mfbt/Attributes.h

   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 various class and method modifier attributes. */
   8
   9 #ifndef mozilla_Attributes_h
  10 #define mozilla_Attributes_h
  11
  12 #include "mozilla/Compiler.h"
  13
  14 /*
  15  * MOZ_ALWAYS_INLINE is a macro which expands to tell the compiler that the
  16  * method decorated with it must be inlined, even if the compiler thinks
  17  * otherwise.  This is only a (much) stronger version of the inline hint:
  18  * compilers are not guaranteed to respect it (although they're much more likely
  19  * to do so).
  20  *
  21  * The MOZ_ALWAYS_INLINE_EVEN_DEBUG macro is yet stronger. It tells the
  22  * compiler to inline even in DEBUG builds. It should be used very rarely.
  23  */
  24 #if defined(_MSC_VER)
  25 #  define MOZ_ALWAYS_INLINE_EVEN_DEBUG __forceinline
  26 #elif defined(__GNUC__)
  27 #  define MOZ_ALWAYS_INLINE_EVEN_DEBUG __attribute__((always_inline)) inline
  28 #else
  29 #  define MOZ_ALWAYS_INLINE_EVEN_DEBUG inline
  30 #endif
  31
  32 #if !defined(DEBUG)
  33 #  define MOZ_ALWAYS_INLINE MOZ_ALWAYS_INLINE_EVEN_DEBUG
  34 #elif defined(_MSC_VER) && !defined(__cplusplus)
  35 #  define MOZ_ALWAYS_INLINE __inline
  36 #else
  37 #  define MOZ_ALWAYS_INLINE inline
  38 #endif
  39
  40 #if defined(_MSC_VER)
  41 /*
  42  * g++ requires -std=c++0x or -std=gnu++0x to support C++11 functionality
  43  * without warnings (functionality used by the macros below).  These modes are
  44  * detectable by checking whether __GXX_EXPERIMENTAL_CXX0X__ is defined or, more
  45  * standardly, by checking whether __cplusplus has a C++11 or greater value.
  46  * Current versions of g++ do not correctly set __cplusplus, so we check both
  47  * for forward compatibility.
  48  */
  49 #  define MOZ_HAVE_NEVER_INLINE __declspec(noinline)
  50 #  define MOZ_HAVE_NORETURN __declspec(noreturn)
  51 #elif defined(__clang__)
  52 /*
  53  * Per Clang documentation, "Note that marketing version numbers should not
  54  * be used to check for language features, as different vendors use different
  55  * numbering schemes. Instead, use the feature checking macros."
  56  */
  57 #  ifndef __has_extension
  58 #    define __has_extension \
  59       __has_feature /* compatibility, for older versions of clang */
  60 #  endif
  61 #  if __has_attribute(noinline)
  62 #    define MOZ_HAVE_NEVER_INLINE __attribute__((noinline))
  63 #  endif
  64 #  if __has_attribute(noreturn)
  65 #    define MOZ_HAVE_NORETURN __attribute__((noreturn))
  66 #  endif
  67 #elif defined(__GNUC__)
  68 #  define MOZ_HAVE_NEVER_INLINE __attribute__((noinline))
  69 #  define MOZ_HAVE_NORETURN __attribute__((noreturn))
  70 #  define MOZ_HAVE_NORETURN_PTR __attribute__((noreturn))
  71 #endif
  72
  73 /*
  74  * When built with clang analyzer (a.k.a scan-build), define MOZ_HAVE_NORETURN
  75  * to mark some false positives
  76  */
  77 #ifdef __clang_analyzer__
  78 #  if __has_extension(attribute_analyzer_noreturn)
  79 #    define MOZ_HAVE_ANALYZER_NORETURN __attribute__((analyzer_noreturn))
  80 #  endif
  81 #endif
  82
  83 /*
  84  * MOZ_NEVER_INLINE is a macro which expands to tell the compiler that the
  85  * method decorated with it must never be inlined, even if the compiler would
  86  * otherwise choose to inline the method.  Compilers aren't absolutely
  87  * guaranteed to support this, but most do.
  88  */
  89 #if defined(MOZ_HAVE_NEVER_INLINE)
  90 #  define MOZ_NEVER_INLINE MOZ_HAVE_NEVER_INLINE
  91 #else
  92 #  define MOZ_NEVER_INLINE /* no support */
  93 #endif
  94
  95 /*
  96  * MOZ_NEVER_INLINE_DEBUG is a macro which expands to MOZ_NEVER_INLINE
  97  * in debug builds, and nothing in opt builds.
  98  */
  99 #if defined(DEBUG)
 100 #  define MOZ_NEVER_INLINE_DEBUG MOZ_NEVER_INLINE
 101 #else
 102 #  define MOZ_NEVER_INLINE_DEBUG /* don't inline in opt builds */
 103 #endif
 104 /*
 105  * MOZ_NORETURN, specified at the start of a function declaration, indicates
 106  * that the given function does not return.  (The function definition does not
 107  * need to be annotated.)
 108  *
 109  *   MOZ_NORETURN void abort(const char* msg);
 110  *
 111  * This modifier permits the compiler to optimize code assuming a call to such a
 112  * function will never return.  It also enables the compiler to avoid spurious
 113  * warnings about not initializing variables, or about any other seemingly-dodgy
 114  * operations performed after the function returns.
 115  *
 116  * There are two variants. The GCC version of NORETURN may be applied to a
 117  * function pointer, while for MSVC it may not.
 118  *
 119  * This modifier does not affect the corresponding function's linking behavior.
 120  */
 121 #if defined(MOZ_HAVE_NORETURN)
 122 #  define MOZ_NORETURN MOZ_HAVE_NORETURN
 123 #else
 124 #  define MOZ_NORETURN /* no support */
 125 #endif
 126 #if defined(MOZ_HAVE_NORETURN_PTR)
 127 #  define MOZ_NORETURN_PTR MOZ_HAVE_NORETURN_PTR
 128 #else
 129 #  define MOZ_NORETURN_PTR /* no support */
 130 #endif
 131
 132 /**
 133  * MOZ_COLD tells the compiler that a function is "cold", meaning infrequently
 134  * executed. This may lead it to optimize for size more aggressively than speed,
 135  * or to allocate the body of the function in a distant part of the text segment
 136  * to help keep it from taking up unnecessary icache when it isn't in use.
 137  *
 138  * Place this attribute at the very beginning of a function definition. For
 139  * example, write
 140  *
 141  *   MOZ_COLD int foo();
 142  *
 143  * or
 144  *
 145  *   MOZ_COLD int foo() { return 42; }
 146  */
 147 #if defined(__GNUC__) || defined(__clang__)
 148 #  define MOZ_COLD __attribute__((cold))
 149 #else
 150 #  define MOZ_COLD
 151 #endif
 152
 153 /**
 154  * MOZ_NONNULL tells the compiler that some of the arguments to a function are
 155  * known to be non-null. The arguments are a list of 1-based argument indexes
 156  * identifying arguments which are known to be non-null.
