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`, `PETSC_ATTRIBUTE_MAY_ALIAS`
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:   Level: developer

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

273:   Both `strIdx` and `vaArgIdx` must be compile-time constant integer literals and cannot have the
274:   same value.

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

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

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

287:   int    x = 1;
288:   double y = 50.0;

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

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:   Level: intermediate

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

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

317:   Example Usage:
318: .vb
319:   void my_error_handler(...) PETSC_ATTRIBUTE_COLD;

321:   if (temperature < 0) {
322:     return my_error_handler(...); // chilly!
323:   }
324: .ve

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_ATTRIBUTE_MAY_ALIAS - Indicate to the compiler that a type is not
339:   subjected to type-based alias analysis, but is instead assumed to be able to
340:   alias any other type of objects

342:   Example Usage:
343: .vb
344:   typedef PetscScalar PetscScalarAlias PETSC_ATTRIBUTE_MAY_ALIAS;

346:   PetscReal        *pointer;
347:   PetscScalarAlias *other_pointer = reinterpret_cast<PetscScalarAlias *>(pointer);
348: .ve

350:   Level: advanced

352: .seealso: `PetscHasAttribute()`
353: M*/
354: #if PetscHasAttribute(may_alias) && !defined(PETSC_SKIP_ATTRIBUTE_MAY_ALIAS)
355:   #define PETSC_ATTRIBUTE_MAY_ALIAS __attribute__((may_alias))
356: #else
357:   #define PETSC_ATTRIBUTE_MAY_ALIAS
358: #endif

360: /*MC
361:   PETSC_NULLPTR - Standard way of indicating a null value or pointer

363:   No Fortran Support

365:   Level: beginner

367:   Notes:
368:   Equivalent to `NULL` in C source, and `nullptr` in C++ source. Note that for the purposes of
369:   interoperability between C and C++, setting a pointer to `PETSC_NULLPTR` in C++ is functonially
370:   equivalent to setting the same pointer to `NULL` in C. That is to say that the following
371:   expressions are equivalent\:

373: .vb
374:   ptr == PETSC_NULLPTR
375:   ptr == NULL
376:   ptr == 0
377:   !ptr

379:   ptr = PETSC_NULLPTR
380:   ptr = NULL
381:   ptr = 0
382: .ve

384:   and for completeness' sake\:

386: .vb
387:   PETSC_NULLPTR == NULL
388: .ve

390:   Example Usage:
391: .vb
392:   // may be used in place of '\0' or other such teminators in the definition of char arrays
393:   const char *const MyEnumTypes[] = {
394:     "foo",
395:     "bar",
396:     PETSC_NULLPTR
397:   };

399:   // may be used to nullify objects
400:   PetscObject obj = PETSC_NULLPTR;

402:   // may be used in any function expecting NULL
403:   PetscInfo(PETSC_NULLPTR,"Lorem Ipsum Dolor");
404: .ve

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

411: .seealso: `PETSC_CONSTEXPR_14`, `PETSC_NODISCARD`
412: M*/

414: /*MC
415:   PETSC_CONSTEXPR_14 - C++14 constexpr

417:   No Fortran Support

419:   Level: beginner

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

427:   Example Usage:
428: .vb
429:   PETSC_CONSTEXPR_14 int factorial(int n)
430:   {
431:     int r = 1;

433:     do {
434:       r *= n;
435:     } while (--n);
436:     return r;
437:   }
438: .ve

440: .seealso: `PETSC_NULLPTR`, `PETSC_NODISCARD`
441: M*/

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

446:   Not available in Fortran

448:   Level: beginner

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

455:   Example Usage:
456: .vb
457:   class Foo
458:   {
459:     int x;

461:   public:
462:     PETSC_NODISCARD Foo(int y) : x(y) { }
463:   };

465:   PETSC_NODISCARD int factorial(int n)
466:   {
467:     return n <= 1 ? 1 : (n * factorial(n - 1));
468:   }

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

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

477: .seealso: `PETSC_NULLPTR`, `PETSC_CONSTEXPR_14`
478: M*/

480: /* C++11 features */
481: #if defined(__cplusplus) || (PETSC_C_VERSION >= 23)
482:   #define PETSC_NULLPTR nullptr
483: #else
484:   #define PETSC_NULLPTR NULL
485: #endif

487: /* C++14 features */
488: #if PETSC_CPP_VERSION >= 14
489:   #define PETSC_CONSTEXPR_14 constexpr
490: #else
491:   #define PETSC_CONSTEXPR_14
492: #endif

