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 #ifdef MOZ_DUMP_ASSERTION_STACK
21 #include "nsTraceRefcnt.h"
22 #endif
23
24 #if defined(MOZ_CRASHREPORTER) && defined(MOZILLA_INTERNAL_API) && \
25 !defined(MOZILLA_EXTERNAL_LINKAGE) && defined(__cplusplus)
26 namespace CrashReporter {
27 // This declaration is present here as well as in nsExceptionHandler.h
28 // nsExceptionHandler.h is not directly included in this file as it includes
29 // windows.h, which can cause problems when it is imported into some files due
30 // to the number of macros defined.
31 // XXX If you change this definition - also change the definition in
32 // nsExceptionHandler.h
33 void AnnotateMozCrashReason(const char* aReason);
34 } // namespace CrashReporter
35
36 # define MOZ_CRASH_ANNOTATE(...) CrashReporter::AnnotateMozCrashReason("" __VA_ARGS__)
37 #else
38 # define MOZ_CRASH_ANNOTATE(...) do { /* nothing */ } while (0)
39 #endif
40
41 #include <stddef.h>
42 #include <stdio.h>
43 #include <stdlib.h>
44 #ifdef WIN32
45 /*
46 * TerminateProcess and GetCurrentProcess are defined in <winbase.h>, which
47 * further depends on <windef.h>. We hardcode these few definitions manually
48 * because those headers clutter the global namespace with a significant
49 * number of undesired macros and symbols.
50 */
51 # ifdef __cplusplus
52 extern "C" {
53 # endif
54 __declspec(dllimport) int __stdcall
55 TerminateProcess(void* hProcess, unsigned int uExitCode);
56 __declspec(dllimport) void* __stdcall GetCurrentProcess(void);
57 # ifdef __cplusplus
58 }
59 # endif
60 #else
61 # include <signal.h>
62 #endif
63 #ifdef ANDROID
64 # include <android/log.h>
65 #endif
66
67 /*
68 * MOZ_STATIC_ASSERT may be used to assert a condition *at compile time* in C.
69 * In C++11, static_assert is provided by the compiler to the same effect.
70 * This can be useful when you make certain assumptions about what must hold for
71 * optimal, or even correct, behavior. For example, you might assert that the
72 * size of a struct is a multiple of the target architecture's word size:
73 *
74 * struct S { ... };
75 * // C
76 * MOZ_STATIC_ASSERT(sizeof(S) % sizeof(size_t) == 0,
77 * "S should be a multiple of word size for efficiency");
78 * // C++11
79 * static_assert(sizeof(S) % sizeof(size_t) == 0,
80 * "S should be a multiple of word size for efficiency");
81 *
82 * This macro can be used in any location where both an extern declaration and a
83 * typedef could be used.
84 */
85 #ifndef __cplusplus
86 /*
87 * Some of the definitions below create an otherwise-unused typedef. This
88 * triggers compiler warnings with some versions of gcc, so mark the typedefs
89 * as permissibly-unused to disable the warnings.
90 */
91 # if defined(__GNUC__)
92 # define MOZ_STATIC_ASSERT_UNUSED_ATTRIBUTE __attribute__((unused))
93 # else
94 # define MOZ_STATIC_ASSERT_UNUSED_ATTRIBUTE /* nothing */
95 # endif
96 # define MOZ_STATIC_ASSERT_GLUE1(x, y) x##y
97 # define MOZ_STATIC_ASSERT_GLUE(x, y) MOZ_STATIC_ASSERT_GLUE1(x, y)
98 # if defined(__SUNPRO_CC)
99 /*
100 * The Sun Studio C++ compiler is buggy when declaring, inside a function,
101 * another extern'd function with an array argument whose length contains a
102 * sizeof, triggering the error message "sizeof expression not accepted as
103 * size of array parameter". This bug (6688515, not public yet) would hit
104 * defining moz_static_assert as a function, so we always define an extern
105 * array for Sun Studio.
106 *
107 * We include the line number in the symbol name in a best-effort attempt
108 * to avoid conflicts (see below).
109 */
110 # define MOZ_STATIC_ASSERT(cond, reason) \
111 extern char MOZ_STATIC_ASSERT_GLUE(moz_static_assert, __LINE__)[(cond) ? 1 : -1]
112 # elif defined(__COUNTER__)
113 /*
114 * If there was no preferred alternative, use a compiler-agnostic version.