 157  *
 158  * Place this attribute at the very beginning of a function definition. For
 159  * example, write
 160  *
 161  *   MOZ_NONNULL(1, 2) int foo(char *p, char *q);
 162  */
 163 #if defined(__GNUC__) || defined(__clang__)
 164 #  define MOZ_NONNULL(...) __attribute__((nonnull(__VA_ARGS__)))
 165 #else
 166 #  define MOZ_NONNULL(...)
 167 #endif
 168
 169 /**
 170  * MOZ_NONNULL_RETURN tells the compiler that the function's return value is
 171  * guaranteed to be a non-null pointer, which may enable the compiler to
 172  * optimize better at call sites.
 173  *
 174  * Place this attribute at the end of a function declaration. For example,
 175  *
 176  *   char* foo(char *p, char *q) MOZ_NONNULL_RETURN;
 177  */
 178 #if defined(__GNUC__) || defined(__clang__)
 179 #  define MOZ_NONNULL_RETURN __attribute__((returns_nonnull))
 180 #else
 181 #  define MOZ_NONNULL_RETURN
 182 #endif
 183
 184 /*
 185  * MOZ_PRETEND_NORETURN_FOR_STATIC_ANALYSIS, specified at the end of a function
 186  * declaration, indicates that for the purposes of static analysis, this
 187  * function does not return.  (The function definition does not need to be
 188  * annotated.)
 189  *
 190  * MOZ_ReportCrash(const char* s, const char* file, int ln)
 191  *   MOZ_PRETEND_NORETURN_FOR_STATIC_ANALYSIS
 192  *
 193  * Some static analyzers, like scan-build from clang, can use this information
 194  * to eliminate false positives.  From the upstream documentation of scan-build:
 195  * "This attribute is useful for annotating assertion handlers that actually
 196  * can return, but for the purpose of using the analyzer we want to pretend
 197  * that such functions do not return."
 198  *
 199  */
 200 #if defined(MOZ_HAVE_ANALYZER_NORETURN)
 201 #  define MOZ_PRETEND_NORETURN_FOR_STATIC_ANALYSIS MOZ_HAVE_ANALYZER_NORETURN
 202 #else
 203 #  define MOZ_PRETEND_NORETURN_FOR_STATIC_ANALYSIS /* no support */
 204 #endif
 205
 206 /*
 207  * MOZ_ASAN_BLACKLIST is a macro to tell AddressSanitizer (a compile-time
 208  * instrumentation shipped with Clang and GCC) to not instrument the annotated
 209  * function. Furthermore, it will prevent the compiler from inlining the
 210  * function because inlining currently breaks the blacklisting mechanism of
 211  * AddressSanitizer.
 212  */
 213 #if defined(__has_feature)
 214 #  if __has_feature(address_sanitizer)
 215 #    define MOZ_HAVE_ASAN_BLACKLIST
 216 #  endif
 217 #elif defined(__GNUC__)
 218 #  if defined(__SANITIZE_ADDRESS__)
 219 #    define MOZ_HAVE_ASAN_BLACKLIST
 220 #  endif
 221 #endif
 222
 223 #if defined(MOZ_HAVE_ASAN_BLACKLIST)
 224 #  define MOZ_ASAN_BLACKLIST \
 225     MOZ_NEVER_INLINE __attribute__((no_sanitize_address))
 226 #else
 227 #  define MOZ_ASAN_BLACKLIST /* nothing */
 228 #endif
 229
 230 /*
 231  * MOZ_TSAN_BLACKLIST is a macro to tell ThreadSanitizer (a compile-time
 232  * instrumentation shipped with Clang) to not instrument the annotated function.
 233  * Furthermore, it will prevent the compiler from inlining the function because
 234  * inlining currently breaks the blacklisting mechanism of ThreadSanitizer.
 235  */
 236 #if defined(__has_feature)
 237 #  if __has_feature(thread_sanitizer)
 238 #    define MOZ_TSAN_BLACKLIST \
 239       MOZ_NEVER_INLINE __attribute__((no_sanitize_thread))
 240 #  else
 241 #    define MOZ_TSAN_BLACKLIST /* nothing */
 242 #  endif
 243 #else
 244 #  define MOZ_TSAN_BLACKLIST /* nothing */
 245 #endif
 246
 247 #if defined(__has_attribute)
 248 #  if __has_attribute(no_sanitize)
 249 #    define MOZ_HAVE_NO_SANITIZE_ATTR
 250 #  endif
 251 #endif
 252
 253 #ifdef __clang__
 254 #  ifdef MOZ_HAVE_NO_SANITIZE_ATTR
 255 #    define MOZ_HAVE_UNSIGNED_OVERFLOW_SANITIZE_ATTR
 256 #    define MOZ_HAVE_SIGNED_OVERFLOW_SANITIZE_ATTR
 257 #  endif
 258 #endif
 259
 260 /*
 261  * MOZ_NO_SANITIZE_UNSIGNED_OVERFLOW disables *un*signed integer overflow
 262  * checking on the function it annotates, in builds configured to perform it.
 263  * (Currently this is only Clang using -fsanitize=unsigned-integer-overflow, or
 264  * via --enable-unsigned-overflow-sanitizer in Mozilla's build system.)  It has
 265  * no effect in other builds.
 266  *
 267  * Place this attribute at the very beginning of a function declaration.
 268  *
 269  * Unsigned integer overflow isn't *necessarily* a bug.  It's well-defined in
 270  * C/C++, and code may reasonably depend upon it.  For example,
 271  *
 272  *   MOZ_NO_SANITIZE_UNSIGNED_OVERFLOW inline bool
 273  *   IsDecimal(char aChar)
 274  *   {
 275  *     // For chars less than '0', unsigned integer underflow occurs, to a value
 276  *     // much greater than 10, so the overall test is false.
 277  *     // For chars greater than '0', no overflow occurs, and only '0' to '9'
 278  *     // pass the overall test.
 279  *     return static_cast<unsigned int>(aChar) - '0' < 10;
 280  *   }
 281  *
 282  * But even well-defined unsigned overflow often causes bugs when it occurs, so
 283  * it should be restricted to functions annotated with this attribute.
 284  *
 285  * The compiler instrumentation to detect unsigned integer overflow has costs
 286  * both at compile time and at runtime.  Functions that are repeatedly inlined
 287  * at compile time will also implicitly inline the necessary instrumentation,
 288  * increasing compile time.  Similarly, frequently-executed functions that
 289  * require large amounts of instrumentation will also notice significant runtime
 290  * slowdown to execute that instrumentation.  Use this attribute to eliminate
 291  * those costs -- but only after carefully verifying that no overflow can occur.
