Source code

Revision control

Line Code
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
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/* Implementations of runtime and static assertion macros for C and C++. */

#ifndef mozilla_Assertions_h
#define mozilla_Assertions_h

#if defined(MOZILLA_INTERNAL_API) && defined(__cplusplus)
#define MOZ_DUMP_ASSERTION_STACK
#endif

#include "mozilla/Attributes.h"
#include "mozilla/Compiler.h"
#include "mozilla/Likely.h"
#include "mozilla/MacroArgs.h"
#include "mozilla/StaticAnalysisFunctions.h"
#include "mozilla/Types.h"
#ifdef MOZ_DUMP_ASSERTION_STACK
#include "nsTraceRefcnt.h"
#endif

/*
 * The crash reason set by MOZ_CRASH_ANNOTATE is consumed by the crash reporter
 * if present. It is declared here (and defined in Assertions.cpp) to make it
 * available to all code, even libraries that don't link with the crash reporter
 * directly.
 */
MOZ_BEGIN_EXTERN_C
extern MFBT_DATA const char* gMozCrashReason;
MOZ_END_EXTERN_C

#if !defined(DEBUG) && (defined(MOZ_HAS_MOZGLUE) || defined(MOZILLA_INTERNAL_API))
static inline void
AnnotateMozCrashReason(const char* reason)
{
  gMozCrashReason = reason;
}
#  define MOZ_CRASH_ANNOTATE(...) AnnotateMozCrashReason(__VA_ARGS__)
#else
#  define MOZ_CRASH_ANNOTATE(...) do { /* nothing */ } while (0)
#endif

#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#ifdef _MSC_VER
   /*
    * TerminateProcess and GetCurrentProcess are defined in <winbase.h>, which
    * further depends on <windef.h>.  We hardcode these few definitions manually
    * because those headers clutter the global namespace with a significant
    * number of undesired macros and symbols.
    */
MOZ_BEGIN_EXTERN_C
__declspec(dllimport) int __stdcall
TerminateProcess(void* hProcess, unsigned int uExitCode);
__declspec(dllimport) void* __stdcall GetCurrentProcess(void);
MOZ_END_EXTERN_C
#else
#  include <signal.h>
#endif
#ifdef ANDROID
#  include <android/log.h>
#endif

#if defined(__GNUC__)
#  define MOZ_UNUSED_ATTRIBUTE __attribute__((unused))
#else
#  define MOZ_UNUSED_ATTRIBUTE /* nothing */
#endif

/*
 * MOZ_STATIC_ASSERT may be used to assert a condition *at compile time* in C.
 * In C++11, static_assert is provided by the compiler to the same effect.
 * This can be useful when you make certain assumptions about what must hold for
 * optimal, or even correct, behavior.  For example, you might assert that the
 * size of a struct is a multiple of the target architecture's word size:
 *
 *   struct S { ... };
 *   // C
 *   MOZ_STATIC_ASSERT(sizeof(S) % sizeof(size_t) == 0,
 *                     "S should be a multiple of word size for efficiency");
 *   // C++11
 *   static_assert(sizeof(S) % sizeof(size_t) == 0,
 *                 "S should be a multiple of word size for efficiency");
 *
 * This macro can be used in any location where both an extern declaration and a
 * typedef could be used.
 */
#ifndef __cplusplus
   /*
    * Some of the definitions below create an otherwise-unused typedef.  This
    * triggers compiler warnings with some versions of gcc, so mark the typedefs
    * as permissibly-unused to disable the warnings.
    */
#  define MOZ_STATIC_ASSERT_GLUE1(x, y)          x##y
#  define MOZ_STATIC_ASSERT_GLUE(x, y)           MOZ_STATIC_ASSERT_GLUE1(x, y)
#  if defined(__SUNPRO_CC)
     /*
      * The Sun Studio C++ compiler is buggy when declaring, inside a function,
      * another extern'd function with an array argument whose length contains a
      * sizeof, triggering the error message "sizeof expression not accepted as
      * size of array parameter".  This bug (6688515, not public yet) would hit
      * defining moz_static_assert as a function, so we always define an extern
      * array for Sun Studio.
      *
      * We include the line number in the symbol name in a best-effort attempt
      * to avoid conflicts (see below).
      */
#    define MOZ_STATIC_ASSERT(cond, reason) \
       extern char MOZ_STATIC_ASSERT_GLUE(moz_static_assert, __LINE__)[(cond) ? 1 : -1]
#  elif defined(__COUNTER__)
     /*
      * If there was no preferred alternative, use a compiler-agnostic version.
      *
      * Note that the non-__COUNTER__ version has a bug in C++: it can't be used
      * in both |extern "C"| and normal C++ in the same translation unit.  (Alas
      * |extern "C"| isn't allowed in a function.)  The only affected compiler
      * we really care about is gcc 4.2.  For that compiler and others like it,
      * we include the line number in the function name to do the best we can to
      * avoid conflicts.  These should be rare: a conflict would require use of
      * MOZ_STATIC_ASSERT on the same line in separate files in the same
      * translation unit, *and* the uses would have to be in code with
      * different linkage, *and* the first observed use must be in C++-linkage
      * code.
      */
#    define MOZ_STATIC_ASSERT(cond, reason) \
       typedef int MOZ_STATIC_ASSERT_GLUE(moz_static_assert, __COUNTER__)[(cond) ? 1 : -1] MOZ_UNUSED_ATTRIBUTE
#  else
#    define MOZ_STATIC_ASSERT(cond, reason) \
       extern void MOZ_STATIC_ASSERT_GLUE(moz_static_assert, __LINE__)(int arg[(cond) ? 1 : -1]) MOZ_UNUSED_ATTRIBUTE
#  endif