115 *
116 * Note that the non-__COUNTER__ version has a bug in C++: it can't be used
117 * in both |extern "C"| and normal C++ in the same translation unit. (Alas
118 * |extern "C"| isn't allowed in a function.) The only affected compiler
119 * we really care about is gcc 4.2. For that compiler and others like it,
120 * we include the line number in the function name to do the best we can to
121 * avoid conflicts. These should be rare: a conflict would require use of
122 * MOZ_STATIC_ASSERT on the same line in separate files in the same
123 * translation unit, *and* the uses would have to be in code with
124 * different linkage, *and* the first observed use must be in C++-linkage
125 * code.
126 */
127 # define MOZ_STATIC_ASSERT(cond, reason) \
128 typedef int MOZ_STATIC_ASSERT_GLUE(moz_static_assert, __COUNTER__)[(cond) ? 1 : -1] MOZ_STATIC_ASSERT_UNUSED_ATTRIBUTE
129 # else
130 # define MOZ_STATIC_ASSERT(cond, reason) \
131 extern void MOZ_STATIC_ASSERT_GLUE(moz_static_assert, __LINE__)(int arg[(cond) ? 1 : -1]) MOZ_STATIC_ASSERT_UNUSED_ATTRIBUTE
132 # endif
133
134 #define MOZ_STATIC_ASSERT_IF(cond, expr, reason) MOZ_STATIC_ASSERT(!(cond) || (expr), reason)
135 #else
136 #define MOZ_STATIC_ASSERT_IF(cond, expr, reason) static_assert(!(cond) || (expr), reason)
137 #endif
138
139 #ifdef __cplusplus
140 extern "C" {
141 #endif
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 static MOZ_COLD MOZ_ALWAYS_INLINE void
MOZ_ReportAssertionFailure(const char * aStr,const char * aFilename,int aLine)152 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 fprintf(stderr, "Assertion failure: %s, at %s:%d\n", aStr, aFilename, aLine);
161 #if defined (MOZ_DUMP_ASSERTION_STACK) && !defined(MOZILLA_XPCOMRT_API)
162 nsTraceRefcnt::WalkTheStack(stderr);
163 #endif
164 fflush(stderr);
165 #endif
166 }
167
168 static MOZ_COLD MOZ_ALWAYS_INLINE void
MOZ_ReportCrash(const char * aStr,const char * aFilename,int aLine)169 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 fprintf(stderr, "Hit MOZ_CRASH(%s) at %s:%d\n", aStr, aFilename, aLine);
177 #if defined(MOZ_DUMP_ASSERTION_STACK) && !defined(MOZILLA_XPCOMRT_API)
178 nsTraceRefcnt::WalkTheStack(stderr);
179 #endif
180 fflush(stderr);
181 #endif
182 }
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 TerminateProcess with the exit code aborting would generate
196 * because we don't want to invoke atexit handlers, destructors, library
197 * unload handlers, and so on when our process might be in a compromised
198 * state.
199 *
200 * We don't use abort() because it'd cause Windows to annoyingly pop up the
201 * process error dialog multiple times. See bug 345118 and bug 426163.
202 *
203 * We follow TerminateProcess() with a call to MOZ_NoReturn() so that the
204 * compiler doesn't hassle us to provide a return statement after a
205 * MOZ_REALLY_CRASH() call.
206 *
207 * (Technically these are Windows requirements, not MSVC requirements. But
208 * practically you need MSVC for debugging, and we only ship builds created
209 * by MSVC, so doing it this way reduces complexity.)
210 */
211
MOZ_NoReturn()212 __declspec(noreturn) __inline void MOZ_NoReturn() {}
213
214 # ifdef __cplusplus
215 # define MOZ_REALLY_CRASH() \
216 do { \
217 ::__debugbreak(); \
218 *((volatile int*) NULL) = __LINE__; \
219 ::TerminateProcess(::GetCurrentProcess(), 3); \
220 ::MOZ_NoReturn(); \
221 } while (0)
222 # else
223 # define MOZ_REALLY_CRASH() \
224 do { \
225 __debugbreak(); \
226 *((volatile int*) NULL) = __LINE__; \
227 TerminateProcess(GetCurrentProcess(), 3); \
228 MOZ_NoReturn(); \
229 } while (0)
230 # endif
231 #else
232 # ifdef __cplusplus
233 # define MOZ_REALLY_CRASH() \
234 do { \
235 *((volatile int*) NULL) = __LINE__; \
236 ::abort(); \
237 } while (0)
238 # else
239 # define MOZ_REALLY_CRASH() \
240 do { \
241 *((volatile int*) NULL) = __LINE__; \
242 abort(); \
243 } while (0)
244 # endif
245 #endif
246
247 /*
248 * MOZ_CRASH([explanation-string]) crashes the program, plain and simple, in a
249 * Breakpad-compatible way, in both debug and release builds.