 292  */
 293 #ifdef MOZ_HAVE_UNSIGNED_OVERFLOW_SANITIZE_ATTR
 294 #  define MOZ_NO_SANITIZE_UNSIGNED_OVERFLOW \
 295     __attribute__((no_sanitize("unsigned-integer-overflow")))
 296 #else
 297 #  define MOZ_NO_SANITIZE_UNSIGNED_OVERFLOW /* nothing */
 298 #endif
 299
 300 /*
 301  * MOZ_NO_SANITIZE_SIGNED_OVERFLOW disables *signed* integer overflow checking
 302  * on the function it annotates, in builds configured to perform it.  (Currently
 303  * this is only Clang using -fsanitize=signed-integer-overflow, or via
 304  * --enable-signed-overflow-sanitizer in Mozilla's build system.  GCC support
 305  * will probably be added in the future.)  It has no effect in other builds.
 306  *
 307  * Place this attribute at the very beginning of a function declaration.
 308  *
 309  * Signed integer overflow is undefined behavior in C/C++: *anything* can happen
 310  * when it occurs.  *Maybe* wraparound behavior will occur, but maybe also the
 311  * compiler will assume no overflow happens and will adversely optimize the rest
 312  * of your code.  Code that contains signed integer overflow needs to be fixed.
 313  *
 314  * The compiler instrumentation to detect signed integer overflow has costs both
 315  * at compile time and at runtime.  Functions that are repeatedly inlined at
 316  * compile time will also implicitly inline the necessary instrumentation,
 317  * increasing compile time.  Similarly, frequently-executed functions that
 318  * require large amounts of instrumentation will also notice significant runtime
 319  * slowdown to execute that instrumentation.  Use this attribute to eliminate
 320  * those costs -- but only after carefully verifying that no overflow can occur.
 321  */
 322 #ifdef MOZ_HAVE_SIGNED_OVERFLOW_SANITIZE_ATTR
 323 #  define MOZ_NO_SANITIZE_SIGNED_OVERFLOW \
 324     __attribute__((no_sanitize("signed-integer-overflow")))
 325 #else
 326 #  define MOZ_NO_SANITIZE_SIGNED_OVERFLOW /* nothing */
 327 #endif
 328
 329 #undef MOZ_HAVE_NO_SANITIZE_ATTR
 330
 331 /**
 332  * MOZ_ALLOCATOR tells the compiler that the function it marks returns either a
 333  * "fresh", "pointer-free" block of memory, or nullptr. "Fresh" means that the
 334  * block is not pointed to by any other reachable pointer in the program.
 335  * "Pointer-free" means that the block contains no pointers to any valid object
 336  * in the program. It may be initialized with other (non-pointer) values.
 337  *
 338  * Placing this attribute on appropriate functions helps GCC analyze pointer
 339  * aliasing more accurately in their callers.
 340  *
 341  * GCC warns if a caller ignores the value returned by a function marked with
 342  * MOZ_ALLOCATOR: it is hard to imagine cases where dropping the value returned
 343  * by a function that meets the criteria above would be intentional.
 344  *
 345  * Place this attribute after the argument list and 'this' qualifiers of a
 346  * function definition. For example, write
 347  *
 348  *   void *my_allocator(size_t) MOZ_ALLOCATOR;
 349  *
 350  * or
 351  *
 352  *   void *my_allocator(size_t bytes) MOZ_ALLOCATOR { ... }
 353  */
 354 #if defined(__GNUC__) || defined(__clang__)
 355 #  define MOZ_ALLOCATOR __attribute__((malloc, warn_unused_result))
 356 #  define MOZ_INFALLIBLE_ALLOCATOR \
 357     __attribute__((malloc, warn_unused_result, returns_nonnull))
 358 #else
 359 #  define MOZ_ALLOCATOR
 360 #  define MOZ_INFALLIBLE_ALLOCATOR
 361 #endif
 362
 363 /**
 364  * MOZ_MAYBE_UNUSED suppresses compiler warnings about functions that are
 365  * never called (in this build configuration, at least).
 366  *
 367  * Place this attribute at the very beginning of a function declaration. For
 368  * example, write
 369  *
 370  *   MOZ_MAYBE_UNUSED int foo();
 371  *
 372  * or
 373  *
 374  *   MOZ_MAYBE_UNUSED int foo() { return 42; }
 375  */
 376 #if defined(__GNUC__) || defined(__clang__)
 377 #  define MOZ_MAYBE_UNUSED __attribute__((__unused__))
 378 #elif defined(_MSC_VER)
 379 #  define MOZ_MAYBE_UNUSED __pragma(warning(suppress : 4505))
 380 #else
 381 #  define MOZ_MAYBE_UNUSED
 382 #endif
 383
 384 #ifdef __cplusplus
 385
 386 /**
 387  * C++11 lets unions contain members that have non-trivial special member
 388  * functions (default/copy/move constructor, copy/move assignment operator,
 389  * destructor) if the user defines the corresponding functions on the union.
 390  * (Such user-defined functions must rely on external knowledge about which arm
 391  * is active to be safe.  Be extra-careful defining these functions!)
 392  *
 393  * MSVC unfortunately warns/errors for this bog-standard C++11 pattern.  Use
 394  * these macro-guards around such member functions to disable the warnings:
 395  *
 396  *   union U
 397  *   {
 398  *     std::string s;
 399  *     int x;
 400  *
 401  *     MOZ_PUSH_DISABLE_NONTRIVIAL_UNION_WARNINGS
 402  *
 403  *     // |U| must have a user-defined default constructor because |std::string|
 404  *     // has a non-trivial default constructor.
 405  *     U() ... { ... }
 406  *
 407  *     // |U| must have a user-defined destructor because |std::string| has a
 408  *     // non-trivial destructor.
 409  *     ~U() { ... }
 410  *
 411  *     MOZ_POP_DISABLE_NONTRIVIAL_UNION_WARNINGS
 412  *   };
 413  */
 414 #  if defined(_MSC_VER)
 415 #    define MOZ_PUSH_DISABLE_NONTRIVIAL_UNION_WARNINGS          \
 416       __pragma(warning(push)) __pragma(warning(disable : 4582)) \
 417           __pragma(warning(disable : 4583))
 418 #    define MOZ_POP_DISABLE_NONTRIVIAL_UNION_WARNINGS __pragma(warning(pop))
 419 #  else
 420 #    define MOZ_PUSH_DISABLE_NONTRIVIAL_UNION_WARNINGS /* nothing */
 421 #    define MOZ_POP_DISABLE_NONTRIVIAL_UNION_WARNINGS  /* nothing */
 422 #  endif
 423
 424 /*
 425  * The following macros are attributes that support the static analysis plugin
 426  * included with Mozilla, and will be implemented (when such support is enabled)
 427  * as C++11 attributes. Since such attributes are legal pretty much everywhere
 428  * and have subtly different semantics depending on their placement, the
 429  * following is a guide on where to place the attributes.
 430  *
 431  * Attributes that apply to a struct or class precede the name of the class:
 432  * (Note that this is different from the placement of final for classes!)