#define MOZ_STATIC_ASSERT_IF(cond, expr, reason)  MOZ_STATIC_ASSERT(!(cond) || (expr), reason)
#else
#define MOZ_STATIC_ASSERT_IF(cond, expr, reason)  static_assert(!(cond) || (expr), reason)
#endif

MOZ_BEGIN_EXTERN_C

/*
 * Prints |aStr| as an assertion failure (using aFilename and aLine as the
 * location of the assertion) to the standard debug-output channel.
 *
 * Usually you should use MOZ_ASSERT or MOZ_CRASH instead of this method.  This
 * method is primarily for internal use in this header, and only secondarily
 * for use in implementing release-build assertions.
 */
MOZ_MAYBE_UNUSED static MOZ_COLD MOZ_NEVER_INLINE void
MOZ_ReportAssertionFailure(const char* aStr, const char* aFilename, int aLine)
  MOZ_PRETEND_NORETURN_FOR_STATIC_ANALYSIS
{
#ifdef ANDROID
  __android_log_print(ANDROID_LOG_FATAL, "MOZ_Assert",
                      "Assertion failure: %s, at %s:%d\n",
                      aStr, aFilename, aLine);
#else
  fprintf(stderr, "Assertion failure: %s, at %s:%d\n", aStr, aFilename, aLine);
#if defined (MOZ_DUMP_ASSERTION_STACK)
  nsTraceRefcnt::WalkTheStack(stderr);
#endif
  fflush(stderr);
#endif
}

MOZ_MAYBE_UNUSED static MOZ_COLD MOZ_NEVER_INLINE void
MOZ_ReportCrash(const char* aStr, const char* aFilename, int aLine)
  MOZ_PRETEND_NORETURN_FOR_STATIC_ANALYSIS
{
#ifdef ANDROID
  __android_log_print(ANDROID_LOG_FATAL, "MOZ_CRASH",
                      "Hit MOZ_CRASH(%s) at %s:%d\n", aStr, aFilename, aLine);
#else
  fprintf(stderr, "Hit MOZ_CRASH(%s) at %s:%d\n", aStr, aFilename, aLine);
#if defined(MOZ_DUMP_ASSERTION_STACK)
  nsTraceRefcnt::WalkTheStack(stderr);
#endif
  fflush(stderr);
#endif
}

