Actual source code: petscmacros.h

  1: #ifndef PETSC_PREPROCESSOR_MACROS_H
  2: #define PETSC_PREPROCESSOR_MACROS_H

  4: #include <petscconf.h>
  5: #include <petscconf_poison.h> /* for PetscDefined() error checking */

  7: /* SUBMANSEC = Sys */

  9: #if defined(__cplusplus)
 10:   #if __cplusplus <= 201103L
 11:     #define PETSC_CPP_VERSION 11
 12:   #elif __cplusplus <= 201402L
 13:     #define PETSC_CPP_VERSION 14
 14:   #elif __cplusplus <= 201703L
 15:     #define PETSC_CPP_VERSION 17
 16:   #elif __cplusplus <= 202002L
 17:     #define PETSC_CPP_VERSION 20
 18:   #else
 19:     #define PETSC_CPP_VERSION 22 // current year, or date of c++2b ratification
 20:   #endif
 21: #endif // __cplusplus

 23: #ifndef PETSC_CPP_VERSION
 24:   #define PETSC_CPP_VERSION 0
 25: #endif

 27: #if defined(__STDC_VERSION__)
 28:   #if __STDC_VERSION__ <= 199901L
 29:     // C99 except that 99 is >= 11 or 17 so we shorten it to 9 instead
 30:     #define PETSC_C_VERSION 9
 31:   #elif __STDC_VERSION__ <= 201112L
 32:     #define PETSC_C_VERSION 11
 33:   #elif __STDC_VERSION__ <= 201710L
 34:     #define PETSC_C_VERSION 17
 35:   #else
 36:     #define PETSC_C_VERSION 22 // current year, or date of c2b ratification
 37:   #endif
 38: #endif // __STDC_VERSION__

 40: #ifndef PETSC_C_VERSION
 41:   #define PETSC_C_VERSION 0
 42: #endif

 44: /* ========================================================================== */
 45: /* This facilitates using the C version of PETSc from C++ and the C++ version from C. */
 46: #if defined(__cplusplus)
 47:   #define PETSC_FUNCTION_NAME PETSC_FUNCTION_NAME_CXX
 48: #else
 49:   #define PETSC_FUNCTION_NAME PETSC_FUNCTION_NAME_C
 50: #endif

 52: /* ========================================================================== */
 53: /* Since PETSc manages its own extern "C" handling users should never include PETSc include
 54:  * files within extern "C". This will generate a compiler error if a user does put the include
 55:  * file within an extern "C".
 56:  */
 57: #if defined(__cplusplus)
 58: void assert_never_put_petsc_headers_inside_an_extern_c(int);
 59: void assert_never_put_petsc_headers_inside_an_extern_c(double);
 60: #endif

 62: #if defined(__cplusplus)
 63:   #define PETSC_RESTRICT PETSC_CXX_RESTRICT
 64: #else
 65:   #define PETSC_RESTRICT restrict
 66: #endif

 68: #define PETSC_INLINE        PETSC_DEPRECATED_MACRO("GCC warning \"PETSC_INLINE is deprecated (since version 3.17)\"") inline
 69: #define PETSC_STATIC_INLINE PETSC_DEPRECATED_MACRO("GCC warning \"PETSC_STATIC_INLINE is deprecated (since version 3.17)\"") static inline

 71: #if defined(_WIN32) && defined(PETSC_USE_SHARED_LIBRARIES) /* For Win32 shared libraries */
 72:   #define  __declspec(dllexport)
 73:   #define PETSC_DLLIMPORT __declspec(dllimport)
 74:   #define PETSC_VISIBILITY_INTERNAL
 75: #elif defined(__cplusplus) && defined(PETSC_USE_VISIBILITY_CXX)
 76:   #define            __attribute__((visibility("default")))
 77:   #define PETSC_DLLIMPORT           __attribute__((visibility("default")))
 78:   #define PETSC_VISIBILITY_INTERNAL __attribute__((visibility("hidden")))
 79: #elif !defined(__cplusplus) && defined(PETSC_USE_VISIBILITY_C)
 80:   #define            __attribute__((visibility("default")))
 81:   #define PETSC_DLLIMPORT           __attribute__((visibility("default")))
 82:   #define PETSC_VISIBILITY_INTERNAL __attribute__((visibility("hidden")))
 83: #else
 84:   #define 
 85:   #define PETSC_DLLIMPORT
 86:   #define PETSC_VISIBILITY_INTERNAL
 87: #endif

 89: #if defined(petsc_EXPORTS) /* CMake defines this when building the shared library */
 90:   #define PETSC_VISIBILITY_PUBLIC 
 91: #else /* Win32 users need this to import symbols from petsc.dll */
 92:   #define PETSC_VISIBILITY_PUBLIC PETSC_DLLIMPORT
 93: #endif

 95: /* Functions tagged with PETSC_EXTERN in the header files are always defined as extern "C" when
 96:  * compiled with C++ so they may be used from C and are always visible in the shared libraries
 97:  */
 98: #if defined(__cplusplus)
 99:   #define PETSC_EXTERN         extern "C" PETSC_VISIBILITY_PUBLIC
100:   #define PETSC_EXTERN_TYPEDEF extern "C"
101:   #define PETSC_INTERN         extern "C" PETSC_VISIBILITY_INTERNAL
102: #else
103:   #define PETSC_EXTERN extern PETSC_VISIBILITY_PUBLIC
104:   #define PETSC_EXTERN_TYPEDEF
105:   #define PETSC_INTERN extern PETSC_VISIBILITY_INTERNAL
106: #endif

108: #if defined(PETSC_USE_SINGLE_LIBRARY)
109:   #define PETSC_SINGLE_LIBRARY_INTERN PETSC_INTERN
110: #else
111:   #define PETSC_SINGLE_LIBRARY_INTERN PETSC_EXTERN
112: #endif

116: #endif

118: /*MC
119:   PetscHasAttribute - Determine whether a particular __attribute__ is supported by the compiler

121:   Synopsis:
122: #include <petscmacros.h>
123:   int PetscHasAttribute(name)

125:   Input Parameter:
126: . name - The name of the attribute to test

128:   Notes:
129:   name should be identical to what you might pass to the __attribute__ declaration itself --
130:   plain, unbroken text.

