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1 : /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
2 : /* vim: set ts=8 sts=2 et sw=2 tw=80: */
3 : /* This Source Code Form is subject to the terms of the Mozilla Public
4 : * License, v. 2.0. If a copy of the MPL was not distributed with this
5 : * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
6 :
7 : /* Implementations of runtime and static assertion macros for C and C++. */
8 :
9 : #ifndef mozilla_Assertions_h
10 : #define mozilla_Assertions_h
11 :
12 : #if defined(MOZILLA_INTERNAL_API) && defined(__cplusplus)
13 : #define MOZ_DUMP_ASSERTION_STACK
14 : #endif
15 :
16 : #include "mozilla/Attributes.h"
17 : #include "mozilla/Compiler.h"
18 : #include "mozilla/Likely.h"
19 : #include "mozilla/MacroArgs.h"
20 : #include "mozilla/StaticAnalysisFunctions.h"
21 : #include "mozilla/Types.h"
22 : #ifdef MOZ_DUMP_ASSERTION_STACK
23 : #include "nsTraceRefcnt.h"
24 : #endif
25 :
26 : /*
27 : * The crash reason set by MOZ_CRASH_ANNOTATE is consumed by the crash reporter
28 : * if present. It is declared here (and defined in Assertions.cpp) to make it
29 : * available to all code, even libraries that don't link with the crash reporter
30 : * directly.
31 : */
32 : MOZ_BEGIN_EXTERN_C
33 : extern MFBT_DATA const char* gMozCrashReason;
34 : MOZ_END_EXTERN_C
35 :
36 : #if !defined(DEBUG) && (defined(MOZ_HAS_MOZGLUE) || defined(MOZILLA_INTERNAL_API))
37 : static inline void
38 : AnnotateMozCrashReason(const char* reason)
39 : {
40 : gMozCrashReason = reason;
41 : }
42 : # define MOZ_CRASH_ANNOTATE(...) AnnotateMozCrashReason(__VA_ARGS__)
43 : #else
44 : # define MOZ_CRASH_ANNOTATE(...) do { /* nothing */ } while (0)
45 : #endif
46 :
47 : #include <stddef.h>
48 : #include <stdio.h>
49 : #include <stdlib.h>
50 : #ifdef _MSC_VER
51 : /*
52 : * TerminateProcess and GetCurrentProcess are defined in <winbase.h>, which
53 : * further depends on <windef.h>. We hardcode these few definitions manually
54 : * because those headers clutter the global namespace with a significant
55 : * number of undesired macros and symbols.
56 : */
57 : MOZ_BEGIN_EXTERN_C
58 : __declspec(dllimport) int __stdcall
59 : TerminateProcess(void* hProcess, unsigned int uExitCode);
60 : __declspec(dllimport) void* __stdcall GetCurrentProcess(void);
61 : MOZ_END_EXTERN_C
62 : #else
63 : # include <signal.h>
64 : #endif
65 : #ifdef ANDROID
66 : # include <android/log.h>
67 : #endif
68 :
69 : /*
70 : * MOZ_STATIC_ASSERT may be used to assert a condition *at compile time* in C.
71 : * In C++11, static_assert is provided by the compiler to the same effect.
72 : * This can be useful when you make certain assumptions about what must hold for
73 : * optimal, or even correct, behavior. For example, you might assert that the
74 : * size of a struct is a multiple of the target architecture's word size:
75 : *
76 : * struct S { ... };
77 : * // C
78 : * MOZ_STATIC_ASSERT(sizeof(S) % sizeof(size_t) == 0,
79 : * "S should be a multiple of word size for efficiency");
80 : * // C++11
81 : * static_assert(sizeof(S) % sizeof(size_t) == 0,
82 : * "S should be a multiple of word size for efficiency");
83 : *
84 : * This macro can be used in any location where both an extern declaration and a
85 : * typedef could be used.
86 : */
87 : #ifndef __cplusplus
88 : /*
89 : * Some of the definitions below create an otherwise-unused typedef. This
90 : * triggers compiler warnings with some versions of gcc, so mark the typedefs
91 : * as permissibly-unused to disable the warnings.