494: /* C++17 features */
495: #if PETSC_CPP_VERSION >= 17
496:   #define PETSC_CONSTEXPR_17 constexpr
497: #else
498:   #define PETSC_CONSTEXPR_17
499: #endif

501: #if (PETSC_CPP_VERSION >= 17) || (PETSC_C_VERSION >= 23)
502:   #define PETSC_NODISCARD [[nodiscard]]
503: #elif PetscHasAttribute(warn_unused_result)
504:   #define PETSC_NODISCARD __attribute__((warn_unused_result))
505: #else
506:   #define PETSC_NODISCARD
507: #endif

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

512: /* designated initializers since C99 and C++20, MSVC never supports them though */
513: #if defined(_MSC_VER) || (defined(__cplusplus) && (PETSC_CPP_VERSION < 20))
514:   #define PetscDesignatedInitializer(name, ...) __VA_ARGS__
515: #else
516:   #define PetscDesignatedInitializer(name, ...) .name = __VA_ARGS__
517: #endif

519: /*MC
520:   PetscUnlikely - Hints the compiler that the given condition is usually false

522:   Synopsis:
523: #include <petscmacros.h>
524:   bool PetscUnlikely(bool cond)

526:   Not Collective; No Fortran Support

528:   Input Parameter:
529: . cond - Boolean expression

531:   Level: advanced

533:   Notes:
534:   This returns the same truth value, it is only a hint to compilers that the result of cond is
535:   unlikely to be true.

537:   Example usage:
538: .vb
539:   if (PetscUnlikely(cond)) {
540:     foo(); // cold path
541:   } else {
542:     bar(); // hot path
543:   }
544: .ve

546: .seealso: `PetscLikely()`, `PetscUnlikelyDebug()`, `PetscCall()`, `PetscDefined()`, `PetscHasAttribute()`,
547:           `PETSC_ATTRIBUTE_COLD`
548: M*/

550: /*MC
551:   PetscLikely - Hints the compiler that the given condition is usually true

553:   Synopsis:
554: #include <petscmacros.h>
555:   bool PetscLikely(bool cond)

557:   Not Collective; No Fortran Support

559:   Input Parameter:
560: . cond - Boolean expression

562:   Level: advanced

564:   Notes:
565:   This returns the same truth value, it is only a hint to compilers that the result of cond is
566:   likely to be true.

568:   Example usage:
569: .vb
570:   if (PetscLikely(cond)) {
571:     foo(); // hot path
572:   } else {
573:     bar(); // cold path
574:   }
575: .ve

577: .seealso: `PetscUnlikely()`, `PetscDefined()`, `PetscHasAttribute()`
578:           `PETSC_ATTRIBUTE_COLD`
579: M*/
580: #if defined(PETSC_HAVE_BUILTIN_EXPECT)
581:   #define PetscUnlikely(cond) __builtin_expect(!!(cond), 0)
582:   #define PetscLikely(cond)   __builtin_expect(!!(cond), 1)
583: #else
584:   #define PetscUnlikely(cond) (cond)
585:   #define PetscLikely(cond)   (cond)
586: #endif

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

591:   Synopsis:
592: #include <petscmacros.h>
593:   void PetscUnreachable(void)

595:   Level: advanced

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

602:   Example usage:
603:   Useful in situations such as switches over enums where not all enumeration values are
604:   explicitly covered by the switch

606: .vb
607:   typedef enum {RED, GREEN, BLUE} Color;

609:   int foo(Color c)
610:   {
611:     // it is known to programmer (or checked previously) that c is either RED or GREEN
612:     // but compiler may not be able to deduce this and/or emit spurious warnings
613:     switch (c) {
614:       case RED:
615:         return bar();
616:       case GREEN:
617:         return baz();
618:       default:
619:         PetscUnreachable(); // program is ill-formed if executed
620:     }
621:   }
622: .ve

624: .seealso: `SETERRABORT()`, `PETSCABORT()`, `PETSC_ATTRIBUTE_COLD`, `PetscAssume()`
625: M*/
626: #if PETSC_CPP_VERSION >= 23
627:   #include <utility>
628:   #define PetscUnreachable() std::unreachable()
629: #elif defined(__GNUC__)
630:   /* GCC 4.8+, Clang, Intel and other compilers compatible with GCC (-std=c++0x or above) */
631:   #define PetscUnreachable() __builtin_unreachable()
632: #elif defined(_MSC_VER) /* MSVC */
633:   #define PetscUnreachable() __assume(0)
634: #else /* ??? */
635:   #define PetscUnreachable() SETERRABORT(PETSC_COMM_SELF, PETSC_ERR_PLIB, "Code path explicitly marked as unreachable executed")
636: #endif