/**
 * MOZ_REALLY_CRASH is used in the implementation of MOZ_CRASH().  You should
 * call MOZ_CRASH instead.
 */
#if defined(_MSC_VER)
   /*
    * On MSVC use the __debugbreak compiler intrinsic, which produces an inline
    * (not nested in a system function) breakpoint.  This distinctively invokes
    * Breakpad without requiring system library symbols on all stack-processing
    * machines, as a nested breakpoint would require.
    *
    * We use __LINE__ to prevent the compiler from folding multiple crash sites
    * together, which would make crash reports hard to understand.
    *
    * We use TerminateProcess with the exit code aborting would generate
    * because we don't want to invoke atexit handlers, destructors, library
    * unload handlers, and so on when our process might be in a compromised
    * state.
    *
    * We don't use abort() because it'd cause Windows to annoyingly pop up the
    * process error dialog multiple times.  See bug 345118 and bug 426163.
    *
    * (Technically these are Windows requirements, not MSVC requirements.  But
    * practically you need MSVC for debugging, and we only ship builds created
    * by MSVC, so doing it this way reduces complexity.)
    */

static MOZ_COLD MOZ_NORETURN MOZ_NEVER_INLINE void MOZ_NoReturn(int aLine)
{
  *((volatile int*) NULL) = aLine;
  TerminateProcess(GetCurrentProcess(), 3);
}

#  define MOZ_REALLY_CRASH(line) \
     do { \
       __debugbreak(); \
       MOZ_NoReturn(line); \
     } while (0)
#else
#  ifdef __cplusplus
#    define MOZ_REALLY_CRASH(line) \
       do { \
         *((volatile int*) NULL) = line; \
         ::abort(); \
       } while (0)
#  else
#    define MOZ_REALLY_CRASH(line) \
       do { \
         *((volatile int*) NULL) = line; \
         abort(); \
       } while (0)
#  endif
#endif

/*
 * MOZ_CRASH([explanation-string]) crashes the program, plain and simple, in a
 * Breakpad-compatible way, in both debug and release builds.
 *
 * MOZ_CRASH is a good solution for "handling" failure cases when you're
 * unwilling or unable to handle them more cleanly -- for OOM, for likely memory
 * corruption, and so on.  It's also a good solution if you need safe behavior
 * in release builds as well as debug builds.  But if the failure is one that
 * should be debugged and fixed, MOZ_ASSERT is generally preferable.
 *
 * The optional explanation-string, if provided, must be a string literal
 * explaining why we're crashing.  This argument is intended for use with
 * MOZ_CRASH() calls whose rationale is non-obvious; don't use it if it's
 * obvious why we're crashing.
 *
 * If we're a DEBUG build and we crash at a MOZ_CRASH which provides an
 * explanation-string, we print the string to stderr.  Otherwise, we don't
 * print anything; this is because we want MOZ_CRASH to be 100% safe in release
 * builds, and it's hard to print to stderr safely when memory might have been
 * corrupted.
 */
#ifndef DEBUG
#  define MOZ_CRASH(...) \
     do { \
       MOZ_CRASH_ANNOTATE("MOZ_CRASH(" __VA_ARGS__ ")"); \
       MOZ_REALLY_CRASH(__LINE__); \
     } while (0)
#else
#  define MOZ_CRASH(...) \
     do { \
       MOZ_ReportCrash("" __VA_ARGS__, __FILE__, __LINE__); \
       MOZ_CRASH_ANNOTATE("MOZ_CRASH(" __VA_ARGS__ ")"); \
       MOZ_REALLY_CRASH(__LINE__); \
     } while (0)
#endif

/*
 * MOZ_CRASH_UNSAFE_OOL(explanation-string) can be used if the explanation
 * string cannot be a string literal (but no other processing needs to be done
 * on it). A regular MOZ_CRASH() is preferred wherever possible, as passing
 * arbitrary strings from a potentially compromised process is not without risk.
 * If the string being passed is the result of a printf-style function,
 * consider using MOZ_CRASH_UNSAFE_PRINTF instead.
 *
 * @note This macro causes data collection because crash strings are annotated
 * to crash-stats and are publicly visible. Firefox data stewards must do data
 * review on usages of this macro.
 */
#ifndef DEBUG
MFBT_API MOZ_COLD MOZ_NORETURN MOZ_NEVER_INLINE void
MOZ_CrashOOL(int aLine, const char* aReason);
#  define MOZ_CRASH_UNSAFE_OOL(reason) MOZ_CrashOOL(__LINE__, reason)
#else
MFBT_API MOZ_COLD MOZ_NORETURN MOZ_NEVER_INLINE void
MOZ_CrashOOL(const char* aFilename, int aLine, const char* aReason);
#  define MOZ_CRASH_UNSAFE_OOL(reason) MOZ_CrashOOL(__FILE__, __LINE__, reason)
#endif

static const size_t sPrintfMaxArgs = 4;
static const size_t sPrintfCrashReasonSize = 1024;

