include "VBox/com/string.h"
#include "VBox/com/Guid.h"
#include "VBox/com/assert.h"


/** @defgroup grp_com_errinfo   ErrorInfo Classes
 * @ingroup grp_com
 * @{
 */

COM_STRUCT_OR_CLASS(IProgress);
COM_STRUCT_OR_CLASS(IVirtualBoxErrorInfo);

namespace com
{

/**
 * General discussion:
 *
 * In COM all errors are stored on a per thread basis. In general this means
 * only _one_ active error is possible per thread. A new error will overwrite
 * the previous one. To prevent this use MultiResult or ErrorInfoKeeper (see
 * below). The implementations in MSCOM/XPCOM differ slightly, but the details
 * are handled by this glue code.
 *
 * We have different classes which are involved in the error management. I try
 * to describe them separately to make clear what they are there for.
 *
 * ErrorInfo:
 *
 *  This class is able to retrieve the per thread error and store it into its
 *  member variables. This class can also handle non-VirtualBox errors (like
 *  standard COM errors).
 *
 * ProgressErrorInfo:
 *
 *  This is just a simple wrapper class to get the ErrorInfo stored within an
 *  IProgress object. That is the error which was stored when the progress
 *  object was in use and not an error produced by IProgress itself.
 *
 * IVirtualBoxErrorInfo:
 *
 *  The VirtualBox interface class for accessing error information from Main
 *  clients. This class is also used for storing the error information in the
 *  thread context.
 *
 * ErrorInfoKeeper:
 *
 *  A helper class which stores the current per thread info internally. After
 *  calling methods which may produce other errors it is possible to restore
 *  the previous error and therefore restore the situation before calling the
 *  other methods.
 *
 * MultiResult:
 *
 *  Creating an instance of MultiResult turns error chain saving on. All errors
 *  which follow will be saved in a chain for later access.
 *
 * COMErrorInfo (Qt/Gui only):
 *
 *  The Qt GUI does some additional work for saving errors. Because we create
 *  wrappers for _every_ COM call, it is possible to automatically save the
 *  error info after the execution. This allow some additional info like saving
 *  the callee. Please note that this error info is saved on the client side
 *  and therefore locally to the object instance. See COMBaseWithEI,
 *  COMErrorInfo and the generated COMWrappers.cpp in the GUI.
 *
 * Errors itself are set in VirtualBoxBase::setErrorInternal. First a
 * IVirtualBoxErrorInfo object is created and the given error is saved within.
 * If MultiResult is active the current per thread error is fetched and
 * attached to the new created IVirtualBoxErrorInfo object. Next this object is
 * set as the new per thread error.
 *
 * Some general hints:
 *
 * - Always use setError, especially when you are working in an asynchronous thread
 *   to indicate an error. Otherwise the error information itself will not make
 *   it into the client.
 *
 */