92 : */
93 : # if defined(__GNUC__)
94 : # define MOZ_STATIC_ASSERT_UNUSED_ATTRIBUTE __attribute__((unused))
95 : # else
96 : # define MOZ_STATIC_ASSERT_UNUSED_ATTRIBUTE /* nothing */
97 : # endif
98 : # define MOZ_STATIC_ASSERT_GLUE1(x, y) x##y
99 : # define MOZ_STATIC_ASSERT_GLUE(x, y) MOZ_STATIC_ASSERT_GLUE1(x, y)
100 : # if defined(__SUNPRO_CC)
101 : /*
102 : * The Sun Studio C++ compiler is buggy when declaring, inside a function,
103 : * another extern'd function with an array argument whose length contains a
104 : * sizeof, triggering the error message "sizeof expression not accepted as
105 : * size of array parameter". This bug (6688515, not public yet) would hit
106 : * defining moz_static_assert as a function, so we always define an extern
107 : * array for Sun Studio.
108 : *
109 : * We include the line number in the symbol name in a best-effort attempt
110 : * to avoid conflicts (see below).
111 : */
112 : # define MOZ_STATIC_ASSERT(cond, reason) \
113 : extern char MOZ_STATIC_ASSERT_GLUE(moz_static_assert, __LINE__)[(cond) ? 1 : -1]
114 : # elif defined(__COUNTER__)
115 : /*
116 : * If there was no preferred alternative, use a compiler-agnostic version.
117 : *
118 : * Note that the non-__COUNTER__ version has a bug in C++: it can't be used
119 : * in both |extern "C"| and normal C++ in the same translation unit. (Alas
120 : * |extern "C"| isn't allowed in a function.) The only affected compiler
121 : * we really care about is gcc 4.2. For that compiler and others like it,
122 : * we include the line number in the function name to do the best we can to
123 : * avoid conflicts. These should be rare: a conflict would require use of
124 : * MOZ_STATIC_ASSERT on the same line in separate files in the same
125 : * translation unit, *and* the uses would have to be in code with
126 : * different linkage, *and* the first observed use must be in C++-linkage
127 : * code.
128 : */
129 : # define MOZ_STATIC_ASSERT(cond, reason) \
130 : typedef int MOZ_STATIC_ASSERT_GLUE(moz_static_assert, __COUNTER__)[(cond) ? 1 : -1] MOZ_STATIC_ASSERT_UNUSED_ATTRIBUTE
131 : # else
132 : # define MOZ_STATIC_ASSERT(cond, reason) \
133 : extern void MOZ_STATIC_ASSERT_GLUE(moz_static_assert, __LINE__)(int arg[(cond) ? 1 : -1]) MOZ_STATIC_ASSERT_UNUSED_ATTRIBUTE
134 : # endif
135 :
136 : #define MOZ_STATIC_ASSERT_IF(cond, expr, reason) MOZ_STATIC_ASSERT(!(cond) || (expr), reason)
137 : #else
138 : #define MOZ_STATIC_ASSERT_IF(cond, expr, reason) static_assert(!(cond) || (expr), reason)
139 : #endif
140 :
141 : MOZ_BEGIN_EXTERN_C
142 :
143 : /*
144 : * Prints |aStr| as an assertion failure (using aFilename and aLine as the
145 : * location of the assertion) to the standard debug-output channel.
146 : *
147 : * Usually you should use MOZ_ASSERT or MOZ_CRASH instead of this method. This
148 : * method is primarily for internal use in this header, and only secondarily
149 : * for use in implementing release-build assertions.