 433  *
 434  *   class MOZ_CLASS_ATTRIBUTE SomeClass {};
 435  *
 436  * Attributes that apply to functions follow the parentheses and const
 437  * qualifiers but precede final, override and the function body:
 438  *
 439  *   void DeclaredFunction() MOZ_FUNCTION_ATTRIBUTE;
 440  *   void SomeFunction() MOZ_FUNCTION_ATTRIBUTE {}
 441  *   void PureFunction() const MOZ_FUNCTION_ATTRIBUTE = 0;
 442  *   void OverriddenFunction() MOZ_FUNCTION_ATTIRBUTE override;
 443  *
 444  * Attributes that apply to variables or parameters follow the variable's name:
 445  *
 446  *   int variable MOZ_VARIABLE_ATTRIBUTE;
 447  *
 448  * Attributes that apply to types follow the type name:
 449  *
 450  *   typedef int MOZ_TYPE_ATTRIBUTE MagicInt;
 451  *   int MOZ_TYPE_ATTRIBUTE someVariable;
 452  *   int* MOZ_TYPE_ATTRIBUTE magicPtrInt;
 453  *   int MOZ_TYPE_ATTRIBUTE* ptrToMagicInt;
 454  *
 455  * Attributes that apply to statements precede the statement:
 456  *
 457  *   MOZ_IF_ATTRIBUTE if (x == 0)
 458  *   MOZ_DO_ATTRIBUTE do { } while (0);
 459  *
 460  * Attributes that apply to labels precede the label:
 461  *
 462  *   MOZ_LABEL_ATTRIBUTE target:
 463  *     goto target;
 464  *   MOZ_CASE_ATTRIBUTE case 5:
 465  *   MOZ_DEFAULT_ATTRIBUTE default:
 466  *
 467  * The static analyses that are performed by the plugin are as follows:
 468  *
 469  * MOZ_CAN_RUN_SCRIPT: Applies to functions which can run script. Callers of
 470  *   this function must also be marked as MOZ_CAN_RUN_SCRIPT, and all refcounted
 471  *   arguments must be strongly held in the caller. Note that MOZ_CAN_RUN_SCRIPT
 472  *   should only be applied to function declarations, not definitions. If you
 473  *   need to apply it to a definition (eg because both are generated by a macro)
 474  *   use MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION.
 475  *
 476  *   MOZ_CAN_RUN_SCRIPT can be applied to XPIDL-generated declarations by
 477  *   annotating the method or attribute as [can_run_script] in the .idl file.
 478  *
 479  * MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION: Same as MOZ_CAN_RUN_SCRIPT, but usable on
 480  *   a definition. If the declaration is in a header file, users of that header
 481  *   file may not see the annotation.
 482  * MOZ_CAN_RUN_SCRIPT_BOUNDARY: Applies to functions which need to call
 483  *   MOZ_CAN_RUN_SCRIPT functions, but should not themselves be considered
 484  *   MOZ_CAN_RUN_SCRIPT. This should generally be avoided but can be used in
 485  *   two cases:
 486  *     1) As a temporary measure to limit the scope of changes when adding
 487  *        MOZ_CAN_RUN_SCRIPT.  Such a use must be accompanied by a follow-up bug
 488  *        to replace the MOZ_CAN_RUN_SCRIPT_BOUNDARY with MOZ_CAN_RUN_SCRIPT and
 489  *        a comment linking to that bug.
 490  *     2) If we can reason that the MOZ_CAN_RUN_SCRIPT callees of the function
 491  *        do not in fact run script (for example, because their behavior depends
 492  *        on arguments and we pass the arguments that don't allow script
 493  *        execution).  Such a use must be accompanied by a comment that explains
 494  *        why it's OK to have the MOZ_CAN_RUN_SCRIPT_BOUNDARY, as well as
 495  *        comments in the callee pointing out that if its behavior changes the
 496  *        caller might need adjusting.  And perhaps also a followup bug to
 497  *        refactor things so the "script" and "no script" codepaths do not share
 498  *        a chokepoint.
 499  *   Importantly, any use MUST be accompanied by a comment explaining why it's
 500  *   there, and should ideally have an action plan for getting rid of the
 501  *   MOZ_CAN_RUN_SCRIPT_BOUNDARY annotation.
 502  * MOZ_MUST_OVERRIDE: Applies to all C++ member functions. All immediate
 503  *   subclasses must provide an exact override of this method; if a subclass
 504  *   does not override this method, the compiler will emit an error. This
 505  *   attribute is not limited to virtual methods, so if it is applied to a
 506  *   nonvirtual method and the subclass does not provide an equivalent
 507  *   definition, the compiler will emit an error.
 508  * MOZ_STATIC_CLASS: Applies to all classes. Any class with this annotation is
 509  *   expected to live in static memory, so it is a compile-time error to use
 510  *   it, or an array of such objects, as the type of a variable declaration, or
 511  *   as a temporary object, or as the type of a new expression (unless
 512  *   placement new is being used). If a member of another class uses this
 513  *   class, or if another class inherits from this class, then it is considered
 514  *   to be a static class as well, although this attribute need not be provided
 515  *   in such cases.
 516  * MOZ_STATIC_LOCAL_CLASS: Applies to all classes. Any class with this
 517  *   annotation is expected to be a static local variable, so it is
 518  *   a compile-time error to use it, or an array of such objects, or as a
 519  *   temporary object, or as the type of a new expression. If another class
 520  *   inherits from this class then it is considered to be a static local
 521  *   class as well, although this attribute need not be provided in such cases.
 522  *   It is also a compile-time error for any class with this annotation to have
 523  *   a non-trivial destructor.
 524  * MOZ_STACK_CLASS: Applies to all classes. Any class with this annotation is
 525  *   expected to live on the stack, so it is a compile-time error to use it, or
 526  *   an array of such objects, as a global or static variable, or as the type of
 527  *   a new expression (unless placement new is being used). If a member of
 528  *   another class uses this class, or if another class inherits from this
 529  *   class, then it is considered to be a stack class as well, although this
 530  *   attribute need not be provided in such cases.
 531  * MOZ_NONHEAP_CLASS: Applies to all classes. Any class with this annotation is
 532  *   expected to live on the stack or in static storage, so it is a compile-time
 533  *   error to use it, or an array of such objects, as the type of a new
 534  *   expression. If a member of another class uses this class, or if another
 535  *   class inherits from this class, then it is considered to be a non-heap
 536  *   class as well, although this attribute need not be provided in such cases.
 537  * MOZ_HEAP_CLASS: Applies to all classes. Any class with this annotation is
 538  *   expected to live on the heap, so it is a compile-time error to use it, or
 539  *   an array of such objects, as the type of a variable declaration, or as a
 540  *   temporary object. If a member of another class uses this class, or if
 541  *   another class inherits from this class, then it is considered to be a heap
 542  *   class as well, although this attribute need not be provided in such cases.