132:   As `PetscHasAttribute()` is wrapper over the function-like macro `__has_attribute()`, the
133:   exact type and value returned is implementation defined. In practice however, it usually
134:   returns `1` if the attribute is supported and `0` if the attribute is not supported.

136:   Example Usage:
137:   Typical usage is using the preprocessor

139: .vb
140:   #if PetscHasAttribute(always_inline)
141:   #  define MY_ALWAYS_INLINE __attribute__((always_inline))
142:   #else
143:   #  define MY_ALWAYS_INLINE
144:   #endif

146:   void foo(void) MY_ALWAYS_INLINE;
147: .ve

149:   but it can also be used in regular code

151: .vb
152:   if (PetscHasAttribute(some_attribute)) {
153:     foo();
154:   } else {
155:     bar();
156:   }
157: .ve

159:   Level: intermediate

161: .seealso: `PetscHasBuiltin()`, `PetscDefined()`, `PetscLikely()`, `PetscUnlikely()`,
162: `PETSC_ATTRIBUTE_FORMAT`
163: M*/
166: #endif
167: #define PetscHasAttribute(name) __has_attribute(name)

169: /*MC
170:   PetscHasBuiltin - Determine whether a particular builtin method is supported by the compiler

172:   Synopsis:
173: #include <petscmacros.h>
174:   int PetscHasBuiltin(name)

176:   Input Parameter:
177: . name - the name of the builtin routine

179:   Notes:
180:   Evaluates to `1` if the builtin is supported and `0` otherwise. Note the term "evaluates"
181:   (vs "expands") is deliberate; even though `PetscHasBuiltin()` is a macro the underlying
182:   detector is itself is a compiler extension with implementation-defined return type and
183:   semantics. Some compilers implement it as a macro, others as a compiler function. In practice
184:   however, all supporting compilers return an integer boolean as described.

186:   Example Usage:
187:   Typical usage is in preprocessor directives

189: .vb
190:   #if PetscHasBuiltin(__builtin_trap)
191:   __builtin_trap();
192:   #else
193:   abort();
194:   #endif
195: .ve

197:   But it may also be used in regular code

199: .vb
200:   if (PetscHasBuiltin(__builtin_alloca)) {
201:     foo();
202:   } else {
203:     bar();
204:   }
205: .ve

207:   Level: intermediate

209: .seealso: `PetscHasAttribute()`, `PetscAssume()`
210: M*/
213: #endif
214: // clangs __has_builtin prior to clang 10 did not properly handle non-function builtins such as
215: // __builtin_types_compatible_p which take types or other non-functiony things as
216: // arguments. The correct way to detect these then is to use __is_identifier (also a clang
217: // extension). GCC has always worked as expected. see https://stackoverflow.com/a/45043153
218: #if defined(__clang__) && defined(__clang_major__) && (__clang_major__ < 10) && defined(__is_identifier)
219:   #define PetscHasBuiltin(name) __is_identifier(name)
220: #else
221:   #define PetscHasBuiltin(name) __has_builtin(name)
222: #endif

224: #if !defined(PETSC_SKIP_ATTRIBUTE_MPI_TYPE_TAG)
225:   /*
226:    Support for Clang (>=3.2) matching type tag arguments with void* buffer types.
227:    This allows the compiler to detect cases where the MPI datatype argument passed to a MPI routine
228:    does not match the actual type of the argument being passed in
229: */
230:   #if PetscHasAttribute(pointer_with_type_tag)
231:     #define PETSC_ATTRIBUTE_MPI_POINTER_WITH_TYPE(bufno, typeno) __attribute__((pointer_with_type_tag(MPI, bufno, typeno)))
232:   #endif

234:   #if PetscHasAttribute(type_tag_for_datatype)
235:     #define PETSC_ATTRIBUTE_MPI_TYPE_TAG(type)                   __attribute__((type_tag_for_datatype(MPI, type)))
236:     #define PETSC_ATTRIBUTE_MPI_TYPE_TAG_LAYOUT_COMPATIBLE(type) __attribute__((type_tag_for_datatype(MPI, type, layout_compatible)))
237:   #endif
238: #endif // PETSC_SKIP_ATTRIBUTE_MPI_TYPE_TAG

240: #ifndef PETSC_ATTRIBUTE_MPI_POINTER_WITH_TYPE
241:   #define PETSC_ATTRIBUTE_MPI_POINTER_WITH_TYPE(bufno, typeno)
242: #endif

244: #ifndef PETSC_ATTRIBUTE_MPI_TYPE_TAG
245:   #define PETSC_ATTRIBUTE_MPI_TYPE_TAG(type)
246: #endif

248: #ifndef PETSC_ATTRIBUTE_MPI_TYPE_TAG_LAYOUT_COMPATIBLE
249:   #define PETSC_ATTRIBUTE_MPI_TYPE_TAG_LAYOUT_COMPATIBLE(type)
250: #endif

252: /*MC
253:   PETSC_ATTRIBUTE_FORMAT - Indicate to the compiler that specified arguments should be treated
254:   as format specifiers and checked for validity

256:   Synopsis:
257: #include <petscmacros.h>
258:   <attribute declaration> PETSC_ATTRIBUTE_FORMAT(int strIdx, int vaArgIdx)

260:   Input Parameters:
261: + strIdx   - The (1-indexed) location of the format string in the argument list
262: - vaArgIdx - The (1-indexed) location of the first formattable argument in the argument list

264:   Notes:
265:   This function attribute causes the compiler to issue warnings when the format specifier does
266:   not match the type of the variable that will be formatted, or when there exists a mismatch
267:   between the number of format specifiers and variables to be formatted. It is safe to use this
268:   macro if your compiler does not support format specifier checking (though this is
269:   exceeedingly rare).