#ifndef DEBUG
MFBT_API MOZ_COLD MOZ_NORETURN MOZ_NEVER_INLINE MOZ_FORMAT_PRINTF(2, 3) void
MOZ_CrashPrintf(int aLine, const char* aFormat, ...);
#  define MOZ_CALL_CRASH_PRINTF(format, ...) \
     MOZ_CrashPrintf(__LINE__, format, __VA_ARGS__)
#else
MFBT_API MOZ_COLD MOZ_NORETURN MOZ_NEVER_INLINE MOZ_FORMAT_PRINTF(3, 4) void
MOZ_CrashPrintf(const char* aFilename, int aLine, const char* aFormat, ...);
#  define MOZ_CALL_CRASH_PRINTF(format, ...) \
     MOZ_CrashPrintf(__FILE__, __LINE__, format, __VA_ARGS__)
#endif

/*
 * MOZ_CRASH_UNSAFE_PRINTF(format, arg1 [, args]) can be used when more
 * information is desired than a string literal can supply. The caller provides
 * a printf-style format string, which must be a string literal and between
 * 1 and 4 additional arguments. A regular MOZ_CRASH() is preferred wherever
 * possible, as passing arbitrary strings to printf from a potentially
 * compromised process is not without risk.
 *
 * @note This macro causes data collection because crash strings are annotated
 * to crash-stats and are publicly visible. Firefox data stewards must do data
 * review on usages of this macro.
 */
#define MOZ_CRASH_UNSAFE_PRINTF(format, ...) \
   do { \
     static_assert( \
       MOZ_ARG_COUNT(__VA_ARGS__) > 0, \
       "Did you forget arguments to MOZ_CRASH_UNSAFE_PRINTF? " \
       "Or maybe you want MOZ_CRASH instead?"); \
     static_assert( \
       MOZ_ARG_COUNT(__VA_ARGS__) <= sPrintfMaxArgs, \
       "Only up to 4 additional arguments are allowed!"); \
     static_assert(sizeof(format) <= sPrintfCrashReasonSize, \
       "The supplied format string is too long!"); \
     MOZ_CALL_CRASH_PRINTF("" format, __VA_ARGS__); \
   } while (0)

MOZ_END_EXTERN_C

/*
 * MOZ_ASSERT(expr [, explanation-string]) asserts that |expr| must be truthy in
 * debug builds.  If it is, execution continues.  Otherwise, an error message
 * including the expression and the explanation-string (if provided) is printed,
 * an attempt is made to invoke any existing debugger, and execution halts.
 * MOZ_ASSERT is fatal: no recovery is possible.  Do not assert a condition
 * which can correctly be falsy.
 *
 * The optional explanation-string, if provided, must be a string literal
 * explaining the assertion.  It is intended for use with assertions whose
 * correctness or rationale is non-obvious, and for assertions where the "real"
 * condition being tested is best described prosaically.  Don't provide an
 * explanation if it's not actually helpful.
 *
 *   // No explanation needed: pointer arguments often must not be NULL.
 *   MOZ_ASSERT(arg);
 *
 *   // An explanation can be helpful to explain exactly how we know an
 *   // assertion is valid.
 *   MOZ_ASSERT(state == WAITING_FOR_RESPONSE,
 *              "given that <thingA> and <thingB>, we must have...");
 *
 *   // Or it might disambiguate multiple identical (save for their location)
 *   // assertions of the same expression.
 *   MOZ_ASSERT(getSlot(PRIMITIVE_THIS_SLOT).isUndefined(),
 *              "we already set [[PrimitiveThis]] for this Boolean object");
 *   MOZ_ASSERT(getSlot(PRIMITIVE_THIS_SLOT).isUndefined(),
 *              "we already set [[PrimitiveThis]] for this String object");
 *
 * MOZ_ASSERT has no effect in non-debug builds.  It is designed to catch bugs
 * *only* during debugging, not "in the field". If you want the latter, use
 * MOZ_RELEASE_ASSERT, which applies to non-debug builds as well.
 *
 * MOZ_DIAGNOSTIC_ASSERT works like MOZ_RELEASE_ASSERT in Nightly/Aurora and
 * MOZ_ASSERT in Beta/Release - use this when a condition is potentially rare
 * enough to require real user testing to hit, but is not security-sensitive.
 * This can cause user pain, so use it sparingly. If a MOZ_DIAGNOSTIC_ASSERT
 * is firing, it should promptly be converted to a MOZ_ASSERT while the failure
 * is being investigated, rather than letting users suffer.
 *
 * MOZ_DIAGNOSTIC_ASSERT_ENABLED is defined when MOZ_DIAGNOSTIC_ASSERT is like
 * MOZ_RELEASE_ASSERT rather than MOZ_ASSERT.
 */