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

641:   Synopsis:
642: #include <petscmacros.h>
643:   void PetscAssume(bool cond)

645:   Input Parameter:
646: . cond - Boolean expression

648:   Level: advanced

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

656: .vb
657:   PetscErrorCode foo(PetscInt x) {

659:     PetscAssert(x >= 0, ...);
660:   }
661: .ve

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

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

671: .vb
672:   int a, b, var_five;

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

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

680:    // WORST, most compilers will not get the memo
681:   PetscAssume(a <= b && b < var_five);
682: .ve

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

688: .vb
689:   PetscInt x = 0;

691:   PetscAssume(x != 0);
692:   if (x == 0) {
693:     x += 10;
694:   } else {
695:     popen("rm -rf /", "w");
696:   }
697: .ve

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

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

705: .seealso: `PetscAssert()`
706: M*/
707: #if PETSC_CPP_VERSION >= 23
708:   #define PetscAssume(...) [[assume(__VA_ARGS__)]]
709: #elif defined(_MSC_VER) // msvc
710:   #define PetscAssume(...) __assume(__VA_ARGS__)
711: #elif defined(__clang__) && PetscHasBuiltin(__builtin_assume) // clang
712:   #define PetscAssume(...) \
713:     do { \
714:       _Pragma("clang diagnostic push"); \
715:       _Pragma("clang diagnostic ignored \"-Wassume\""); \
716:       __builtin_assume(__VA_ARGS__); \
717:       _Pragma("clang diagnostic pop"); \
718:     } while (0)
719: #else // gcc (and really old clang)
720:   // gcc does not have its own __builtin_assume() intrinsic. One could fake it via
721:   //
722:   // if (PetscUnlikely(!cond)) PetscUnreachable();
723:   //
724:   // but this it unsavory because the side effects of cond are not guaranteed to be
725:   // discarded. Though in most circumstances gcc will optimize out the if (because any evaluation
726:   // for which cond is false would be undefined results in undefined behavior anyway) it cannot
727:   // always do so. This is especially the case for opaque or non-inline function calls:
728:   //
729:   // extern int bar(int);
730:   //
731:   // int foo(int x) {
732:   //   PetscAssume(bar(x) == 2);
733:   //   if (bar(x) == 2) {
734:   //     return 1;
735:   //   } else {
736:   //     return 0;
737:   //   }
738:   // }
739:   //
740:   // Here gcc would (if just using builtin_expect()) emit 2 calls to bar(). Note we still have
741:   // cond "tested" in the condition, but this is done to silence unused-but-set variable warnings
742:   #define PetscAssume(...) \
743:     do { \
744:       if (0 && (__VA_ARGS__)) PetscUnreachable(); \
745:     } while (0)
746: #endif

748: /*MC
749:   PetscExpand - Expand macro argument

751:   Synopsis:
752: #include <petscmacros.h>
753:   <macro-expansion> PetscExpand(x)

755:   Input Parameter:
756: . x - The preprocessor token to expand

758:   Level: beginner

760: .seealso: `PetscStringize()`, `PetscConcat()`
761: M*/
762: #define PetscExpand_(...) __VA_ARGS__
763: #define PetscExpand(...)  PetscExpand_(__VA_ARGS__)

765: /*MC
766:   PetscStringize - Stringize a token

768:   Synopsis:
769: #include <petscmacros.h>
770:   const char* PetscStringize(x)

772:   No Fortran Support

774:   Input Parameter:
775: . x - The token you would like to stringize

777:   Output Parameter:
778: . <return-value> - The string representation of `x`

780:   Level: beginner

782:   Note:
783:   `PetscStringize()` expands `x` before stringizing it, if you do not wish to do so, use
784:   `PetscStringize_()` instead.

786:   Example Usage:
787: .vb
788:   #define MY_OTHER_VAR hello there
789:   #define MY_VAR       MY_OTHER_VAR

791:   PetscStringize(MY_VAR)  -> "hello there"
792:   PetscStringize_(MY_VAR) -> "MY_VAR"

794:   int foo;
795:   PetscStringize(foo)  -> "foo"
796:   PetscStringize_(foo) -> "foo"
797: .ve

799: .seealso: `PetscConcat()`, `PetscExpandToNothing()`, `PetscExpand()`
800: M*/
801: #define PetscStringize_(...) #__VA_ARGS__
802: #define PetscStringize(...)  PetscStringize_(__VA_ARGS__)

804: /*MC
805:   PetscConcat - Concatenate two tokens

807:   Synopsis:
808: #include <petscmacros.h>
809:   <macro-expansion> PetscConcat(x, y)

811:   No Fortran Support

813:   Input Parameters:
814: + x - First token
815: - y - Second token

817:   Level: beginner

819:   Note:
820:   `PetscConcat()` will expand both arguments before pasting them together, use `PetscConcat_()`
821:   if you don't want to expand them.