271:   Both strIdx and vaArgIdx must be compile-time constant integer literals and cannot have the
272:   same value.

274:   The arguments to be formatted (and therefore checked by the compiler) must be "contiguous" in
275:   the argument list, that is, there is no way to indicate gaps which should not be checked.

277:   Definition is suppressed by defining `PETSC_SKIP_ATTRIBUTE_FORMAT` prior to including PETSc
278:   header files. In this case the macro will expand empty.

280:   Example Usage:
281: .vb
282:   // format string is 2nd argument, variable argument list containing args is 3rd argument
283:   void my_printf(void *obj, const char *fmt_string, ...) PETSC_ATTRIBUTE_FORMAT(2,3)

285:   int    x = 1;
286:   double y = 50.0;

288:   my_printf(NULL,"%g",x);      // WARNING, format specifier does not match for 'int'!
289:   my_printf(NULL,"%d",x,y);    // WARNING, more arguments than format specifiers!
290:   my_printf(NULL,"%d %g",x,y); // OK
291: .ve

293:   Level: developer

295: .seealso: `PETSC_ATTRIBUTE_COLD`, `PetscHasAttribute()`
296: M*/
297: #if PetscHasAttribute(format) && !defined(PETSC_SKIP_ATTRIBUTE_FORMAT)
298:   #define PETSC_ATTRIBUTE_FORMAT(strIdx, vaArgIdx) __attribute__((format(printf, strIdx, vaArgIdx)))
299: #else
300:   #define PETSC_ATTRIBUTE_FORMAT(strIdx, vaArgIdx)
301: #endif

303: /*MC
304:   PETSC_ATTRIBUTE_COLD - Indicate to the compiler that a function is very unlikely to be
305:   executed

307:   Notes:
308:   The marked function is often optimized for size rather than speed and may be grouped alongside
309:   other equally frigid routines improving code locality of lukewarm or hotter parts of program.

311:   The paths leading to cold functions are usually automatically marked as unlikely by the
312:   compiler. It may thus be useful to mark functions used to handle unlikely conditions -- such
313:   as error handlers -- as cold to improve optimization of the surrounding temperate functions.

315:   Example Usage:
316: .vb
317:   void my_error_handler(...) PETSC_ATTRIBUTE_COLD;

319:   if (temperature < 0) {
320:     return my_error_handler(...); // chilly!
321:   }
322: .ve

324:   Level: intermediate

326: .seealso: `PetscUnlikely()`, `PetscUnlikelyDebug()`, `PetscLikely()`, `PetscLikelyDebug()`,
327:           `PetscUnreachable()`, `PETSC_ATTRIBUTE_FORMAT`
328: M*/
329: #if PetscHasAttribute(__cold__)
330:   #define PETSC_ATTRIBUTE_COLD __attribute__((__cold__))
331: #elif PetscHasAttribute(cold) /* some implementations (old gcc) use no underscores */
332:   #define PETSC_ATTRIBUTE_COLD __attribute__((cold))
333: #else
334:   #define PETSC_ATTRIBUTE_COLD
335: #endif

337: /*MC
338:   PETSC_NULLPTR - Standard way of indicating a null value or pointer

340:   Notes:
341:   Equivalent to NULL in C source, and nullptr in C++ source. Note that for the purposes of
342:   interoperability between C and C++, setting a pointer to `PETSC_NULLPTR` in C++ is functonially
343:   equivalent to setting the same pointer to NULL in C. That is to say that the following
344:   expressions are equivalent\:

346: .vb
347:   ptr == PETSC_NULLPTR
348:   ptr == NULL
349:   ptr == 0
350:   !ptr

352:   ptr = PETSC_NULLPTR
353:   ptr = NULL
354:   ptr = 0
355: .ve

357:   and for completeness' sake\:

359: .vb
360:   PETSC_NULLPTR == NULL
361: .ve

363:   Fortran Notes:
364:   Not available in Fortran

366:   Example Usage:
367: .vb
368:   // may be used in place of '\0' or other such teminators in the definition of char arrays
369:   const char *const MyEnumTypes[] = {
370:     "foo",
371:     "bar",
372:     PETSC_NULLPTR
373:   };

375:   // may be used to nullify objects
376:   PetscObject obj = PETSC_NULLPTR;

378:   // may be used in any function expecting NULL
379:   PetscInfo(PETSC_NULLPTR,"Lorem Ipsum Dolor");
380: .ve

382:   Developer Notes:
383:   `PETSC_NULLPTR` must be used in place of NULL in all C++ source files. Using NULL in source
384:   files compiled with a C++ compiler may lead to unexpected side-effects in function overload
385:   resolution and/or compiler warnings.

387:   Level: beginner

389: .seealso: `PETSC_CONSTEXPR_14`, `PETSC_NODISCARD`
390: M*/

392: /*MC
393:   PETSC_CONSTEXPR_14 - C++14 constexpr

395:   Notes:
396:   Equivalent to constexpr when using a C++ compiler that supports C++14. Expands to nothing
397:   if the C++ compiler does not support C++14 or when not compiling with a C++ compiler. Note
398:   that this cannot be used in cases where an empty expansion would result in invalid code. It
399:   is safe to use this in C source files.