150 : */
151 : MOZ_MAYBE_UNUSED static MOZ_COLD MOZ_NEVER_INLINE void
152 0 : MOZ_ReportAssertionFailure(const char* aStr, const char* aFilename, int aLine)
153 : MOZ_PRETEND_NORETURN_FOR_STATIC_ANALYSIS
154 : {
155 : #ifdef ANDROID
156 : __android_log_print(ANDROID_LOG_FATAL, "MOZ_Assert",
157 : "Assertion failure: %s, at %s:%d\n",
158 : aStr, aFilename, aLine);
159 : #else
160 0 : fprintf(stderr, "Assertion failure: %s, at %s:%d\n", aStr, aFilename, aLine);
161 : #if defined (MOZ_DUMP_ASSERTION_STACK)
162 0 : nsTraceRefcnt::WalkTheStack(stderr);
163 : #endif
164 0 : fflush(stderr);
165 : #endif
166 0 : }
167 :
168 : MOZ_MAYBE_UNUSED static MOZ_COLD MOZ_NEVER_INLINE void
169 0 : MOZ_ReportCrash(const char* aStr, const char* aFilename, int aLine)
170 : MOZ_PRETEND_NORETURN_FOR_STATIC_ANALYSIS
171 : {
172 : #ifdef ANDROID
173 : __android_log_print(ANDROID_LOG_FATAL, "MOZ_CRASH",
174 : "Hit MOZ_CRASH(%s) at %s:%d\n", aStr, aFilename, aLine);
175 : #else
176 0 : fprintf(stderr, "Hit MOZ_CRASH(%s) at %s:%d\n", aStr, aFilename, aLine);
177 : #if defined(MOZ_DUMP_ASSERTION_STACK)
178 0 : nsTraceRefcnt::WalkTheStack(stderr);
179 : #endif
180 0 : fflush(stderr);
181 : #endif
182 0 : }
183 :
184 : /**
185 : * MOZ_REALLY_CRASH is used in the implementation of MOZ_CRASH(). You should
186 : * call MOZ_CRASH instead.
187 : */
188 : #if defined(_MSC_VER)
189 : /*
190 : * On MSVC use the __debugbreak compiler intrinsic, which produces an inline
191 : * (not nested in a system function) breakpoint. This distinctively invokes
192 : * Breakpad without requiring system library symbols on all stack-processing
193 : * machines, as a nested breakpoint would require.
194 : *
195 : * We use __LINE__ to prevent the compiler from folding multiple crash sites
196 : * together, which would make crash reports hard to understand.
197 : *
198 : * We use TerminateProcess with the exit code aborting would generate
199 : * because we don't want to invoke atexit handlers, destructors, library
200 : * unload handlers, and so on when our process might be in a compromised
201 : * state.
202 : *
203 : * We don't use abort() because it'd cause Windows to annoyingly pop up the
204 : * process error dialog multiple times. See bug 345118 and bug 426163.
205 : *
206 : * (Technically these are Windows requirements, not MSVC requirements. But
207 : * practically you need MSVC for debugging, and we only ship builds created
208 : * by MSVC, so doing it this way reduces complexity.)
209 : */
210 :
211 : static MOZ_COLD MOZ_NORETURN MOZ_NEVER_INLINE void MOZ_NoReturn(int aLine)
212 : {
213 : *((volatile int*) NULL) = aLine;
214 : TerminateProcess(GetCurrentProcess(), 3);
215 : }
216 :
217 : # define MOZ_REALLY_CRASH(line) \
218 : do { \
219 : __debugbreak(); \
220 : MOZ_NoReturn(line); \
221 : } while (0)
222 : #else
223 : # ifdef __cplusplus
224 : # define MOZ_REALLY_CRASH(line) \
225 : do { \
226 : *((volatile int*) NULL) = line; \
227 : ::abort(); \
228 : } while (0)
229 : # else
230 : # define MOZ_REALLY_CRASH(line) \
231 : do { \
232 : *((volatile int*) NULL) = line; \
233 : abort(); \
234 : } while (0)
235 : # endif
236 : #endif
237 :
238 : /*
239 : * MOZ_CRASH([explanation-string]) crashes the program, plain and simple, in a
240 : * Breakpad-compatible way, in both debug and release builds.
241 : *
242 : * MOZ_CRASH is a good solution for "handling" failure cases when you're
243 : * unwilling or unable to handle them more cleanly -- for OOM, for likely memory
244 : * corruption, and so on. It's also a good solution if you need safe behavior
245 : * in release builds as well as debug builds. But if the failure is one that
246 : * should be debugged and fixed, MOZ_ASSERT is generally preferable.