250 *
251 * MOZ_CRASH is a good solution for "handling" failure cases when you're
252 * unwilling or unable to handle them more cleanly -- for OOM, for likely memory
253 * corruption, and so on. It's also a good solution if you need safe behavior
254 * in release builds as well as debug builds. But if the failure is one that
255 * should be debugged and fixed, MOZ_ASSERT is generally preferable.
256 *
257 * The optional explanation-string, if provided, must be a string literal
258 * explaining why we're crashing. This argument is intended for use with
259 * MOZ_CRASH() calls whose rationale is non-obvious; don't use it if it's
260 * obvious why we're crashing.
261 *
262 * If we're a DEBUG build and we crash at a MOZ_CRASH which provides an
263 * explanation-string, we print the string to stderr. Otherwise, we don't
264 * print anything; this is because we want MOZ_CRASH to be 100% safe in release
265 * builds, and it's hard to print to stderr safely when memory might have been
266 * corrupted.
267 */
268 #ifndef DEBUG
269 # define MOZ_CRASH(...) \
270 do { \
271 MOZ_CRASH_ANNOTATE("MOZ_CRASH(" __VA_ARGS__ ")"); \
272 MOZ_REALLY_CRASH(); \
273 } while (0)
274 #else
275 # define MOZ_CRASH(...) \
276 do { \
277 MOZ_ReportCrash("" __VA_ARGS__, __FILE__, __LINE__); \
278 MOZ_CRASH_ANNOTATE("MOZ_CRASH(" __VA_ARGS__ ")"); \
279 MOZ_REALLY_CRASH(); \
280 } while (0)
281 #endif
282
283 #ifdef __cplusplus
284 } /* extern "C" */
285 #endif
286
287 /*
288 * MOZ_ASSERT(expr [, explanation-string]) asserts that |expr| must be truthy in
289 * debug builds. If it is, execution continues. Otherwise, an error message
290 * including the expression and the explanation-string (if provided) is printed,
291 * an attempt is made to invoke any existing debugger, and execution halts.
292 * MOZ_ASSERT is fatal: no recovery is possible. Do not assert a condition
293 * which can correctly be falsy.
294 *
295 * The optional explanation-string, if provided, must be a string literal
296 * explaining the assertion. It is intended for use with assertions whose
297 * correctness or rationale is non-obvious, and for assertions where the "real"
298 * condition being tested is best described prosaically. Don't provide an
299 * explanation if it's not actually helpful.
300 *
301 * // No explanation needed: pointer arguments often must not be NULL.
302 * MOZ_ASSERT(arg);
303 *
304 * // An explanation can be helpful to explain exactly how we know an
305 * // assertion is valid.
306 * MOZ_ASSERT(state == WAITING_FOR_RESPONSE,
307 * "given that <thingA> and <thingB>, we must have...");
308 *
309 * // Or it might disambiguate multiple identical (save for their location)
310 * // assertions of the same expression.
311 * MOZ_ASSERT(getSlot(PRIMITIVE_THIS_SLOT).isUndefined(),
312 * "we already set [[PrimitiveThis]] for this Boolean object");
313 * MOZ_ASSERT(getSlot(PRIMITIVE_THIS_SLOT).isUndefined(),
314 * "we already set [[PrimitiveThis]] for this String object");
315 *
316 * MOZ_ASSERT has no effect in non-debug builds. It is designed to catch bugs
317 * *only* during debugging, not "in the field". If you want the latter, use
318 * MOZ_RELEASE_ASSERT, which applies to non-debug builds as well.
319 *
320 * MOZ_DIAGNOSTIC_ASSERT works like MOZ_RELEASE_ASSERT in Nightly/Aurora and
321 * MOZ_ASSERT in Beta/Release - use this when a condition is potentially rare
322 * enough to require real user testing to hit, but is not security-sensitive.