401:   Fortran Notes:
402:   Not available in Fortran

404:   Example Usage:
405: .vb
406:   PETSC_CONSTEXPR_14 int factorial(int n)
407:   {
408:     int r = 1;

410:     do {
411:       r *= n;
412:     } while (--n);
413:     return r;
414:   }
415: .ve

417:   Level: beginner

419: .seealso: `PETSC_NULLPTR`, `PETSC_NODISCARD`
420: M*/

422: /*MC
423:   PETSC_NODISCARD - Mark the return value of a function as non-discardable

425:   Not available in Fortran

427:   Level: beginner

429:   Notes:
430:   Hints to the compiler that the return value of a function must be captured. A diagnostic may
431:   (but is not required to) be emitted if the value is discarded. It is safe to use this in both
432:   C and C++ source files.

434:   Example Usage:
435: .vb
436:   class Foo
437:   {
438:     int x;

440:   public:
441:     PETSC_NODISCARD Foo(int y) : x(y) { }
442:   };

444:   PETSC_NODISCARD int factorial(int n)
445:   {
446:     return n <= 1 ? 1 : (n * factorial(n - 1));
447:   }

449:   auto x = factorial(10); // OK, capturing return value
450:   factorial(10);          // Warning: ignoring return value of function declared 'nodiscard'

452:   auto f = Foo(x); // OK, capturing constructed object
453:   Foo(x);          // Warning: Ignoring temporary created by a constructor declared 'nodiscard'
454: .ve

456: .seealso: `PETSC_NULLPTR`, `PETSC_CONSTEXPR_14`
457: M*/

459: /* C++11 features */
460: #if defined(__cplusplus) || (PETSC_C_VERSION >= 23)
461:   #define PETSC_NULLPTR nullptr
462: #else
463:   #define PETSC_NULLPTR NULL
464: #endif

466: /* C++14 features */
467: #if PETSC_CPP_VERSION >= 14
468:   #define PETSC_CONSTEXPR_14 constexpr
469: #else
470:   #define PETSC_CONSTEXPR_14
471: #endif

473: /* C++17 features */
474: #if PETSC_CPP_VERSION >= 17
475:   #define PETSC_CONSTEXPR_17 constexpr
476: #else
477:   #define PETSC_CONSTEXPR_17
478: #endif

480: #if (PETSC_CPP_VERSION >= 17) || (PETSC_C_VERSION >= 23)
481:   #define PETSC_NODISCARD [[nodiscard]]
482: #elif PetscHasAttribute(warn_unused_result)
483:   #define PETSC_NODISCARD __attribute__((warn_unused_result))
484: #else
485:   #define PETSC_NODISCARD
486: #endif

488: #include <petscversion.h>
489: #define PETSC_AUTHOR_INFO "       The PETSc Team\n    petsc-maint@mcs.anl.gov\n https://petsc.org/\n"

491: /* designated initializers since C99 and C++20, MSVC never supports them though */
492: #if defined(_MSC_VER) || (defined(__cplusplus) && (PETSC_CPP_VERSION < 20))
493:   #define PetscDesignatedInitializer(name, ...) __VA_ARGS__
494: #else
495:   #define PetscDesignatedInitializer(name, ...) .name = __VA_ARGS__
496: #endif

498: /*MC
499:   PetscUnlikely - Hints the compiler that the given condition is usually false

501:   Synopsis:
502: #include <petscmacros.h>
503:   bool PetscUnlikely(bool cond)

505:   Not Collective

507:   Input Parameter:
508: . cond - Boolean expression

510:   Notes:
511:   Not available from fortran.

513:   This returns the same truth value, it is only a hint to compilers that the result of cond is
514:   unlikely to be true.

516:   Example usage:
517: .vb
518:   if (PetscUnlikely(cond)) {
519:     foo(); // cold path
520:   } else {
521:     bar(); // hot path
522:   }
523: .ve

525:   Level: advanced

527: .seealso: `PetscLikely()`, `PetscUnlikelyDebug()`, `PetscCall()`, `PetscDefined()`, `PetscHasAttribute()`,
528:           `PETSC_ATTRIBUTE_COLD`
529: M*/

531: /*MC
532:   PetscLikely - Hints the compiler that the given condition is usually true

534:   Synopsis:
535: #include <petscmacros.h>
536:   bool PetscLikely(bool cond)

538:   Not Collective

540:   Input Parameter:
541: . cond - Boolean expression

543:   Notes:
544:   Not available from fortran.

546:   This returns the same truth value, it is only a hint to compilers that the result of cond is
547:   likely to be true.

549:   Example usage:
550: .vb
551:   if (PetscLikely(cond)) {
552:     foo(); // hot path
553:   } else {
554:     bar(); // cold path
555:   }
556: .ve

558:   Level: advanced

560: .seealso: `PetscUnlikely()`, `PetscDefined()`, `PetscHasAttribute()`
561:           `PETSC_ATTRIBUTE_COLD`
562: M*/
563: #if defined(PETSC_HAVE_BUILTIN_EXPECT)
564:   #define PetscUnlikely(cond) __builtin_expect(!!(cond), 0)
565:   #define PetscLikely(cond)   __builtin_expect(!!(cond), 1)
566: #else
567:   #define PetscUnlikely(cond) (cond)
568:   #define PetscLikely(cond)   (cond)
569: #endif

571: /*MC
572:   PetscUnreachable - Indicate to the compiler that a code-path is logically unreachable

574:   Synopsis:
575: #include <petscmacros.h>
576:   void PetscUnreachable(void)

578:   Notes:
579:   Indicates to the compiler (usually via some built-in) that a particular code path is always
580:   unreachable. Behavior is undefined if this function is ever executed, the user can expect an
581:   unceremonious crash.