 543  * MOZ_NON_TEMPORARY_CLASS: Applies to all classes. Any class with this
 544  *   annotation is expected not to live in a temporary. If a member of another
 545  *   class uses this class or if another class inherits from this class, then it
 546  *   is considered to be a non-temporary class as well, although this attribute
 547  *   need not be provided in such cases.
 548  * MOZ_TEMPORARY_CLASS: Applies to all classes. Any class with this annotation
 549  *   is expected to only live in a temporary. If another class inherits from
 550  *   this class, then it is considered to be a non-temporary class as well,
 551  *   although this attribute need not be provided in such cases.
 552  * MOZ_RAII: Applies to all classes. Any class with this annotation is assumed
 553  *   to be a RAII guard, which is expected to live on the stack in an automatic
 554  *   allocation. It is prohibited from being allocated in a temporary, static
 555  *   storage, or on the heap. This is a combination of MOZ_STACK_CLASS and
 556  *   MOZ_NON_TEMPORARY_CLASS.
 557  * MOZ_ONLY_USED_TO_AVOID_STATIC_CONSTRUCTORS: Applies to all classes that are
 558  *   intended to prevent introducing static initializers.  This attribute
 559  *   currently makes it a compile-time error to instantiate these classes
 560  *   anywhere other than at the global scope, or as a static member of a class.
 561  *   In non-debug mode, it also prohibits non-trivial constructors and
 562  *   destructors.
 563  * MOZ_TRIVIAL_CTOR_DTOR: Applies to all classes that must have both a trivial
 564  *   or constexpr constructor and a trivial destructor. Setting this attribute
 565  *   on a class makes it a compile-time error for that class to get a
 566  *   non-trivial constructor or destructor for any reason.
 567  * MOZ_ALLOW_TEMPORARY: Applies to constructors. This indicates that using the
 568  *   constructor is allowed in temporary expressions, if it would have otherwise
 569  *   been forbidden by the type being a MOZ_NON_TEMPORARY_CLASS. Useful for
 570  *   constructors like Maybe(Nothing).
 571  * MOZ_HEAP_ALLOCATOR: Applies to any function. This indicates that the return
 572  *   value is allocated on the heap, and will as a result check such allocations
 573  *   during MOZ_STACK_CLASS and MOZ_NONHEAP_CLASS annotation checking.
 574  * MOZ_IMPLICIT: Applies to constructors. Implicit conversion constructors
 575  *   are disallowed by default unless they are marked as MOZ_IMPLICIT. This
 576  *   attribute must be used for constructors which intend to provide implicit
 577  *   conversions.
 578  * MOZ_IS_REFPTR: Applies to class declarations of ref pointer to mark them as
 579  *   such for use with static-analysis.
 580  *   A ref pointer is an object wrapping a pointer and automatically taking care
 581  *   of its refcounting upon construction/destruction/transfer of ownership.
 582  *   This annotation implies MOZ_IS_SMARTPTR_TO_REFCOUNTED.
 583  * MOZ_IS_SMARTPTR_TO_REFCOUNTED: Applies to class declarations of smart
 584  *   pointers to ref counted classes to mark them as such for use with
 585  *   static-analysis.
 586  * MOZ_NO_ARITHMETIC_EXPR_IN_ARGUMENT: Applies to functions. Makes it a compile
 587  *   time error to pass arithmetic expressions on variables to the function.
 588  * MOZ_OWNING_REF: Applies to declarations of pointers to reference counted
 589  *   types.  This attribute tells the compiler that the raw pointer is a strong
 590  *   reference, where ownership through methods such as AddRef and Release is
 591  *   managed manually.  This can make the compiler ignore these pointers when
 592  *   validating the usage of pointers otherwise.
 593  *
 594  *   Example uses include owned pointers inside of unions, and pointers stored
 595  *   in POD types where a using a smart pointer class would make the object
 596  *   non-POD.
 597  * MOZ_NON_OWNING_REF: Applies to declarations of pointers to reference counted
 598  *   types.  This attribute tells the compiler that the raw pointer is a weak
 599  *   reference, which is ensured to be valid by a guarantee that the reference
 600  *   will be nulled before the pointer becomes invalid.  This can make the
 601  *   compiler ignore these pointers when validating the usage of pointers
 602  *   otherwise.
 603  *
 604  *   Examples include an mOwner pointer, which is nulled by the owning class's
 605  *   destructor, and is null-checked before dereferencing.
 606  * MOZ_UNSAFE_REF: Applies to declarations of pointers to reference counted
 607  *   types.  Occasionally there are non-owning references which are valid, but
 608  *   do not take the form of a MOZ_NON_OWNING_REF.  Their safety may be
 609  *   dependent on the behaviour of API consumers.  The string argument passed
 610  *   to this macro documents the safety conditions.  This can make the compiler
 611  *   ignore these pointers when validating the usage of pointers elsewhere.
 612  *
 613  *   Examples include an nsAtom* member which is known at compile time to point
 614  *   to a static atom which is valid throughout the lifetime of the program, or
 615  *   an API which stores a pointer, but doesn't take ownership over it, instead
 616  *   requiring the API consumer to correctly null the value before it becomes
 617  *   invalid.
 618  *
 619  *   Use of this annotation is discouraged when a strong reference or one of
 620  *   the above two annotations can be used instead.
 621  * MOZ_NO_ADDREF_RELEASE_ON_RETURN: Applies to function declarations.  Makes it
 622  *   a compile time error to call AddRef or Release on the return value of a
 623  *   function.  This is intended to be used with operator->() of our smart
 624  *   pointer classes to ensure that the refcount of an object wrapped in a
 625  *   smart pointer is not manipulated directly.
 626  * MOZ_NEEDS_NO_VTABLE_TYPE: Applies to template class declarations.  Makes it
 627  *   a compile time error to instantiate this template with a type parameter
 628  *   which has a VTable.
 629  * MOZ_NON_MEMMOVABLE: Applies to class declarations for types that are not safe
 630  *   to be moved in memory using memmove().
 631  * MOZ_NEEDS_MEMMOVABLE_TYPE: Applies to template class declarations where the
 632  *   template arguments are required to be safe to move in memory using
 633  *   memmove().  Passing MOZ_NON_MEMMOVABLE types to these templates is a
 634  *   compile time error.
 635  * MOZ_NEEDS_MEMMOVABLE_MEMBERS: Applies to class declarations where each member
 636  *   must be safe to move in memory using memmove().  MOZ_NON_MEMMOVABLE types
 637  *   used in members of these classes are compile time errors.
 638  * MOZ_NO_DANGLING_ON_TEMPORARIES: Applies to method declarations which return
 639  *   a pointer that is freed when the destructor of the class is called. This
 640  *   prevents these methods from being called on temporaries of the class,
 641  *   reducing risks of use-after-free.
 642  *   This attribute cannot be applied to && methods.