323 * This can cause user pain, so use it sparingly. If a MOZ_DIAGNOSTIC_ASSERT
324 * is firing, it should promptly be converted to a MOZ_ASSERT while the failure
325 * is being investigated, rather than letting users suffer.
326 */
327
328 /*
329 * Implement MOZ_VALIDATE_ASSERT_CONDITION_TYPE, which is used to guard against
330 * accidentally passing something unintended in lieu of an assertion condition.
331 */
332
333 #ifdef __cplusplus
334 # include "mozilla/TypeTraits.h"
335 namespace mozilla {
336 namespace detail {
337
338 template<typename T>
339 struct AssertionConditionType
340 {
341 typedef typename RemoveReference<T>::Type ValueT;
342 static_assert(!IsArray<ValueT>::value,
343 "Expected boolean assertion condition, got an array or a "
344 "string!");
345 static_assert(!IsFunction<ValueT>::value,
346 "Expected boolean assertion condition, got a function! Did "
347 "you intend to call that function?");
348 static_assert(!IsFloatingPoint<ValueT>::value,
349 "It's often a bad idea to assert that a floating-point number "
350 "is nonzero, because such assertions tend to intermittently "
351 "fail. Shouldn't your code gracefully handle this case instead "
352 "of asserting? Anyway, if you really want to do that, write an "
353 "explicit boolean condition, like !!x or x!=0.");
354
355 static const bool isValid = true;
356 };
357
358 } // namespace detail
359 } // namespace mozilla
360 # define MOZ_VALIDATE_ASSERT_CONDITION_TYPE(x) \
361 static_assert(mozilla::detail::AssertionConditionType<decltype(x)>::isValid, \
362 "invalid assertion condition")
363 #else
364 # define MOZ_VALIDATE_ASSERT_CONDITION_TYPE(x)
365 #endif
366
367 /* First the single-argument form. */
368 #define MOZ_ASSERT_HELPER1(expr) \
369 do { \
370 MOZ_VALIDATE_ASSERT_CONDITION_TYPE(expr); \
371 if (MOZ_UNLIKELY(!(expr))) { \
372 MOZ_ReportAssertionFailure(#expr, __FILE__, __LINE__); \
373 MOZ_CRASH_ANNOTATE("MOZ_RELEASE_ASSERT(" #expr ")"); \
374 MOZ_REALLY_CRASH(); \
375 } \
376 } while (0)
377 /* Now the two-argument form. */
378 #define MOZ_ASSERT_HELPER2(expr, explain) \
379 do { \
380 MOZ_VALIDATE_ASSERT_CONDITION_TYPE(expr); \
381 if (MOZ_UNLIKELY(!(expr))) { \
382 MOZ_ReportAssertionFailure(#expr " (" explain ")", __FILE__, __LINE__); \
383 MOZ_CRASH_ANNOTATE("MOZ_RELEASE_ASSERT(" #expr ") (" explain ")"); \
384 MOZ_REALLY_CRASH(); \
385 } \
386 } while (0)
387
388 #define MOZ_RELEASE_ASSERT_GLUE(a, b) a b
389 #define MOZ_RELEASE_ASSERT(...) \
390 MOZ_RELEASE_ASSERT_GLUE( \
391 MOZ_PASTE_PREFIX_AND_ARG_COUNT(MOZ_ASSERT_HELPER, __VA_ARGS__), \
392 (__VA_ARGS__))
393
394 #ifdef DEBUG
395 # define MOZ_ASSERT(...) MOZ_RELEASE_ASSERT(__VA_ARGS__)
396 #else
397 # define MOZ_ASSERT(...) do { } while (0)
398 #endif /* DEBUG */
399
400 #ifdef RELEASE_BUILD
401 # define MOZ_DIAGNOSTIC_ASSERT MOZ_ASSERT
402 #else
403 # define MOZ_DIAGNOSTIC_ASSERT MOZ_RELEASE_ASSERT
404 #endif
405
406 /*
407 * MOZ_ASSERT_IF(cond1, cond2) is equivalent to MOZ_ASSERT(cond2) if cond1 is
408 * true.
409 *
410 * MOZ_ASSERT_IF(isPrime(num), num == 2 || isOdd(num));
411 *
412 * As with MOZ_ASSERT, MOZ_ASSERT_IF has effect only in debug builds. It is
413 * designed to catch bugs during debugging, not "in the field".