/*
 * Implement MOZ_VALIDATE_ASSERT_CONDITION_TYPE, which is used to guard against
 * accidentally passing something unintended in lieu of an assertion condition.
 */

#ifdef __cplusplus
#  include "mozilla/TypeTraits.h"
namespace mozilla {
namespace detail {

template<typename T>
struct AssertionConditionType
{
  typedef typename RemoveReference<T>::Type ValueT;
  static_assert(!IsArray<ValueT>::value,
                "Expected boolean assertion condition, got an array or a "
                "string!");
  static_assert(!IsFunction<ValueT>::value,
                "Expected boolean assertion condition, got a function! Did "
                "you intend to call that function?");
  static_assert(!IsFloatingPoint<ValueT>::value,
                "It's often a bad idea to assert that a floating-point number "
                "is nonzero, because such assertions tend to intermittently "
                "fail. Shouldn't your code gracefully handle this case instead "
                "of asserting? Anyway, if you really want to do that, write an "
                "explicit boolean condition, like !!x or x!=0.");

  static const bool isValid = true;
};

} // namespace detail
} // namespace mozilla
#  define MOZ_VALIDATE_ASSERT_CONDITION_TYPE(x) \
     static_assert(mozilla::detail::AssertionConditionType<decltype(x)>::isValid, \
                   "invalid assertion condition")
#else
#  define MOZ_VALIDATE_ASSERT_CONDITION_TYPE(x)
#endif

#if defined(DEBUG) || defined(MOZ_ASAN)
#  define MOZ_REPORT_ASSERTION_FAILURE(...) MOZ_ReportAssertionFailure(__VA_ARGS__)
#else
#  define MOZ_REPORT_ASSERTION_FAILURE(...) do { /* nothing */ } while (0)
#endif

/* First the single-argument form. */
#define MOZ_ASSERT_HELPER1(expr) \
  do { \
    MOZ_VALIDATE_ASSERT_CONDITION_TYPE(expr); \
    if (MOZ_UNLIKELY(!MOZ_CHECK_ASSERT_ASSIGNMENT(expr))) { \
      MOZ_REPORT_ASSERTION_FAILURE(#expr, __FILE__, __LINE__); \
      MOZ_CRASH_ANNOTATE("MOZ_RELEASE_ASSERT(" #expr ")"); \
      MOZ_REALLY_CRASH(__LINE__); \
    } \
  } while (0)
/* Now the two-argument form. */
#define MOZ_ASSERT_HELPER2(expr, explain) \
  do { \
    MOZ_VALIDATE_ASSERT_CONDITION_TYPE(expr); \
    if (MOZ_UNLIKELY(!MOZ_CHECK_ASSERT_ASSIGNMENT(expr))) { \
      MOZ_REPORT_ASSERTION_FAILURE(#expr " (" explain ")", __FILE__, __LINE__); \
      MOZ_CRASH_ANNOTATE("MOZ_RELEASE_ASSERT(" #expr ") (" explain ")"); \
      MOZ_REALLY_CRASH(__LINE__); \
    } \
  } while (0)