583:   Example usage:
584:   Useful in situations such as switches over enums where not all enumeration values are
585:   explicitly covered by the switch

587: .vb
588:   typedef enum {RED, GREEN, BLUE} Color;

590:   int foo(Color c)
591:   {
592:     // it is known to programmer (or checked previously) that c is either RED or GREEN
593:     // but compiler may not be able to deduce this and/or emit spurious warnings
594:     switch (c) {
595:       case RED:
596:         return bar();
597:       case GREEN:
598:         return baz();
599:       default:
600:         PetscUnreachable(); // program is ill-formed if executed
601:     }
602:   }
603: .ve

605:   Level: advanced

607: .seealso: `SETERRABORT()`, `PETSCABORT()`, `PETSC_ATTRIBUTE_COLD`, `PetscAssume()`
608: M*/
609: #if PETSC_CPP_VERSION >= 23
610:   #include <utility>
611:   #define PetscUnreachable() std::unreachable()
612: #elif defined(__GNUC__)
613:   /* GCC 4.8+, Clang, Intel and other compilers compatible with GCC (-std=c++0x or above) */
614:   #define PetscUnreachable() __builtin_unreachable()
615: #elif defined(_MSC_VER) /* MSVC */
616:   #define PetscUnreachable() __assume(0)
617: #else /* ??? */
618:   #define PetscUnreachable() SETERRABORT(PETSC_COMM_SELF, PETSC_ERR_PLIB, "Code path explicitly marked as unreachable executed")
619: #endif

621: /*MC
622:   PetscAssume - Indicate to the compiler a condition that is defined to be true

624:   Synopsis:
625: #include <petscmacros.h>
626:   void PetscAssume(bool cond)

628:   Input Parameter:
629: . cond - Boolean expression

631:   Notes:
632:   If supported by the compiler, `cond` is used to inform the optimizer of an invariant
633:   truth. The argument itself is never evaluated, so any side effects of the expression will be
634:   discarded. This macro is used in `PetscAssert()` to retain information gained from debug
635:   checks that would be lost in optimized builds. For example\:

637: .vb
638:   PetscErrorCode foo(PetscInt x) {

640:     PetscAssert(x >= 0, ...);
641:   }
642: .ve

644:   The assertion checks that `x` is positive when debugging is enabled (and returns from `foo()`
645:   if it is not). This implicitly informs the optimizer that `x` cannot be negative. However,
646:   when debugging is disabled any `PetscAssert()` checks are tautologically false, and hence the
647:   optimizer cannot deduce any information from them.

649:   Due to compiler limitations `PetscAssume()` works best when `cond` involves
650:   constants. Certain compilers do not yet propagate symbolic inequalities i.e.\:

652: .vb
653:   int a, b, var_five;

655:   // BEST, all supporting compilers will understand a cannot be >= 5
656:   PetscAssume(a < 5);

658:    // OK, some compilers may understand that a cannot be >= 5
659:   PetscAssume(a <= b && b < 5);

661:    // WORST, most compilers will not get the memo
662:   PetscAssume(a <= b && b < var_five);
663: .ve

665:   If the condition is violated at runtime then behavior is wholly undefined. If the
666:   condition is violated at compile-time, the condition "supersedes" the compile-time violation
667:   and the program is ill-formed, no diagnostic required. For example consider the following\:

669: .vb
670:   PetscInt x = 0;

672:   PetscAssume(x != 0);
673:   if (x == 0) {
674:     x += 10;
675:   } else {
676:     popen("rm -rf /", "w");
677:   }
678: .ve

680:   Even though `x` is demonstrably `0` the compiler may opt to\:

682:   - emit an unconditional `popen("rm -rf /", "w")`
683:   - ignore `PetscAssume()` altogether and emit the correct path of `x += 10`
684:   - reformat the primary disk partition

686:   Level: advanced

688: .seealso: `PetscAssert()`
689: M*/
690: #if PETSC_CPP_VERSION >= 23
691:   #define PetscAssume(...) [[assume(__VA_ARGS__)]]
692: #elif defined(_MSC_VER) // msvc
693:   #define PetscAssume(...) __assume(__VA_ARGS__)
694: #elif defined(__clang__) && PetscHasBuiltin(__builtin_assume) // clang
695:   #define PetscAssume(...) \
696:     do { \
697:       _Pragma("clang diagnostic push"); \
698:       _Pragma("clang diagnostic ignored \"-Wassume\""); \
699:       __builtin_assume(__VA_ARGS__); \
700:       _Pragma("clang diagnostic pop"); \
701:     } while (0)
702: #else // gcc (and really old clang)
703:   // gcc does not have its own __builtin_assume() intrinsic. One could fake it via
704:   //
705:   // if (PetscUnlikely(!cond)) PetscUnreachable();
706:   //
707:   // but this it unsavory because the side effects of cond are not guaranteed to be
708:   // discarded. Though in most circumstances gcc will optimize out the if (because any evaluation
709:   // for which cond is false would be undefined results in undefined behavior anyway) it cannot
710:   // always do so. This is especially the case for opaque or non-inline function calls:
711:   //
712:   // extern int bar(int);
713:   //
714:   // int foo(int x) {
715:   //   PetscAssume(bar(x) == 2);
716:   //   if (bar(x) == 2) {
717:   //     return 1;
718:   //   } else {
719:   //     return 0;
720:   //   }
721:   // }
722:   //
723:   // Here gcc would (if just using builtin_expect()) emit 2 calls to bar(). Note we still have
724:   // cond "tested" in the condition, but this is done to silence unused-but-set variable warnings
725:   #define PetscAssume(...) \
726:     do { \
727:       if (0 && (__VA_ARGS__)) PetscUnreachable(); \
728:     } while (0)
729: #endif