414 */
415 #ifdef DEBUG
416 # define MOZ_ASSERT_IF(cond, expr) \
417 do { \
418 if (cond) { \
419 MOZ_ASSERT(expr); \
420 } \
421 } while (0)
422 #else
423 # define MOZ_ASSERT_IF(cond, expr) do { } while (0)
424 #endif
425
426 /*
427 * MOZ_ASSUME_UNREACHABLE_MARKER() expands to an expression which states that
428 * it is undefined behavior for execution to reach this point. No guarantees
429 * are made about what will happen if this is reached at runtime. Most code
430 * should use MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE because it has extra
431 * asserts.
432 */
433 #if defined(__clang__) || defined(__GNUC__)
434 # define MOZ_ASSUME_UNREACHABLE_MARKER() __builtin_unreachable()
435 #elif defined(_MSC_VER)
436 # define MOZ_ASSUME_UNREACHABLE_MARKER() __assume(0)
437 #else
438 # ifdef __cplusplus
439 # define MOZ_ASSUME_UNREACHABLE_MARKER() ::abort()
440 # else
441 # define MOZ_ASSUME_UNREACHABLE_MARKER() abort()
442 # endif
443 #endif
444
445 /*
446 * MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE([reason]) tells the compiler that it
447 * can assume that the macro call cannot be reached during execution. This lets
448 * the compiler generate better-optimized code under some circumstances, at the
449 * expense of the program's behavior being undefined if control reaches the
450 * MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE.
451 *
452 * In Gecko, you probably should not use this macro outside of performance- or
453 * size-critical code, because it's unsafe. If you don't care about code size
454 * or performance, you should probably use MOZ_ASSERT or MOZ_CRASH.
455 *
456 * SpiderMonkey is a different beast, and there it's acceptable to use
457 * MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE more widely.
458 *
459 * Note that MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE is noreturn, so it's valid
460 * not to return a value following a MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE
461 * call.
462 *
463 * Example usage:
464 *
465 * enum ValueType {
466 * VALUE_STRING,
467 * VALUE_INT,
468 * VALUE_FLOAT
469 * };
470 *
471 * int ptrToInt(ValueType type, void* value) {
472 * {
473 * // We know for sure that type is either INT or FLOAT, and we want this
474 * // code to run as quickly as possible.
475 * switch (type) {
476 * case VALUE_INT:
477 * return *(int*) value;
478 * case VALUE_FLOAT:
479 * return (int) *(float*) value;
480 * default:
481 * MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE("Unexpected ValueType");
482 * }
483 * }
484 */
485
486 /*
487 * Unconditional assert in debug builds for (assumed) unreachable code paths
488 * that have a safe return without crashing in release builds.
489 */
490 #define MOZ_ASSERT_UNREACHABLE(reason) \
491 MOZ_ASSERT(false, "MOZ_ASSERT_UNREACHABLE: " reason)
492
493 #define MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE(reason) \
494 do { \
495 MOZ_ASSERT_UNREACHABLE(reason); \
496 MOZ_ASSUME_UNREACHABLE_MARKER(); \
497 } while (0)
498
499 /*
500 * MOZ_ALWAYS_TRUE(expr) and MOZ_ALWAYS_FALSE(expr) always evaluate the provided
501 * expression, in debug builds and in release builds both. Then, in debug
502 * builds only, the value of the expression is asserted either true or false
503 * using MOZ_ASSERT.
504 */
505 #ifdef DEBUG
506 # define MOZ_ALWAYS_TRUE(expr) MOZ_ASSERT((expr))
507 # define MOZ_ALWAYS_FALSE(expr) MOZ_ASSERT(!(expr))
508 #else
509 # define MOZ_ALWAYS_TRUE(expr) \
510 do { \
511 if ( ( expr ) ) { \
512 /* Silence MOZ_WARN_UNUSED_RESULT. */ \
513 } \
514 } while (0)
515 # define MOZ_ALWAYS_FALSE(expr) \
516 do { \
517 if ( ( expr ) ) { \
518 /* Silence MOZ_WARN_UNUSED_RESULT. */ \
519 } \
520 } while (0)
521 #endif
522
523 #undef MOZ_DUMP_ASSERTION_STACK
524 #undef MOZ_CRASH_CRASHREPORT
525
526 #endif /* mozilla_Assertions_h */
527