247 : *
248 : * The optional explanation-string, if provided, must be a string literal
249 : * explaining why we're crashing. This argument is intended for use with
250 : * MOZ_CRASH() calls whose rationale is non-obvious; don't use it if it's
251 : * obvious why we're crashing.
252 : *
253 : * If we're a DEBUG build and we crash at a MOZ_CRASH which provides an
254 : * explanation-string, we print the string to stderr. Otherwise, we don't
255 : * print anything; this is because we want MOZ_CRASH to be 100% safe in release
256 : * builds, and it's hard to print to stderr safely when memory might have been
257 : * corrupted.
258 : */
259 : #ifndef DEBUG
260 : # define MOZ_CRASH(...) \
261 : do { \
262 : MOZ_CRASH_ANNOTATE("MOZ_CRASH(" __VA_ARGS__ ")"); \
263 : MOZ_REALLY_CRASH(__LINE__); \
264 : } while (0)
265 : #else
266 : # define MOZ_CRASH(...) \
267 : do { \
268 : MOZ_ReportCrash("" __VA_ARGS__, __FILE__, __LINE__); \
269 : MOZ_CRASH_ANNOTATE("MOZ_CRASH(" __VA_ARGS__ ")"); \
270 : MOZ_REALLY_CRASH(__LINE__); \
271 : } while (0)
272 : #endif
273 :
274 : /*
275 : * MOZ_CRASH_UNSAFE_OOL(explanation-string) can be used if the explanation
276 : * string cannot be a string literal (but no other processing needs to be done
277 : * on it). A regular MOZ_CRASH() is preferred wherever possible, as passing
278 : * arbitrary strings from a potentially compromised process is not without risk.
279 : * If the string being passed is the result of a printf-style function,
280 : * consider using MOZ_CRASH_UNSAFE_PRINTF instead.
281 : */
282 : #ifndef DEBUG
283 : MFBT_API MOZ_COLD MOZ_NORETURN MOZ_NEVER_INLINE void
284 : MOZ_CrashOOL(int aLine, const char* aReason);
285 : # define MOZ_CRASH_UNSAFE_OOL(reason) MOZ_CrashOOL(__LINE__, reason)
286 : #else
287 : MFBT_API MOZ_COLD MOZ_NORETURN MOZ_NEVER_INLINE void
288 : MOZ_CrashOOL(const char* aFilename, int aLine, const char* aReason);
289 : # define MOZ_CRASH_UNSAFE_OOL(reason) MOZ_CrashOOL(__FILE__, __LINE__, reason)
290 : #endif
291 :
292 : static const size_t sPrintfMaxArgs = 4;
293 : static const size_t sPrintfCrashReasonSize = 1024;
294 :
295 : #ifndef DEBUG
296 : MFBT_API MOZ_COLD MOZ_NORETURN MOZ_NEVER_INLINE MOZ_FORMAT_PRINTF(2, 3) void
297 : MOZ_CrashPrintf(int aLine, const char* aFormat, ...);
298 : # define MOZ_CALL_CRASH_PRINTF(format, ...) \
299 : MOZ_CrashPrintf(__LINE__, format, __VA_ARGS__)
300 : #else
301 : MFBT_API MOZ_COLD MOZ_NORETURN MOZ_NEVER_INLINE MOZ_FORMAT_PRINTF(3, 4) void
302 : MOZ_CrashPrintf(const char* aFilename, int aLine, const char* aFormat, ...);
303 : # define MOZ_CALL_CRASH_PRINTF(format, ...) \
304 : MOZ_CrashPrintf(__FILE__, __LINE__, format, __VA_ARGS__)
305 : #endif
306 :
307 : /*
308 : * MOZ_CRASH_UNSAFE_PRINTF(format, arg1 [, args]) can be used when more
309 : * information is desired than a string literal can supply. The caller provides
310 : * a printf-style format string, which must be a string literal and between
311 : * 1 and 4 additional arguments. A regular MOZ_CRASH() is preferred wherever
312 : * possible, as passing arbitrary strings to printf from a potentially
313 : * compromised process is not without risk.