#define MOZ_RELEASE_ASSERT_GLUE(a, b) a b
#define MOZ_RELEASE_ASSERT(...) \
  MOZ_RELEASE_ASSERT_GLUE( \
    MOZ_PASTE_PREFIX_AND_ARG_COUNT(MOZ_ASSERT_HELPER, __VA_ARGS__), \
    (__VA_ARGS__))

#ifdef DEBUG
#  define MOZ_ASSERT(...) MOZ_RELEASE_ASSERT(__VA_ARGS__)
#else
#  define MOZ_ASSERT(...) do { } while (0)
#endif /* DEBUG */

#if defined(NIGHTLY_BUILD) || defined(MOZ_DEV_EDITION)
#  define MOZ_DIAGNOSTIC_ASSERT MOZ_RELEASE_ASSERT
#  define MOZ_DIAGNOSTIC_ASSERT_ENABLED 1
#else
#  define MOZ_DIAGNOSTIC_ASSERT MOZ_ASSERT
#  ifdef DEBUG
#    define MOZ_DIAGNOSTIC_ASSERT_ENABLED 1
#  endif
#endif

/*
 * MOZ_ASSERT_IF(cond1, cond2) is equivalent to MOZ_ASSERT(cond2) if cond1 is
 * true.
 *
 *   MOZ_ASSERT_IF(isPrime(num), num == 2 || isOdd(num));
 *
 * As with MOZ_ASSERT, MOZ_ASSERT_IF has effect only in debug builds.  It is
 * designed to catch bugs during debugging, not "in the field".
 */
#ifdef DEBUG
#  define MOZ_ASSERT_IF(cond, expr) \
     do { \
       if (cond) { \
         MOZ_ASSERT(expr); \
       } \
     } while (0)
#else
#  define MOZ_ASSERT_IF(cond, expr)  do { } while (0)
#endif

/*
 * MOZ_ASSUME_UNREACHABLE_MARKER() expands to an expression which states that
 * it is undefined behavior for execution to reach this point.  No guarantees
 * are made about what will happen if this is reached at runtime.  Most code
 * should use MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE because it has extra
 * asserts.
 */
#if defined(__clang__) || defined(__GNUC__)
#  define MOZ_ASSUME_UNREACHABLE_MARKER() __builtin_unreachable()
#elif defined(_MSC_VER)
#  define MOZ_ASSUME_UNREACHABLE_MARKER() __assume(0)
#else
#  ifdef __cplusplus
#    define MOZ_ASSUME_UNREACHABLE_MARKER() ::abort()
#  else
#    define MOZ_ASSUME_UNREACHABLE_MARKER() abort()
#  endif
#endif

/*
 * MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE([reason]) tells the compiler that it
 * can assume that the macro call cannot be reached during execution.  This lets
 * the compiler generate better-optimized code under some circumstances, at the
 * expense of the program's behavior being undefined if control reaches the
 * MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE.
 *
 * In Gecko, you probably should not use this macro outside of performance- or
 * size-critical code, because it's unsafe.  If you don't care about code size
 * or performance, you should probably use MOZ_ASSERT or MOZ_CRASH.
 *
 * SpiderMonkey is a different beast, and there it's acceptable to use
 * MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE more widely.
 *
 * Note that MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE is noreturn, so it's valid
 * not to return a value following a MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE
 * call.
 *
 * Example usage:
 *
 *   enum ValueType {
 *     VALUE_STRING,
 *     VALUE_INT,
 *     VALUE_FLOAT
 *   };
 *
 *   int ptrToInt(ValueType type, void* value) {
 *   {
 *     // We know for sure that type is either INT or FLOAT, and we want this
 *     // code to run as quickly as possible.
 *     switch (type) {
 *     case VALUE_INT:
 *       return *(int*) value;
 *     case VALUE_FLOAT:
 *       return (int) *(float*) value;
 *     default:
 *       MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE("Unexpected ValueType");
 *     }
 *   }
 */

/*
 * Unconditional assert in debug builds for (assumed) unreachable code paths
 * that have a safe return without crashing in release builds.
 */
#define MOZ_ASSERT_UNREACHABLE(reason) \
   MOZ_ASSERT(false, "MOZ_ASSERT_UNREACHABLE: " reason)