731: /*MC
732:   PetscExpand - Expand macro argument

734:   Synopsis:
735: #include <petscmacros.h>
736:   <macro-expansion> PetscExpand(x)

738:   Input Parameter:
739: . x - The preprocessor token to expand

741:   Level: beginner

743: .seealso: `PetscStringize()`, `PetscConcat()`
744: M*/
745: #define PetscExpand_(...) __VA_ARGS__
746: #define PetscExpand(...)  PetscExpand_(__VA_ARGS__)

748: /*MC
749:   PetscStringize - Stringize a token

751:   Synopsis:
752: #include <petscmacros.h>
753:   const char* PetscStringize(x)

755:   Input Parameter:
756: . x - The token you would like to stringize

758:   Output Parameter:
759: . <return-value> - The string representation of x

761:   Notes:
762:   Not available from Fortran.

764:   PetscStringize() expands x before stringizing it, if you do not wish to do so, use
765:   PetscStringize_() instead.

767:   Example Usage:
768: .vb
769:   #define MY_OTHER_VAR hello there
770:   #define MY_VAR       MY_OTHER_VAR

772:   PetscStringize(MY_VAR)  -> "hello there"
773:   PetscStringize_(MY_VAR) -> "MY_VAR"

775:   int foo;
776:   PetscStringize(foo)  -> "foo"
777:   PetscStringize_(foo) -> "foo"
778: .ve

780:   Level: beginner

782: .seealso: `PetscConcat()`, `PetscExpandToNothing()`, `PetscExpand()`
783: M*/
784: #define PetscStringize_(...) #__VA_ARGS__
785: #define PetscStringize(...)  PetscStringize_(__VA_ARGS__)

787: /*MC
788:   PetscConcat - Concatenate two tokens

790:   Synopsis:
791: #include <petscmacros.h>
792:   <macro-expansion> PetscConcat(x, y)

794:   Input Parameters:
795: + x - First token
796: - y - Second token

798:   Notes:
799:   Not available from Fortran.

801:   PetscConcat() will expand both arguments before pasting them together, use PetscConcat_()
802:   if you don't want to expand them.

804:   Example usage:
805: .vb
806:   PetscConcat(hello,there) -> hellothere

808:   #define HELLO hello
809:   PetscConcat(HELLO,there)  -> hellothere
810:   PetscConcat_(HELLO,there) -> HELLOthere
811: .ve

813:   Level: beginner

815: .seealso: `PetscStringize()`, `PetscExpand()`
816: M*/
817: #define PetscConcat_(x, y) x##y
818: #define PetscConcat(x, y)  PetscConcat_(x, y)

820: #define PETSC_INTERNAL_COMPL_0 1
821: #define PETSC_INTERNAL_COMPL_1 0

823: /*MC
824:   PetscCompl - Expands to the integer complement of its argument

826:   Synopsis:
827: #include <petscmacros.h>
828:   int PetscCompl(b)

830:   Input Parameter:
831: . b - Preprocessor variable, must expand to either integer literal 0 or 1

833:   Output Parameter:
834: . <return-value> - Either integer literal 0 or 1

836:   Notes:
837:   Not available from Fortran.

839:   Expands to integer literal 0 if b expands to 1, or integer literal 1 if b expands to
840:   0. Behaviour is undefined if b expands to anything else. PetscCompl() will expand its
841:   argument before returning the complement.

843:   This macro can be useful for negating PetscDefined() inside macros e.g.

845: $ #define PETSC_DONT_HAVE_FOO PetscCompl(PetscDefined(HAVE_FOO))

847:   Example usage:
848: .vb
849:   #define MY_VAR 1
850:   PetscCompl(MY_VAR) -> 0

852:   #undef  MY_VAR
853:   #define MY_VAR 0
854:   PetscCompl(MY_VAR) -> 1
855: .ve

857:   Level: beginner

859: .seealso: `PetscConcat()`, `PetscDefined()`
860: M*/
861: #define PetscCompl(b) PetscConcat_(PETSC_INTERNAL_COMPL_, PetscExpand(b))

863: #if !defined(PETSC_SKIP_VARIADIC_MACROS)
864:   /*MC
865:   PetscDefined - Determine whether a boolean macro is defined

867:   Synopsis:
868: #include <petscmacros.h>
869:   int PetscDefined(def)

871:   Input Parameter:
872: . def - PETSc-style preprocessor variable (without PETSC_ prepended!)

874:   Output Parameter:
875: . <return-value> - Either integer literal 0 or 1

877:   Notes:
878:   Not available from Fortran, requires variadic macro support, definition is disabled by
879:   defining `PETSC_SKIP_VARIADIC_MACROS`.

881:   `PetscDefined()` returns 1 if and only if "PETSC_ ## def" is defined (but empty) or defined to
882:   integer literal 1. In all other cases, `PetscDefined()` returns integer literal 0. Therefore
883:   this macro should not be used if its argument may be defined to a non-empty value other than
884:   1.

886:   The prefix "PETSC_" is automatically prepended to def. To avoid prepending "PETSC_", say to
887:   add custom checks in user code, one should use `PetscDefined_()`.