314 : */
315 : #define MOZ_CRASH_UNSAFE_PRINTF(format, ...) \
316 : do { \
317 : static_assert( \
318 : MOZ_ARG_COUNT(__VA_ARGS__) > 0, \
319 : "Did you forget arguments to MOZ_CRASH_UNSAFE_PRINTF? " \
320 : "Or maybe you want MOZ_CRASH instead?"); \
321 : static_assert( \
322 : MOZ_ARG_COUNT(__VA_ARGS__) <= sPrintfMaxArgs, \
323 : "Only up to 4 additional arguments are allowed!"); \
324 : static_assert(sizeof(format) <= sPrintfCrashReasonSize, \
325 : "The supplied format string is too long!"); \
326 : MOZ_CALL_CRASH_PRINTF("" format, __VA_ARGS__); \
327 : } while (0)
328 :
329 : MOZ_END_EXTERN_C
330 :
331 : /*
332 : * MOZ_ASSERT(expr [, explanation-string]) asserts that |expr| must be truthy in
333 : * debug builds. If it is, execution continues. Otherwise, an error message
334 : * including the expression and the explanation-string (if provided) is printed,
335 : * an attempt is made to invoke any existing debugger, and execution halts.
336 : * MOZ_ASSERT is fatal: no recovery is possible. Do not assert a condition
337 : * which can correctly be falsy.
338 : *
339 : * The optional explanation-string, if provided, must be a string literal
340 : * explaining the assertion. It is intended for use with assertions whose
341 : * correctness or rationale is non-obvious, and for assertions where the "real"
342 : * condition being tested is best described prosaically. Don't provide an
343 : * explanation if it's not actually helpful.
344 : *
345 : * // No explanation needed: pointer arguments often must not be NULL.
346 : * MOZ_ASSERT(arg);
347 : *
348 : * // An explanation can be helpful to explain exactly how we know an
349 : * // assertion is valid.
350 : * MOZ_ASSERT(state == WAITING_FOR_RESPONSE,
351 : * "given that <thingA> and <thingB>, we must have...");
352 : *
353 : * // Or it might disambiguate multiple identical (save for their location)
354 : * // assertions of the same expression.
355 : * MOZ_ASSERT(getSlot(PRIMITIVE_THIS_SLOT).isUndefined(),
356 : * "we already set [[PrimitiveThis]] for this Boolean object");
357 : * MOZ_ASSERT(getSlot(PRIMITIVE_THIS_SLOT).isUndefined(),
358 : * "we already set [[PrimitiveThis]] for this String object");
359 : *
360 : * MOZ_ASSERT has no effect in non-debug builds. It is designed to catch bugs
361 : * *only* during debugging, not "in the field". If you want the latter, use
362 : * MOZ_RELEASE_ASSERT, which applies to non-debug builds as well.
363 : *
364 : * MOZ_DIAGNOSTIC_ASSERT works like MOZ_RELEASE_ASSERT in Nightly/Aurora and
365 : * MOZ_ASSERT in Beta/Release - use this when a condition is potentially rare
366 : * enough to require real user testing to hit, but is not security-sensitive.
367 : * This can cause user pain, so use it sparingly. If a MOZ_DIAGNOSTIC_ASSERT
368 : * is firing, it should promptly be converted to a MOZ_ASSERT while the failure
369 : * is being investigated, rather than letting users suffer.
370 : *
371 : * MOZ_DIAGNOSTIC_ASSERT_ENABLED is defined when MOZ_DIAGNOSTIC_ASSERT is like
372 : * MOZ_RELEASE_ASSERT rather than MOZ_ASSERT.
373 : */
374 :
375 : /*
376 : * Implement MOZ_VALIDATE_ASSERT_CONDITION_TYPE, which is used to guard against
377 : * accidentally passing something unintended in lieu of an assertion condition.