/**
 *  The ErrorInfo class provides a convenient way to retrieve error
 *  information set by the most recent interface method, that was invoked on
 *  the current thread and returned an unsuccessful result code.
 *
 *  Once the instance of this class is created, the error information for
 *  the current thread is cleared.
 *
 *  There is no sense to use instances of this class after the last
 *  invoked interface method returns a success.
 *
 *  The class usage pattern is as follows:
 *  <code>
 *      IFoo *foo;
 *      ...
 *      HRESULT rc = foo->SomeMethod();
 *      if (FAILED(rc)) {
 *          ErrorInfo info(foo);
 *          if (info.isFullAvailable()) {
 *              printf("error message = %ls\n", info.getText().raw());
 *          }
 *      }
 *  </code>
 *
 *  This class fetches error information using the IErrorInfo interface on
 *  Win32 (MS COM) or the nsIException interface on other platforms (XPCOM),
 *  or the extended IVirtualBoxErrorInfo interface when when it is available
 *  (i.e. a given IErrorInfo or nsIException instance implements it).
 *  Currently, IVirtualBoxErrorInfo is only available for VirtualBox components.
 *
 *  ErrorInfo::isFullAvailable() and ErrorInfo::isBasicAvailable() determine
 *  what level of error information is available. If #isBasicAvailable()
 *  returns true, it means that only IErrorInfo or nsIException is available as
 *  the source of information (depending on the platform), but not
 *  IVirtualBoxErrorInfo. If #isFullAvailable() returns true, it means that all
 *  three interfaces are available. If both methods return false, no error info
 *  is available at all.
 *
 *  Here is a table of correspondence between this class methods and
 *  and IErrorInfo/nsIException/IVirtualBoxErrorInfo attributes/methods:
 *
 *  ErrorInfo       IErrorInfo      nsIException    IVirtualBoxErrorInfo
 *  --------------------------------------------------------------------
 *  getResultCode   --              result          resultCode
 *  getIID          GetGUID         --              interfaceID
 *  getComponent    GetSource       --              component
 *  getText         GetDescription  message         text
 *
 *  '--' means that this interface does not provide the corresponding portion
 *  of information, therefore it is useless to query it if only
 *  #isBasicAvailable() returns true. As it can be seen, the amount of
 *  information provided at the basic level, depends on the platform
 *  (MS COM or XPCOM).
 */
class ErrorInfo
{
public:

    /**
     *  Constructs a new, "interfaceless" ErrorInfo instance that takes
     *  the error information possibly set on the current thread by an
     *  interface method of some COM component or by the COM subsystem.
     *
     *  This constructor is useful, for example, after an unsuccessful attempt
     *  to instantiate (create) a component, so there is no any valid interface
     *  pointer available.
     */
    explicit ErrorInfo()
        : mIsBasicAvailable(false),
          mIsFullAvailable(false),
          mResultCode(S_OK),
          mResultDetail(0),
          m_pNext(NULL)
    {
        init();
    }

    ErrorInfo(IUnknown *pObj, const GUID &aIID)
        : mIsBasicAvailable(false),
          mIsFullAvailable(false),
          mResultCode(S_OK),
          mResultDetail(0),
          m_pNext(NULL)
    {
        init(pObj, aIID);
    }

    /** Specialization for the IVirtualBoxErrorInfo smart pointer */
    ErrorInfo(const ComPtr<IVirtualBoxErrorInfo> &aPtr)
        : mIsBasicAvailable(false), mIsFullAvailable(false)
        , mResultCode(S_OK), mResultDetail(0)
        { init(aPtr); }

    /**
     *  Constructs a new ErrorInfo instance from the IVirtualBoxErrorInfo
     *  interface pointer. If this pointer is not NULL, both #isFullAvailable()
     *  and #isBasicAvailable() will return |true|.
     *
     *  @param aInfo    pointer to the IVirtualBoxErrorInfo interface that
     *                  holds error info to be fetched by this instance
     */
    ErrorInfo(IVirtualBoxErrorInfo *aInfo)
        : mIsBasicAvailable(false), mIsFullAvailable(false)
        , mResultCode(S_OK), mResultDetail(0)
        { init(aInfo); }

    ErrorInfo(const ErrorInfo &x)
    {
        copyFrom(x);
    }

    virtual ~ErrorInfo()
    {
        cleanup();
    }

    ErrorInfo& operator=(const ErrorInfo& x)
    {
        cleanup();
        copyFrom(x);
        return *this;
    }

    /**
     *  Returns whether basic error info is actually available for the current
     *  thread. If the instance was created from an interface pointer that
     *  supports basic error info and successfully provided it, or if it is an
     *  "interfaceless" instance and there is some error info for the current
     *  thread, the returned value will be true.
     *
     *  See the class description for details about the basic error info level.
     *
     *  The appropriate methods of this class provide meaningful info only when
     *  this method returns true (otherwise they simply return NULL-like values).
     */
    bool isBasicAvailable() const
    {
        return mIsBasicAvailable;
    }