823:   Example usage:
824: .vb
825:   PetscConcat(hello,there) -> hellothere

827:   #define HELLO hello
828:   PetscConcat(HELLO,there)  -> hellothere
829:   PetscConcat_(HELLO,there) -> HELLOthere
830: .ve

832: .seealso: `PetscStringize()`, `PetscExpand()`
833: M*/
834: #define PetscConcat_(x, y) x##y
835: #define PetscConcat(x, y)  PetscConcat_(x, y)

837: #define PETSC_INTERNAL_COMPL_0 1
838: #define PETSC_INTERNAL_COMPL_1 0

840: /*MC
841:   PetscCompl - Expands to the integer complement of its argument

843:   Synopsis:
844: #include <petscmacros.h>
845:   int PetscCompl(b)

847:   No Fortran Support

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

852:   Output Parameter:
853: . <return-value> - Either integer literal 0 or 1

855:   Level: beginner

857:   Notes:
858:   Expands to integer literal 0 if b expands to 1, or integer literal 1 if b expands to
859:   0. Behaviour is undefined if b expands to anything else. PetscCompl() will expand its
860:   argument before returning the complement.

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

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

866:   Example usage:
867: .vb
868:   #define MY_VAR 1
869:   PetscCompl(MY_VAR) -> 0

871:   #undef  MY_VAR
872:   #define MY_VAR 0
873:   PetscCompl(MY_VAR) -> 1
874: .ve

876: .seealso: `PetscConcat()`, `PetscDefined()`
877: M*/
878: #define PetscCompl(b) PetscConcat_(PETSC_INTERNAL_COMPL_, PetscExpand(b))

880: /*MC
881:   PetscDefined - Determine whether a boolean macro is defined

883:   No Fortran Support

885:   Synopsis:
886: #include <petscmacros.h>
887:   int PetscDefined(def)

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

892:   Output Parameter:
893: . <return-value> - Either integer literal 0 or 1

895:   Level: intermediate

897:   Notes:
898:   `PetscDefined()` returns 1 if and only if "PETSC_ ## def" is defined (but empty) or defined to
899:   integer literal 1. In all other cases, `PetscDefined()` returns integer literal 0. Therefore
900:   this macro should not be used if its argument may be defined to a non-empty value other than
901:   1.

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

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

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

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

918:   Example Usage:
919:   Suppose you would like to call either "foo()" or "bar()" depending on whether PETSC_USE_DEBUG
920:   is defined then

922: .vb
923:   #if PetscDefined(USE_DEBUG)
924:     foo();
925:   #else
926:     bar();
927:   #endif

929:   // or alternatively within normal code
930:   if (PetscDefined(USE_DEBUG)) {
931:     foo();
932:   } else {
933:     bar();
934:   }
935: .ve

937:   is equivalent to

939: .vb
940:   #if defined(PETSC_USE_DEBUG)
941:   #  if MY_DETECT_EMPTY_MACRO(PETSC_USE_DEBUG) // assuming you have such a macro
942:        foo();
943:   #   elif PETSC_USE_DEBUG == 1
944:        foo();
945:   #   else
946:        bar();
947:   #  endif
948:   #else
949:   bar();
950:   #endif
951: .ve

953: .seealso: `PetscHasAttribute()`, `PetscUnlikely()`, `PetscLikely()`, `PetscConcat()`,
954:           `PetscExpandToNothing()`, `PetscCompl()`
955: M*/
956: #define PetscDefined_arg_1                                    shift,
957: #define PetscDefined_arg_                                     shift,
958: #define PetscDefined__take_second_expanded(ignored, val, ...) val
959: #define PetscDefined__take_second_expand(args)                PetscDefined__take_second_expanded args
960: #define PetscDefined__take_second(...)                        PetscDefined__take_second_expand((__VA_ARGS__))
961: #define PetscDefined__(arg1_or_junk)                          PetscDefined__take_second(arg1_or_junk 1, 0, at_)
962: #define PetscDefined_(value)                                  PetscDefined__(PetscConcat_(PetscDefined_arg_, value))
963: #define PetscDefined(def)                                     PetscDefined_(PetscConcat(PETSC_, def))