378 : */
379 :
380 : #ifdef __cplusplus
381 : # include "mozilla/TypeTraits.h"
382 : namespace mozilla {
383 : namespace detail {
384 :
385 : template<typename T>
386 : struct AssertionConditionType
387 : {
388 : typedef typename RemoveReference<T>::Type ValueT;
389 : static_assert(!IsArray<ValueT>::value,
390 : "Expected boolean assertion condition, got an array or a "
391 : "string!");
392 : static_assert(!IsFunction<ValueT>::value,
393 : "Expected boolean assertion condition, got a function! Did "
394 : "you intend to call that function?");
395 : static_assert(!IsFloatingPoint<ValueT>::value,
396 : "It's often a bad idea to assert that a floating-point number "
397 : "is nonzero, because such assertions tend to intermittently "
398 : "fail. Shouldn't your code gracefully handle this case instead "
399 : "of asserting? Anyway, if you really want to do that, write an "
400 : "explicit boolean condition, like !!x or x!=0.");
401 :
402 : static const bool isValid = true;
403 : };
404 :
405 : } // namespace detail
406 : } // namespace mozilla
407 : # define MOZ_VALIDATE_ASSERT_CONDITION_TYPE(x) \
408 : static_assert(mozilla::detail::AssertionConditionType<decltype(x)>::isValid, \
409 : "invalid assertion condition")
410 : #else
411 : # define MOZ_VALIDATE_ASSERT_CONDITION_TYPE(x)
412 : #endif
413 :
414 : #if defined(DEBUG) || defined(MOZ_ASAN)
415 : # define MOZ_REPORT_ASSERTION_FAILURE(...) MOZ_ReportAssertionFailure(__VA_ARGS__)
416 : #else
417 : # define MOZ_REPORT_ASSERTION_FAILURE(...) do { /* nothing */ } while (0)
418 : #endif
419 :
420 : /* First the single-argument form. */
421 : #define MOZ_ASSERT_HELPER1(expr) \
422 : do { \
423 : MOZ_VALIDATE_ASSERT_CONDITION_TYPE(expr); \
424 : if (MOZ_UNLIKELY(!MOZ_CHECK_ASSERT_ASSIGNMENT(expr))) { \
425 : MOZ_REPORT_ASSERTION_FAILURE(#expr, __FILE__, __LINE__); \
426 : MOZ_CRASH_ANNOTATE("MOZ_RELEASE_ASSERT(" #expr ")"); \
427 : MOZ_REALLY_CRASH(__LINE__); \
428 : } \
429 : } while (0)
430 : /* Now the two-argument form. */
431 : #define MOZ_ASSERT_HELPER2(expr, explain) \
432 : do { \
433 : MOZ_VALIDATE_ASSERT_CONDITION_TYPE(expr); \
434 : if (MOZ_UNLIKELY(!MOZ_CHECK_ASSERT_ASSIGNMENT(expr))) { \
435 : MOZ_REPORT_ASSERTION_FAILURE(#expr " (" explain ")", __FILE__, __LINE__); \
436 : MOZ_CRASH_ANNOTATE("MOZ_RELEASE_ASSERT(" #expr ") (" explain ")"); \
437 : MOZ_REALLY_CRASH(__LINE__); \
438 : } \
439 : } while (0)
440 :
441 : #define MOZ_RELEASE_ASSERT_GLUE(a, b) a b
442 : #define MOZ_RELEASE_ASSERT(...) \
443 : MOZ_RELEASE_ASSERT_GLUE( \
444 : MOZ_PASTE_PREFIX_AND_ARG_COUNT(MOZ_ASSERT_HELPER, __VA_ARGS__), \
445 : (__VA_ARGS__))
446 :
447 : #ifdef DEBUG
448 : # define MOZ_ASSERT(...) MOZ_RELEASE_ASSERT(__VA_ARGS__)
449 : #else
450 : # define MOZ_ASSERT(...) do { } while (0)
451 : #endif /* DEBUG */
452 :
453 : #if defined(NIGHTLY_BUILD) || defined(MOZ_DEV_EDITION)
454 : # define MOZ_DIAGNOSTIC_ASSERT MOZ_RELEASE_ASSERT
455 : # define MOZ_DIAGNOSTIC_ASSERT_ENABLED 1
456 : #else
457 : # define MOZ_DIAGNOSTIC_ASSERT MOZ_ASSERT
458 : # ifdef DEBUG
459 : # define MOZ_DIAGNOSTIC_ASSERT_ENABLED 1
460 : # endif
461 : #endif
462 :
463 : /*
464 : * MOZ_ASSERT_IF(cond1, cond2) is equivalent to MOZ_ASSERT(cond2) if cond1 is
465 : * true.