 643  *   In some cases, adding a deleted &&-qualified overload is too restrictive as
 644  *   this method should still be callable as a non-escaping argument to another
 645  *   function. This annotation can be used in those cases.
 646  * MOZ_INHERIT_TYPE_ANNOTATIONS_FROM_TEMPLATE_ARGS: Applies to template class
 647  *   declarations where an instance of the template should be considered, for
 648  *   static analysis purposes, to inherit any type annotations (such as
 649  *   MOZ_STACK_CLASS) from its template arguments.
 650  * MOZ_INIT_OUTSIDE_CTOR: Applies to class member declarations. Occasionally
 651  *   there are class members that are not initialized in the constructor,
 652  *   but logic elsewhere in the class ensures they are initialized prior to use.
 653  *   Using this attribute on a member disables the check that this member must
 654  *   be initialized in constructors via list-initialization, in the constructor
 655  *   body, or via functions called from the constructor body.
 656  * MOZ_IS_CLASS_INIT: Applies to class method declarations. Occasionally the
 657  *   constructor doesn't initialize all of the member variables and another
 658  *   function is used to initialize the rest. This marker is used to make the
 659  *   static analysis tool aware that the marked function is part of the
 660  *   initialization process and to include the marked function in the scan
 661  *   mechanism that determines which member variables still remain
 662  *   uninitialized.
 663  * MOZ_NON_PARAM: Applies to types. Makes it compile time error to use the type
 664  *   in parameter without pointer or reference.
 665  * MOZ_NON_AUTOABLE: Applies to class declarations. Makes it a compile time
 666  *   error to use `auto` in place of this type in variable declarations.  This
 667  *   is intended to be used with types which are intended to be implicitly
 668  *   constructed into other other types before being assigned to variables.
 669  * MOZ_REQUIRED_BASE_METHOD: Applies to virtual class method declarations.
 670  *   Sometimes derived classes override methods that need to be called by their
 671  *   overridden counterparts. This marker indicates that the marked method must
 672  *   be called by the method that it overrides.
 673  * MOZ_MUST_RETURN_FROM_CALLER_IF_THIS_IS_ARG: Applies to method declarations.
 674  *   Callers of the annotated method must return from that function within the
 675  *   calling block using an explicit `return` statement if the "this" value for
 676  *   the call is a parameter of the caller.  Only calls to Constructors,
 677  *   references to local and member variables, and calls to functions or
 678  *   methods marked as MOZ_MAY_CALL_AFTER_MUST_RETURN may be made after the
 679  *   MOZ_MUST_RETURN_FROM_CALLER_IF_THIS_IS_ARG call.
 680  * MOZ_MAY_CALL_AFTER_MUST_RETURN: Applies to function or method declarations.
 681  *   Calls to these methods may be made in functions after calls a
 682  *   MOZ_MUST_RETURN_FROM_CALLER_IF_THIS_IS_ARG method.
 683  * MOZ_LIFETIME_BOUND: Applies to method declarations.
 684  *   The result of calling these functions on temporaries may not be returned as
 685  *   a reference or bound to a reference variable.
 686  * MOZ_UNANNOTATED/MOZ_ANNOTATED: Applies to Mutexes/Monitors and variations on
 687  *   them. MOZ_UNANNOTATED indicates that the Mutex/Monitor/etc hasn't been
 688  *   examined and annotated using macros from mfbt/ThreadSafety --
 689  *   MOZ_GUARDED_BY()/REQUIRES()/etc. MOZ_ANNOTATED is used in rare cases to
 690  *   indicate that is has been looked at, but it did not need any
 691  *   MOZ_GUARDED_BY()/REQUIRES()/etc (and thus static analysis knows it can
 692  * ignore this Mutex/Monitor/etc)
 693  */
 694
 695 // gcc emits a nuisance warning -Wignored-attributes because attributes do not
 696 // affect mangled names, and therefore template arguments do not propagate
 697 // their attributes. It is rare that this would affect anything in practice,
 698 // and most compilers are silent about it. Similarly, -Wattributes complains
 699 // about attributes being ignored during template instantiation.
 700 //
 701 // Be conservative and only suppress the warning when running in a
 702 // configuration where it would be emitted, namely when compiling with the
 703 // XGILL_PLUGIN for the rooting hazard analysis (which runs under gcc.) If we
 704 // end up wanting these attributes in general GCC builds, change this to
 705 // something like
 706 //
 707 //     #if defined(__GNUC__) && ! defined(__clang__)
 708 //
 709 #  ifdef XGILL_PLUGIN
 710 #    pragma GCC diagnostic ignored "-Wignored-attributes"
 711 #    pragma GCC diagnostic ignored "-Wattributes"
 712 #  endif
 713
 714 #  if defined(MOZ_CLANG_PLUGIN) || defined(XGILL_PLUGIN)
 715 #    define MOZ_CAN_RUN_SCRIPT __attribute__((annotate("moz_can_run_script")))
 716 #    define MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION         \
 717       __attribute__((annotate("moz_can_run_script"))) \
 718       __attribute__((annotate("moz_can_run_script_for_definition")))
 719 #    define MOZ_CAN_RUN_SCRIPT_BOUNDARY \
 720       __attribute__((annotate("moz_can_run_script_boundary")))
 721 #    define MOZ_MUST_OVERRIDE __attribute__((annotate("moz_must_override")))
 722 #    define MOZ_STATIC_CLASS __attribute__((annotate("moz_global_class")))
 723 #    define MOZ_STATIC_LOCAL_CLASS                        \
 724       __attribute__((annotate("moz_static_local_class"))) \
 725       __attribute__((annotate("moz_trivial_dtor")))
 726 #    define MOZ_STACK_CLASS __attribute__((annotate("moz_stack_class")))
 727 #    define MOZ_NONHEAP_CLASS __attribute__((annotate("moz_nonheap_class")))
 728 #    define MOZ_HEAP_CLASS __attribute__((annotate("moz_heap_class")))
 729 #    define MOZ_NON_TEMPORARY_CLASS \
 730       __attribute__((annotate("moz_non_temporary_class")))
 731 #    define MOZ_TEMPORARY_CLASS __attribute__((annotate("moz_temporary_class")))
 732 #    define MOZ_TRIVIAL_CTOR_DTOR \
 733       __attribute__((annotate("moz_trivial_ctor_dtor")))
 734 #    define MOZ_ALLOW_TEMPORARY __attribute__((annotate("moz_allow_temporary")))
 735 #    ifdef DEBUG
 736 /* in debug builds, these classes do have non-trivial constructors. */
 737 #      define MOZ_ONLY_USED_TO_AVOID_STATIC_CONSTRUCTORS \
 738         __attribute__((annotate("moz_global_class")))
 739 #    else
 740 #      define MOZ_ONLY_USED_TO_AVOID_STATIC_CONSTRUCTORS \
 741         __attribute__((annotate("moz_global_class"))) MOZ_TRIVIAL_CTOR_DTOR
 742 #    endif
 743 #    define MOZ_IMPLICIT __attribute__((annotate("moz_implicit")))
 744 #    define MOZ_IS_SMARTPTR_TO_REFCOUNTED \