889: $ #define FooDefined(d) PetscDefined_(PetscConcat(FOO_,d))

891:   Developer Notes:
892:   Getting something that works in C and CPP for an arg that may or may not be defined is
893:   tricky. Here, if we have "#define PETSC_HAVE_BOOGER 1" we match on the placeholder define,
894:   insert the "0," for arg1 and generate the triplet (0, 1, 0). Then the last step cherry picks
895:   the 2nd arg (a one). When PETSC_HAVE_BOOGER is not defined, we generate a (... 1, 0) pair,
896:   and when the last step cherry picks the 2nd arg, we get a zero.

898:   Our extra expansion via PetscDefined__take_second_expand() is needed with MSVC, which has a
899:   nonconforming implementation of variadic macros.

901:   Example Usage:
902:   Suppose you would like to call either "foo()" or "bar()" depending on whether PETSC_USE_DEBUG
903:   is defined then

905: .vb
906:   #if PetscDefined(USE_DEBUG)
907:     foo();
908:   #else
909:     bar();
910:   #endif

912:   // or alternatively within normal code
913:   if (PetscDefined(USE_DEBUG)) {
914:     foo();
915:   } else {
916:     bar();
917:   }
918: .ve

920:   is equivalent to

922: .vb
923:   #if defined(PETSC_USE_DEBUG)
924:   #  if MY_DETECT_EMPTY_MACRO(PETSC_USE_DEBUG) // assuming you have such a macro
925:        foo();
926:   #   elif PETSC_USE_DEBUG == 1
927:        foo();
928:   #   else
929:        bar();
930:   #  endif
931:   #else
932:   bar();
933:   #endif
934: .ve

936:   Level: intermediate

938: .seealso: `PetscHasAttribute()`, `PetscUnlikely()`, `PetscLikely()`, `PetscConcat()`,
939:           `PetscExpandToNothing()`, `PetscCompl()`
940: M*/
941:   #define PetscDefined_arg_1                                    shift,
942:   #define PetscDefined_arg_                                     shift,
943:   #define PetscDefined__take_second_expanded(ignored, val, ...) val
944:   #define PetscDefined__take_second_expand(args)                PetscDefined__take_second_expanded args
945:   #define PetscDefined__take_second(...)                        PetscDefined__take_second_expand((__VA_ARGS__))
946:   #define PetscDefined__(arg1_or_junk)                          PetscDefined__take_second(arg1_or_junk 1, 0, at_)
947:   #define PetscDefined_(value)                                  PetscDefined__(PetscConcat_(PetscDefined_arg_, value))
948:   #define PetscDefined(def)                                     PetscDefined_(PetscConcat(PETSC_, def))

950:   /*MC
951:   PetscUnlikelyDebug - Hints the compiler that the given condition is usually false, eliding
952:   the check in optimized mode

954:   Synopsis:
955: #include <petscmacros.h>
956:   bool PetscUnlikelyDebug(bool cond)

958:   Not Collective

960:   Input Parameters:
961: . cond - Boolean expression

963:   Notes:
964:   Not available from Fortran, requires variadic macro support, definition is disabled by
965:   defining `PETSC_SKIP_VARIADIC_MACROS`.

967:   This returns the same truth value, it is only a hint to compilers that the result of cond is
968:   likely to be false. When PETSc is compiled in optimized mode this will always return
969:   false. Additionally, cond is guaranteed to not be evaluated when PETSc is compiled in
970:   optimized mode.

972:   Example usage:
973:   This routine is shorthand for checking both the condition and whether PetscDefined(USE_DEBUG)
974:   is true. So

976: .vb
977:   if (PetscUnlikelyDebug(cond)) {
978:     foo();
979:   } else {
980:     bar();
981:   }
982: .ve

984:   is equivalent to

986: .vb
987:   if (PetscDefined(USE_DEBUG)) {
988:     if (PetscUnlikely(cond)) {
989:       foo();
990:     } else {
991:       bar();
992:     }
993:   } else {
994:     bar();
995:   }
996: .ve

998:   Level: advanced

1000: .seealso: `PetscUnlikely()`, `PetscLikely()`, `PetscCall()`, `SETERRQ`
1001: M*/
1002:   #define PetscUnlikelyDebug(cond) (PetscDefined(USE_DEBUG) && PetscUnlikely(cond))

1004:   #if defined(PETSC_CLANG_STATIC_ANALYZER)
1005:     // silence compiler warnings when using -pedantic, this is only used by the linter and it cares
1006:     // not what ISO C allows
1007:     #define PetscMacroReturns_(retexpr, ...) \
1008:       __extension__({ \
1009:         __VA_ARGS__; \
1010:         retexpr; \
1011:       })
1012:   #else
1013:     #define PetscMacroReturns_(retexpr, ...) \
1014:       retexpr; \
1015:       do { \
1016:         __VA_ARGS__; \
1017:       } while (0)
1018:   #endif

1020:   /*MC
1021:   PetscExpandToNothing - Expands to absolutely nothing at all

1023:   Synopsis:
1024: #include <petscmacros.h>
1025:   void PetscExpandToNothing(...)

1027:   Input Parameter:
1028: . __VA_ARGS__ - Anything at all

1030:   Notes:
1031:   Not available from Fortran, requires variadic macro support, definition is disabled by
1032:   defining `PETSC_SKIP_VARIADIC_MACROS`.

1034:   Must have at least 1 parameter.

1036:   Example usage:
1037: .vb
1038:   PetscExpandToNothing(a,b,c) -> *nothing*
1039: .ve

1041:   Level: beginner

1043: .seealso: `PetscConcat()`, `PetscDefined()`, `PetscStringize()`, `PetscExpand()`
1044: M*/
1045:   #define PetscExpandToNothing(...)

1047:   /*MC
1048:   PetscMacroReturns - Define a macro body that returns a value

1050:   Synopsis:
1051: #include <petscmacros.h>
1052:   return_type PetscMacroReturns(return_type retexpr, ...)