466 : *
467 : * MOZ_ASSERT_IF(isPrime(num), num == 2 || isOdd(num));
468 : *
469 : * As with MOZ_ASSERT, MOZ_ASSERT_IF has effect only in debug builds. It is
470 : * designed to catch bugs during debugging, not "in the field".
471 : */
472 : #ifdef DEBUG
473 : # define MOZ_ASSERT_IF(cond, expr) \
474 : do { \
475 : if (cond) { \
476 : MOZ_ASSERT(expr); \
477 : } \
478 : } while (0)
479 : #else
480 : # define MOZ_ASSERT_IF(cond, expr) do { } while (0)
481 : #endif
482 :
483 : /*
484 : * MOZ_ASSUME_UNREACHABLE_MARKER() expands to an expression which states that
485 : * it is undefined behavior for execution to reach this point. No guarantees
486 : * are made about what will happen if this is reached at runtime. Most code
487 : * should use MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE because it has extra
488 : * asserts.
489 : */
490 : #if defined(__clang__) || defined(__GNUC__)
491 : # define MOZ_ASSUME_UNREACHABLE_MARKER() __builtin_unreachable()
492 : #elif defined(_MSC_VER)
493 : # define MOZ_ASSUME_UNREACHABLE_MARKER() __assume(0)
494 : #else
495 : # ifdef __cplusplus
496 : # define MOZ_ASSUME_UNREACHABLE_MARKER() ::abort()
497 : # else
498 : # define MOZ_ASSUME_UNREACHABLE_MARKER() abort()
499 : # endif
500 : #endif
501 :
502 : /*
503 : * MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE([reason]) tells the compiler that it
504 : * can assume that the macro call cannot be reached during execution. This lets
505 : * the compiler generate better-optimized code under some circumstances, at the
506 : * expense of the program's behavior being undefined if control reaches the
507 : * MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE.
508 : *
509 : * In Gecko, you probably should not use this macro outside of performance- or
510 : * size-critical code, because it's unsafe. If you don't care about code size
511 : * or performance, you should probably use MOZ_ASSERT or MOZ_CRASH.
512 : *
513 : * SpiderMonkey is a different beast, and there it's acceptable to use
514 : * MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE more widely.
515 : *
516 : * Note that MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE is noreturn, so it's valid
517 : * not to return a value following a MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE
518 : * call.
519 : *
520 : * Example usage:
521 : *
522 : * enum ValueType {
523 : * VALUE_STRING,
524 : * VALUE_INT,
525 : * VALUE_FLOAT
526 : * };
527 : *
528 : * int ptrToInt(ValueType type, void* value) {
529 : * {
530 : * // We know for sure that type is either INT or FLOAT, and we want this
531 : * // code to run as quickly as possible.
532 : * switch (type) {
533 : * case VALUE_INT:
534 : * return *(int*) value;
535 : * case VALUE_FLOAT:
536 : * return (int) *(float*) value;
537 : * default:
538 : * MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE("Unexpected ValueType");
539 : * }
540 : * }
541 : */
542 :
543 : /*
544 : * Unconditional assert in debug builds for (assumed) unreachable code paths
545 : * that have a safe return without crashing in release builds.
546 : */
547 : #define MOZ_ASSERT_UNREACHABLE(reason) \
548 : MOZ_ASSERT(false, "MOZ_ASSERT_UNREACHABLE: " reason)
549 :
550 : #define MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE(reason) \
551 : do { \
552 : MOZ_ASSERT_UNREACHABLE(reason); \
553 : MOZ_ASSUME_UNREACHABLE_MARKER(); \
554 : } while (0)
555 :
556 : /**
557 : * MOZ_FALLTHROUGH_ASSERT is an annotation to suppress compiler warnings about
558 : * switch cases that MOZ_ASSERT(false) (or its alias MOZ_ASSERT_UNREACHABLE) in
559 : * debug builds, but intentionally fall through in release builds to handle
560 : * unexpected values.