 745       __attribute__((annotate("moz_is_smartptr_to_refcounted")))
 746 #    define MOZ_IS_REFPTR MOZ_IS_SMARTPTR_TO_REFCOUNTED
 747 #    define MOZ_NO_ARITHMETIC_EXPR_IN_ARGUMENT \
 748       __attribute__((annotate("moz_no_arith_expr_in_arg")))
 749 #    define MOZ_OWNING_REF __attribute__((annotate("moz_owning_ref")))
 750 #    define MOZ_NON_OWNING_REF __attribute__((annotate("moz_non_owning_ref")))
 751 #    define MOZ_UNSAFE_REF(reason) __attribute__((annotate("moz_unsafe_ref")))
 752 #    define MOZ_NO_ADDREF_RELEASE_ON_RETURN \
 753       __attribute__((annotate("moz_no_addref_release_on_return")))
 754 #    define MOZ_NEEDS_NO_VTABLE_TYPE \
 755       __attribute__((annotate("moz_needs_no_vtable_type")))
 756 #    define MOZ_NON_MEMMOVABLE __attribute__((annotate("moz_non_memmovable")))
 757 #    define MOZ_NEEDS_MEMMOVABLE_TYPE \
 758       __attribute__((annotate("moz_needs_memmovable_type")))
 759 #    define MOZ_NEEDS_MEMMOVABLE_MEMBERS \
 760       __attribute__((annotate("moz_needs_memmovable_members")))
 761 #    define MOZ_NO_DANGLING_ON_TEMPORARIES \
 762       __attribute__((annotate("moz_no_dangling_on_temporaries")))
 763 #    define MOZ_INHERIT_TYPE_ANNOTATIONS_FROM_TEMPLATE_ARGS \
 764       __attribute__((                                       \
 765           annotate("moz_inherit_type_annotations_from_template_args")))
 766 #    define MOZ_NON_AUTOABLE __attribute__((annotate("moz_non_autoable")))
 767 #    define MOZ_INIT_OUTSIDE_CTOR
 768 #    define MOZ_IS_CLASS_INIT
 769 #    define MOZ_NON_PARAM __attribute__((annotate("moz_non_param")))
 770 #    define MOZ_REQUIRED_BASE_METHOD \
 771       __attribute__((annotate("moz_required_base_method")))
 772 #    define MOZ_MUST_RETURN_FROM_CALLER_IF_THIS_IS_ARG \
 773       __attribute__((annotate("moz_must_return_from_caller_if_this_is_arg")))
 774 #    define MOZ_MAY_CALL_AFTER_MUST_RETURN \
 775       __attribute__((annotate("moz_may_call_after_must_return")))
 776 #    define MOZ_LIFETIME_BOUND __attribute__((annotate("moz_lifetime_bound")))
 777 #    define MOZ_KNOWN_LIVE __attribute__((annotate("moz_known_live")))
 778 #    ifndef XGILL_PLUGIN
 779 #      define MOZ_UNANNOTATED __attribute__((annotate("moz_unannotated")))
 780 #      define MOZ_ANNOTATED __attribute__((annotate("moz_annotated")))
 781 #    else
 782 #      define MOZ_UNANNOTATED /* nothing */
 783 #      define MOZ_ANNOTATED   /* nothing */
 784 #    endif
 785
 786 /*
 787  * It turns out that clang doesn't like void func() __attribute__ {} without a
 788  * warning, so use pragmas to disable the warning.
 789  */
 790 #    ifdef __clang__
 791 #      define MOZ_HEAP_ALLOCATOR                                 \
 792         _Pragma("clang diagnostic push")                         \
 793             _Pragma("clang diagnostic ignored \"-Wgcc-compat\"") \
 794                 __attribute__((annotate("moz_heap_allocator")))  \
 795                 _Pragma("clang diagnostic pop")
 796 #    else
 797 #      define MOZ_HEAP_ALLOCATOR __attribute__((annotate("moz_heap_allocator")))
 798 #    endif
 799 #  else
 800 #    define MOZ_CAN_RUN_SCRIPT                              /* nothing */
 801 #    define MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION               /* nothing */
 802 #    define MOZ_CAN_RUN_SCRIPT_BOUNDARY                     /* nothing */
 803 #    define MOZ_MUST_OVERRIDE                               /* nothing */
 804 #    define MOZ_STATIC_CLASS                                /* nothing */
 805 #    define MOZ_STATIC_LOCAL_CLASS                          /* nothing */
 806 #    define MOZ_STACK_CLASS                                 /* nothing */
 807 #    define MOZ_NONHEAP_CLASS                               /* nothing */
 808 #    define MOZ_HEAP_CLASS                                  /* nothing */
 809 #    define MOZ_NON_TEMPORARY_CLASS                         /* nothing */
 810 #    define MOZ_TEMPORARY_CLASS                             /* nothing */
 811 #    define MOZ_TRIVIAL_CTOR_DTOR                           /* nothing */
 812 #    define MOZ_ALLOW_TEMPORARY                             /* nothing */
 813 #    define MOZ_ONLY_USED_TO_AVOID_STATIC_CONSTRUCTORS      /* nothing */
 814 #    define MOZ_IMPLICIT                                    /* nothing */
 815 #    define MOZ_IS_SMARTPTR_TO_REFCOUNTED                   /* nothing */
 816 #    define MOZ_IS_REFPTR                                   /* nothing */
 817 #    define MOZ_NO_ARITHMETIC_EXPR_IN_ARGUMENT              /* nothing */
 818 #    define MOZ_HEAP_ALLOCATOR                              /* nothing */
 819 #    define MOZ_OWNING_REF                                  /* nothing */
 820 #    define MOZ_NON_OWNING_REF                              /* nothing */
 821 #    define MOZ_UNSAFE_REF(reason)                          /* nothing */
 822 #    define MOZ_NO_ADDREF_RELEASE_ON_RETURN                 /* nothing */
 823 #    define MOZ_NEEDS_NO_VTABLE_TYPE                        /* nothing */
 824 #    define MOZ_NON_MEMMOVABLE                              /* nothing */
 825 #    define MOZ_NEEDS_MEMMOVABLE_TYPE                       /* nothing */
 826 #    define MOZ_NEEDS_MEMMOVABLE_MEMBERS                    /* nothing */
 827 #    define MOZ_NO_DANGLING_ON_TEMPORARIES                  /* nothing */
 828 #    define MOZ_INHERIT_TYPE_ANNOTATIONS_FROM_TEMPLATE_ARGS /* nothing */
 829 #    define MOZ_INIT_OUTSIDE_CTOR                           /* nothing */
 830 #    define MOZ_IS_CLASS_INIT                               /* nothing */
 831 #    define MOZ_NON_PARAM                                   /* nothing */
 832 #    define MOZ_NON_AUTOABLE                                /* nothing */
 833 #    define MOZ_REQUIRED_BASE_METHOD                        /* nothing */
 834 #    define MOZ_MUST_RETURN_FROM_CALLER_IF_THIS_IS_ARG      /* nothing */
 835 #    define MOZ_MAY_CALL_AFTER_MUST_RETURN                  /* nothing */
 836 #    define MOZ_LIFETIME_BOUND                              /* nothing */
 837 #    define MOZ_KNOWN_LIVE                                  /* nothing */
 838 #    define MOZ_UNANNOTATED                                 /* nothing */
 839 #    define MOZ_ANNOTATED                                   /* nothing */
 840 #  endif /* defined(MOZ_CLANG_PLUGIN) || defined(XGILL_PLUGIN) */
 841
 842 #  define MOZ_RAII MOZ_NON_TEMPORARY_CLASS MOZ_STACK_CLASS
 843
 844 // XGILL_PLUGIN is used for the GC rooting hazard analysis, which compiles with
 845 // gcc. gcc has different rules governing __attribute__((...)) placement, so
 846 // some attributes will error out when used in the source code where clang
 847 // expects them to be. Remove the problematic annotations when needed.