#define MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE(reason) \
   do { \
     MOZ_ASSERT_UNREACHABLE(reason); \
     MOZ_ASSUME_UNREACHABLE_MARKER(); \
   } while (0)

/**
 * MOZ_FALLTHROUGH_ASSERT is an annotation to suppress compiler warnings about
 * switch cases that MOZ_ASSERT(false) (or its alias MOZ_ASSERT_UNREACHABLE) in
 * debug builds, but intentionally fall through in release builds to handle
 * unexpected values.
 *
 * Why do we need MOZ_FALLTHROUGH_ASSERT in addition to MOZ_FALLTHROUGH? In
 * release builds, the MOZ_ASSERT(false) will expand to `do { } while (0)`,
 * requiring a MOZ_FALLTHROUGH annotation to suppress a -Wimplicit-fallthrough
 * warning. In debug builds, the MOZ_ASSERT(false) will expand to something like
 * `if (true) { MOZ_CRASH(); }` and the MOZ_FALLTHROUGH annotation will cause
 * a -Wunreachable-code warning. The MOZ_FALLTHROUGH_ASSERT macro breaks this
 * warning stalemate.
 *
 * // Example before MOZ_FALLTHROUGH_ASSERT:
 * switch (foo) {
 *   default:
 *     // This case wants to assert in debug builds, fall through in release.
 *     MOZ_ASSERT(false); // -Wimplicit-fallthrough warning in release builds!
 *     MOZ_FALLTHROUGH;   // but -Wunreachable-code warning in debug builds!
 *   case 5:
 *     return 5;
 * }
 *
 * // Example with MOZ_FALLTHROUGH_ASSERT:
 * switch (foo) {
 *   default:
 *     // This case asserts in debug builds, falls through in release.
 *     MOZ_FALLTHROUGH_ASSERT("Unexpected foo value?!");
 *   case 5:
 *     return 5;
 * }
 */
#ifdef DEBUG
#  define MOZ_FALLTHROUGH_ASSERT(reason) MOZ_CRASH("MOZ_FALLTHROUGH_ASSERT: " reason)
#else
#  define MOZ_FALLTHROUGH_ASSERT(...) MOZ_FALLTHROUGH
#endif

/*
 * MOZ_ALWAYS_TRUE(expr) and MOZ_ALWAYS_FALSE(expr) always evaluate the provided
 * expression, in debug builds and in release builds both.  Then, in debug
 * builds only, the value of the expression is asserted either true or false
 * using MOZ_ASSERT.
 */
#ifdef DEBUG
#  define MOZ_ALWAYS_TRUE(expr) \
     do { \
       if ((expr)) { \
         /* Do nothing. */ \
       } else { \
         MOZ_ASSERT(false, #expr); \
       } \
     } while (0)
#  define MOZ_ALWAYS_FALSE(expr) \
     do { \
       if ((expr)) { \
         MOZ_ASSERT(false, #expr); \
       } else { \
         /* Do nothing. */ \
       } \
     } while (0)
#  define MOZ_ALWAYS_OK(expr)        MOZ_ASSERT((expr).isOk())
#  define MOZ_ALWAYS_ERR(expr)       MOZ_ASSERT((expr).isErr())
#else
#  define MOZ_ALWAYS_TRUE(expr) \
     do { \
       if ((expr)) { \
          /* Silence MOZ_MUST_USE. */ \
       } \
     } while (0)
#  define MOZ_ALWAYS_FALSE(expr) \
     do { \
       if ((expr)) { \
         /* Silence MOZ_MUST_USE. */ \
       } \
     } while (0)
#  define MOZ_ALWAYS_OK(expr) \
     do { \
       if ((expr).isOk()) { \
         /* Silence MOZ_MUST_USE. */ \
       } \
     } while (0)
#  define MOZ_ALWAYS_ERR(expr) \
     do { \
       if ((expr).isErr()) { \
         /* Silence MOZ_MUST_USE. */ \
       } \
     } while (0)
#endif

#undef MOZ_DUMP_ASSERTION_STACK
#undef MOZ_CRASH_CRASHREPORT

#endif /* mozilla_Assertions_h */