561 : *
562 : * Why do we need MOZ_FALLTHROUGH_ASSERT in addition to MOZ_FALLTHROUGH? In
563 : * release builds, the MOZ_ASSERT(false) will expand to `do { } while (0)`,
564 : * requiring a MOZ_FALLTHROUGH annotation to suppress a -Wimplicit-fallthrough
565 : * warning. In debug builds, the MOZ_ASSERT(false) will expand to something like
566 : * `if (true) { MOZ_CRASH(); }` and the MOZ_FALLTHROUGH annotation will cause
567 : * a -Wunreachable-code warning. The MOZ_FALLTHROUGH_ASSERT macro breaks this
568 : * warning stalemate.
569 : *
570 : * // Example before MOZ_FALLTHROUGH_ASSERT:
571 : * switch (foo) {
572 : * default:
573 : * // This case wants to assert in debug builds, fall through in release.
574 : * MOZ_ASSERT(false); // -Wimplicit-fallthrough warning in release builds!
575 : * MOZ_FALLTHROUGH; // but -Wunreachable-code warning in debug builds!
576 : * case 5:
577 : * return 5;
578 : * }
579 : *
580 : * // Example with MOZ_FALLTHROUGH_ASSERT:
581 : * switch (foo) {
582 : * default:
583 : * // This case asserts in debug builds, falls through in release.
584 : * MOZ_FALLTHROUGH_ASSERT("Unexpected foo value?!");
585 : * case 5:
586 : * return 5;
587 : * }
588 : */
589 : #ifdef DEBUG
590 : # define MOZ_FALLTHROUGH_ASSERT(reason) MOZ_CRASH("MOZ_FALLTHROUGH_ASSERT: " reason)
591 : #else
592 : # define MOZ_FALLTHROUGH_ASSERT(...) MOZ_FALLTHROUGH
593 : #endif
594 :
595 : /*
596 : * MOZ_ALWAYS_TRUE(expr) and MOZ_ALWAYS_FALSE(expr) always evaluate the provided
597 : * expression, in debug builds and in release builds both. Then, in debug
598 : * builds only, the value of the expression is asserted either true or false
599 : * using MOZ_ASSERT.
600 : */
601 : #ifdef DEBUG
602 : # define MOZ_ALWAYS_TRUE(expr) \
603 : do { \
604 : if ((expr)) { \
605 : /* Do nothing. */ \
606 : } else { \
607 : MOZ_ASSERT(false, #expr); \
608 : } \
609 : } while (0)
610 : # define MOZ_ALWAYS_FALSE(expr) \
611 : do { \
612 : if ((expr)) { \
613 : MOZ_ASSERT(false, #expr); \
614 : } else { \
615 : /* Do nothing. */ \
616 : } \
617 : } while (0)
618 : # define MOZ_ALWAYS_OK(expr) MOZ_ASSERT((expr).isOk())
619 : # define MOZ_ALWAYS_ERR(expr) MOZ_ASSERT((expr).isErr())
620 : #else
621 : # define MOZ_ALWAYS_TRUE(expr) \
622 : do { \
623 : if ((expr)) { \
624 : /* Silence MOZ_MUST_USE. */ \
625 : } \
626 : } while (0)
627 : # define MOZ_ALWAYS_FALSE(expr) \
628 : do { \
629 : if ((expr)) { \
630 : /* Silence MOZ_MUST_USE. */ \
631 : } \
632 : } while (0)
633 : # define MOZ_ALWAYS_OK(expr) \
634 : do { \
635 : if ((expr).isOk()) { \
636 : /* Silence MOZ_MUST_USE. */ \
637 : } \
638 : } while (0)
639 : # define MOZ_ALWAYS_ERR(expr) \
640 : do { \
641 : if ((expr).isErr()) { \
642 : /* Silence MOZ_MUST_USE. */ \
643 : } \
644 : } while (0)
645 : #endif
646 :
647 : #undef MOZ_DUMP_ASSERTION_STACK
648 : #undef MOZ_CRASH_CRASHREPORT
649 :
650 : #endif /* mozilla_Assertions_h */
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