1054:   Input Parameters:
1055: + retexpr     - The value or expression that the macro should return
1056: - __VA_ARGS__ - The body of the macro

1058:   Notes:
1059:   Due to limitations of the C-preprocessor retexpr cannot depend on symbols declared in the
1060:   body of the macro and should not depend on values produced as a result of the expression. The
1061:   user should not assume that the result of this macro is equivalent to a single logical source
1062:   line. It is not portable to use macros defined using this one in conditional or loop bodies
1063:   without enclosing them in curly braces\:

1065: .vb
1066:   #define FOO(arg1) PetscMacroReturns(0,arg1+=10) // returns 0

1068:   int err,x = 10;

1070:   if (...) err = FOO(x);      // ERROR, body of FOO() executed outside the if statement
1071:   if (...) { err = FOO(x); }  // OK

1073:   for (...) err = FOO(x);     // ERROR, body of FOO() executed outside the loop
1074:   for (...) { err = FOO(x); } // OK
1075: .ve

1077:   It is also not portable to use this macro directly inside function call, conditional, loop,
1078:   or switch statements\:

1080: .vb
1081:   extern void bar(int);

1083:   int ret = FOO(x);

1085:   bar(FOO(x)); // ERROR, may not compile
1086:   bar(ret);    // OK

1088:   if (FOO(x))  // ERROR, may not compile
1089:   if (ret)     // OK
1090: .ve

1092:   Example usage:
1093: .vb
1094:   #define MY_SIMPLE_RETURNING_MACRO(arg1) PetscMacroReturns(0,arg1+=10)

1096:   int x = 10;
1097:   int err = MY_SIMPLE_RETURNING_MACRO(x); // err = 0, x = 20

1099:   // multiline macros allowed, but must declare with line continuation as usual
1100:   #define MY_COMPLEX_RETURNING_MACRO(arg1) PetscMacroReturns(0, \
1101:     if (arg1 > 10) {                                            \
1102:       puts("big int!");                                         \
1103:     } else {                                                    \
1104:       return 7355608;                                           \
1105:     }                                                           \
1106:   )

1108:   // if retexpr contains commas, must enclose it with braces
1109:   #define MY_COMPLEX_RETEXPR_MACRO_1() PetscMacroReturns(x+=10,0,body...)
1110:   #define MY_COMPLEX_RETEXPR_MACRO_2() PetscMacroReturns((x+=10,0),body...)

1112:   int x = 10;
1113:   int y = MY_COMPLEX_RETEXPR_MACRO_1(); // ERROR, y = x = 20 not 0
1114:   int z = MY_COMPLEX_RETEXPR_MACRO_2(); // OK, y = 0, x = 20
1115: .ve

1117:   Level: intermediate

1119: .seealso: `PetscExpand()`, `PetscConcat()`, `PetscStringize()`
1120: M*/
1121:   #define PetscMacroReturns(retexpr, ...) PetscMacroReturns_(retexpr, __VA_ARGS__)

1123:   #define PetscMacroReturnStandard(...) PetscMacroReturns(PETSC_SUCCESS, __VA_ARGS__)

1125: #endif /* !PETSC_SKIP_VARIADIC_MACROS */

1127: /*MC
1128:   PETSC_STATIC_ARRAY_LENGTH - Return the length of a static array

1130:   Level: intermediate
1131: M*/
1132: #define PETSC_STATIC_ARRAY_LENGTH(a) (sizeof(a) / sizeof((a)[0]))

1134: /*
1135:   These macros allow extracting out the first argument or all but the first argument from a macro __VAR_ARGS__ INSIDE another macro.

1137:   Example usage:

1139:   #define mymacro(obj,...) {
1140:     PETSC_FIRST_ARG((__VA_ARGS__,unused));
1141:     f(22 PETSC_REST_ARG(__VA_ARGS__));
1142:   }

1144:   Note you add a dummy extra argument to __VA_ARGS__ and enclose them in an extra set of () for PETSC_FIRST_ARG() and PETSC_REST_ARG(__VA_ARGS__) automatically adds a leading comma only if there are additional arguments

1146:   Reference:
1147:   https://stackoverflow.com/questions/5588855/standard-alternative-to-gccs-va-args-trick
1148: */
1149: #define PETSC_FIRST_ARG_(N, ...)                                                                      N
1150: #define PETSC_FIRST_ARG(args)                                                                         PETSC_FIRST_ARG_ args
1151: #define PETSC_SELECT_16TH(a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15, a16, ...) a16
1152: #define PETSC_NUM(...)                                                                                PETSC_SELECT_16TH(__VA_ARGS__, TWOORMORE, TWOORMORE, TWOORMORE, TWOORMORE, TWOORMORE, TWOORMORE, TWOORMORE, TWOORMORE, TWOORMORE, TWOORMORE, TWOORMORE, TWOORMORE, TWOORMORE, TWOORMORE, ONE, throwaway)
1153: #define PETSC_REST_HELPER_TWOORMORE(first, ...)                                                       , __VA_ARGS__
1154: #define PETSC_REST_HELPER_ONE(first)
1155: #define PETSC_REST_HELPER2(qty, ...) PETSC_REST_HELPER_##qty(__VA_ARGS__)
1156: #define PETSC_REST_HELPER(qty, ...)  PETSC_REST_HELPER2(qty, __VA_ARGS__)
1157: #define PETSC_REST_ARG(...)          PETSC_REST_HELPER(PETSC_NUM(__VA_ARGS__), __VA_ARGS__)

1159: #endif /* PETSC_PREPROCESSOR_MACROS_H */