 848 //
 849 // The placement of c++11 [[...]] attributes is more flexible and defined by a
 850 // spec, so it would be nice to switch to those for the problematic
 851 // cases. Unfortunately, the official spec provides *no* way to annotate a
 852 // lambda function, which is one source of the difficulty here. It appears that
 853 // this will be fixed in c++23: https://github.com/cplusplus/papers/issues/882
 854
 855 #  ifdef XGILL_PLUGIN
 856
 857 #    undef MOZ_MUST_OVERRIDE
 858 #    undef MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION
 859 #    undef MOZ_CAN_RUN_SCRIPT
 860 #    undef MOZ_CAN_RUN_SCRIPT_BOUNDARY
 861 #    define MOZ_MUST_OVERRIDE                 /* nothing */
 862 #    define MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION /* nothing */
 863 #    define MOZ_CAN_RUN_SCRIPT                /* nothing */
 864 #    define MOZ_CAN_RUN_SCRIPT_BOUNDARY       /* nothing */
 865
 866 #  endif
 867
 868 #endif /* __cplusplus */
 869
 870 /**
 871  * Printf style formats.  MOZ_FORMAT_PRINTF and MOZ_FORMAT_WPRINTF can be used
 872  * to annotate a function or method that is "printf/wprintf-like"; this will let
 873  * (some) compilers check that the arguments match the template string.
 874  *
 875  * This macro takes two arguments.  The first argument is the argument
 876  * number of the template string.  The second argument is the argument
 877  * number of the '...' argument holding the arguments.
 878  *
 879  * Argument numbers start at 1.  Note that the implicit "this"
 880  * argument of a non-static member function counts as an argument.
 881  *
 882  * So, for a simple case like:
 883  *   void print_something (int whatever, const char *fmt, ...);
 884  * The corresponding annotation would be
 885  *   MOZ_FORMAT_PRINTF(2, 3)
 886  * However, if "print_something" were a non-static member function,
 887  * then the annotation would be:
 888  *   MOZ_FORMAT_PRINTF(3, 4)
 889  *
 890  * The second argument should be 0 for vprintf-like functions; that
 891  * is, those taking a va_list argument.
 892  *
 893  * Note that the checking is limited to standards-conforming
 894  * printf-likes, and in particular this should not be used for
 895  * PR_snprintf and friends, which are "printf-like" but which assign
 896  * different meanings to the various formats.
 897  *
 898  * MinGW requires special handling due to different format specifiers
 899  * on different platforms. The macro __MINGW_PRINTF_FORMAT maps to
 900  * either gnu_printf or ms_printf depending on where we are compiling
 901  * to avoid warnings on format specifiers that are legal.
 902  *
 903  * At time of writing MinGW has no wide equivalent to __MINGW_PRINTF_FORMAT;
 904  * therefore __MINGW_WPRINTF_FORMAT has been implemented following the same
 905  * pattern seen in MinGW's source.
 906  */
 907 #ifdef __MINGW32__
 908 #  define MOZ_FORMAT_PRINTF(stringIndex, firstToCheck) \
 909     __attribute__((format(__MINGW_PRINTF_FORMAT, stringIndex, firstToCheck)))
 910 #  ifndef __MINGW_WPRINTF_FORMAT
 911 #    if defined(__clang__)
 912 #      define __MINGW_WPRINTF_FORMAT wprintf
 913 #    elif defined(_UCRT) || __USE_MINGW_ANSI_STDIO
 914 #      define __MINGW_WPRINTF_FORMAT gnu_wprintf
 915 #    else
 916 #      define __MINGW_WPRINTF_FORMAT ms_wprintf
 917 #    endif
 918 #  endif
 919 #  define MOZ_FORMAT_WPRINTF(stringIndex, firstToCheck) \
 920     __attribute__((format(__MINGW_WPRINTF_FORMAT, stringIndex, firstToCheck)))
 921 #elif __GNUC__ || __clang__
 922 #  define MOZ_FORMAT_PRINTF(stringIndex, firstToCheck) \
 923     __attribute__((format(printf, stringIndex, firstToCheck)))
 924 #  define MOZ_FORMAT_WPRINTF(stringIndex, firstToCheck) \
 925     __attribute__((format(wprintf, stringIndex, firstToCheck)))
 926 #else
 927 #  define MOZ_FORMAT_PRINTF(stringIndex, firstToCheck)
 928 #  define MOZ_FORMAT_WPRINTF(stringIndex, firstToCheck)
 929 #endif
 930
 931 /**
 932  * To manually declare an XPCOM ABI-compatible virtual function, the following
 933  * macros can be used to handle the non-standard ABI used on Windows for COM
 934  * compatibility. E.g.:
 935  *
 936  *   virtual ReturnType MOZ_XPCOM_ABI foo();
 937  */
 938 #if defined(XP_WIN)
 939 #  define MOZ_XPCOM_ABI __stdcall
 940 #else
 941 #  define MOZ_XPCOM_ABI
 942 #endif
 943
 944 /**
 945  * MSVC / clang-cl don't optimize empty bases correctly unless we explicitly
 946  * tell it to, see:
 947  *
 948  * https://stackoverflow.com/questions/12701469/why-is-the-empty-base-class-optimization-ebo-is-not-working-in-msvc
 949  * https://devblogs.microsoft.com/cppblog/optimizing-the-layout-of-empty-base-classes-in-vs2015-update-2-3/
 950  */
 951 #if defined(_MSC_VER)
 952 #  define MOZ_EMPTY_BASES __declspec(empty_bases)
 953 #else
 954 #  define MOZ_EMPTY_BASES
 955 #endif
 956
 957 #endif /* mozilla_Attributes_h */