    /**
     *  Returns whether full error info is actually available for the current
     *  thread. If the instance was created from an interface pointer that
     *  supports full error info and successfully provided it, or if it is an
     *  "interfaceless" instance and there is some error info for the current
     *  thread, the returned value will be true.
     *
     *  See the class description for details about the full error info level.
     *
     *  The appropriate methods of this class provide meaningful info only when
     *  this method returns true (otherwise they simply return NULL-like values).
     */
    bool isFullAvailable() const
    {
        return mIsFullAvailable;
    }

    /**
     *  Returns the COM result code of the failed operation.
     */
    HRESULT getResultCode() const
    {
        return mResultCode;
    }

    /**
     *  Returns the (optional) result detail code of the failed operation.
     */
    LONG getResultDetail() const
    {
        return mResultDetail;
    }

    /**
     *  Returns the IID of the interface that defined the error.
     */
    const Guid& getInterfaceID() const
    {
        return mInterfaceID;
    }

    /**
     *  Returns the name of the component that generated the error.
     */
    const Bstr& getComponent() const
    {
        return mComponent;
    }

    /**
     *  Returns the textual description of the error.
     */
    const Bstr& getText() const
    {
        return mText;
    }

    /**
     *  Returns the next error information object or @c NULL if there is none.
     */
    const ErrorInfo* getNext() const
    {
        return m_pNext;
    }

    /**
     *  Returns the name of the interface that defined the error
     */
    const Bstr& getInterfaceName() const
    {
        return mInterfaceName;
    }

    /**
     *  Returns the IID of the interface that returned the error.
     *
     *  This method returns a non-null IID only if the instance was created
     *  using template \<class I\> ErrorInfo(I *i) or
     *  template \<class I\> ErrorInfo(const ComPtr<I> &i) constructor.
     *
     *  @todo broken ErrorInfo documentation links, possibly misleading.
     */
    const Guid& getCalleeIID() const
    {
        return mCalleeIID;
    }

    /**
     *  Returns the name of the interface that returned the error
     *
     *  This method returns a non-null name only if the instance was created
     *  using template \<class I\> ErrorInfo(I *i) or
     *  template \<class I\> ErrorInfo(const ComPtr<I> &i) constructor.
     *
     *  @todo broken ErrorInfo documentation links, possibly misleading.
     */
    const Bstr& getCalleeName() const
    {
        return mCalleeName;
    }

    HRESULT getVirtualBoxErrorInfo(ComPtr<IVirtualBoxErrorInfo> &pVirtualBoxErrorInfo);

    /**
     *  Resets all collected error information. #isBasicAvailable() and
     *  #isFullAvailable will return @c true after this method is called.
     */
    void setNull()
    {
        cleanup();
    }

protected:

    ErrorInfo(bool /* aDummy */)
        : mIsBasicAvailable(false),
          mIsFullAvailable(false),
          mResultCode(S_OK),
          m_pNext(NULL)
    { }

    void copyFrom(const ErrorInfo &x);
    void cleanup();

    void init(bool aKeepObj = false);
    void init(IUnknown *aUnk, const GUID &aIID, bool aKeepObj = false);
    void init(IVirtualBoxErrorInfo *aInfo);

    bool mIsBasicAvailable : 1;
    bool mIsFullAvailable : 1;

    HRESULT mResultCode;
    LONG    mResultDetail;
    Guid    mInterfaceID;
    Bstr    mComponent;
    Bstr    mText;

    ErrorInfo *m_pNext;

    Bstr mInterfaceName;
    Guid mCalleeIID;
    Bstr mCalleeName;

    ComPtr<IUnknown> mErrorInfo;
};

/**
 *  A convenience subclass of ErrorInfo that, given an IProgress interface
 *  pointer, reads its errorInfo attribute and uses the returned
 *  IVirtualBoxErrorInfo instance to construct itself.
 */
class ProgressErrorInfo : public ErrorInfo
{
public:

    /**
     *  Constructs a new instance by fetching error information from the
     *  IProgress interface pointer. If the progress object is not NULL,
     *  its completed attribute is true, resultCode represents a failure,
     *  and the errorInfo attribute returns a valid IVirtualBoxErrorInfo pointer,
     *  both #isFullAvailable() and #isBasicAvailable() will return true.
     *
     *  @param  progress    the progress object representing a failed operation
     */
    ProgressErrorInfo(IProgress *progress);
};

/**
 *  A convenience subclass of ErrorInfo that allows to preserve the current
 *  error info. Instances of this class fetch an error info object set on the
 *  current thread and keep a reference to it, which allows to restore it
 *  later using the #restore() method. This is useful to preserve error
 *  information returned by some method for the duration of making another COM
 *  call that may set its own error info and overwrite the existing
 *  one. Preserving and restoring error information makes sense when some
 *  method wants to return error information set by other call as its own
 *  error information while it still needs to make another call before return.
 *
 *  Instead of calling #restore() explicitly you may let the object destructor
 *  do it for you, if you correctly limit the object's lifetime.
 *
 *  The usage pattern is:
 *  <code>
 *      rc = foo->method();
 *      if (FAILED(rc))
 *      {
 *           ErrorInfoKeeper eik;
 *           ...
 *           // bar may return error info as well
 *           bar->method();
 *           ...
 *           // no need to call #restore() explicitly here because the eik's
 *           // destructor will restore error info fetched after the failed
 *           // call to foo before returning to the caller
 *           return rc;
 *      }
 *  </code>
 */
class ErrorInfoKeeper : public ErrorInfo
{
public:

    /**
     *  Constructs a new instance that will fetch the current error info if
     *  @a aIsNull is @c false (by default) or remain uninitialized (null)
     *  otherwise.
     *
     *  @param aIsNull  @c true to prevent fetching error info and leave
     *                  the instance uninitialized.
     */
    ErrorInfoKeeper(bool aIsNull = false)
        : ErrorInfo(false), mForgot(aIsNull)
    {
        if (!aIsNull)
            init(true /* aKeepObj */);
    }

    /**
     *  Constructs a new instance from an ErrorInfo object, to inject a full
     *  error info created elsewhere.
     *
     *  @param aInfo    @c true to prevent fetching error info and leave
     *                  the instance uninitialized.
     */
    ErrorInfoKeeper(const ErrorInfo &aInfo)
        : ErrorInfo(false), mForgot(false)
    {
        copyFrom(aInfo);
    }

    /**
     *  Destroys this instance and automatically calls #restore() which will
     *  either restore error info fetched by the constructor or do nothing
     *  if #forget() was called before destruction.
     */
    ~ErrorInfoKeeper() { if (!mForgot) restore(); }

    /**
     *  Tries to (re-)fetch error info set on the current thread.  On success,
     *  the previous error information, if any, will be overwritten with the
     *  new error information. On failure, or if there is no error information
     *  available, this instance will be reset to null.
     */
    void fetch()
    {
        setNull();
        mForgot = false;
        init(true /* aKeepObj */);
    }

    /**
     *  Restores error info fetched by the constructor and forgets it
     *  afterwards. Does nothing if the error info was forgotten by #forget().
     *
     *  @return COM result of the restore operation.
     */
    HRESULT restore();

    /**
     *  Forgets error info fetched by the constructor to prevent it from
     *  being restored by #restore() or by the destructor.
     */
    void forget() { mForgot = true; }

    /**
     *  Forgets error info fetched by the constructor to prevent it from
     *  being restored by #restore() or by the destructor, and returns the
     *  stored error info object to the caller.
     */
    ComPtr<IUnknown> takeError() { mForgot = true; return mErrorInfo; }

private:

    bool mForgot : 1;
};

} /* namespace com */

/** @} */

#endif /* !VBOX_INCLUDED_com_ErrorInfo_h */