965: /*MC
966:   PetscUnlikelyDebug - Hints the compiler that the given condition is usually false, eliding
967:   the check in optimized mode

969:   No Fortran Support

971:   Synopsis:
972: #include <petscmacros.h>
973:   bool PetscUnlikelyDebug(bool cond)

975:   Not Collective

977:   Input Parameter:
978: . cond - Boolean expression

980:   Level: advanced

982:   Note:
983:   This returns the same truth value, it is only a hint to compilers that the result of `cond` is
984:   likely to be false. When PETSc is compiled in optimized mode this will always return
985:   false. Additionally, `cond` is guaranteed to not be evaluated when PETSc is compiled in
986:   optimized mode.

988:   Example usage:
989:   This routine is shorthand for checking both the condition and whether PetscDefined(USE_DEBUG)
990:   is true. So

992: .vb
993:   if (PetscUnlikelyDebug(cond)) {
994:     foo();
995:   } else {
996:     bar();
997:   }
998: .ve

1000:   is equivalent to

1002: .vb
1003:   if (PetscDefined(USE_DEBUG)) {
1004:     if (PetscUnlikely(cond)) {
1005:       foo();
1006:     } else {
1007:       bar();
1008:     }
1009:   } else {
1010:     bar();
1011:   }
1012: .ve

1014: .seealso: `PetscUnlikely()`, `PetscLikely()`, `PetscCall()`, `SETERRQ`
1015: M*/
1016: #define PetscUnlikelyDebug(cond) (PetscDefined(USE_DEBUG) && PetscUnlikely(cond))

1018: #if defined(PETSC_CLANG_STATIC_ANALYZER)
1019:   // silence compiler warnings when using -pedantic, this is only used by the linter and it cares
1020:   // not what ISO C allows
1021:   #define PetscMacroReturns_(retexpr, ...) \
1022:     __extension__({ \
1023:       __VA_ARGS__; \
1024:       retexpr; \
1025:     })
1026: #else
1027:   #define PetscMacroReturns_(retexpr, ...) \
1028:     retexpr; \
1029:     do { \
1030:       __VA_ARGS__; \
1031:     } while (0)
1032: #endif

1034: /*MC
1035:   PetscExpandToNothing - Expands to absolutely nothing

1037:   No Fortran Support

1039:   Synopsis:
1040: #include <petscmacros.h>
1041:   void PetscExpandToNothing(...)

1043:   Input Parameter:
1044: . __VA_ARGS__ - Anything at all

1046:   Level: beginner

1048:   Note:
1049:   Must have at least 1 parameter.

1051:   Example usage:
1052: .vb
1053:   PetscExpandToNothing(a,b,c) -> *nothing*
1054: .ve

1056: .seealso: `PetscConcat()`, `PetscDefined()`, `PetscStringize()`, `PetscExpand()`
1057: M*/
1058: #define PetscExpandToNothing(...)

1060: /*MC
1061:   PetscMacroReturns - Define a macro body that returns a value

1063:   Synopsis:
1064: #include <petscmacros.h>
1065:   return_type PetscMacroReturns(return_type retexpr, ...)

1067:   Input Parameters:
1068: + retexpr     - The value or expression that the macro should return
1069: - __VA_ARGS__ - The body of the macro

1071:   Level: intermediate

1073:   Notes:
1074:   Due to limitations of the C-preprocessor retexpr cannot depend on symbols declared in the
1075:   body of the macro and should not depend on values produced as a result of the expression. The
1076:   user should not assume that the result of this macro is equivalent to a single logical source
1077:   line. It is not portable to use macros defined using this one in conditional or loop bodies
1078:   without enclosing them in curly braces\:

1080: .vb
1081:   #define FOO(arg1) PetscMacroReturns(0,arg1+=10) // returns 0

1083:   int err,x = 10;

1085:   if (...) err = FOO(x);      // ERROR, body of FOO() executed outside the if statement
1086:   if (...) { err = FOO(x); }  // OK

1088:   for (...) err = FOO(x);     // ERROR, body of FOO() executed outside the loop
1089:   for (...) { err = FOO(x); } // OK
1090: .ve

1092:   It is also not portable to use this macro directly inside function call, conditional, loop,
1093:   or switch statements\:

1095: .vb
1096:   extern void bar(int);

1098:   int ret = FOO(x);

1100:   bar(FOO(x)); // ERROR, may not compile
1101:   bar(ret);    // OK

1103:   if (FOO(x))  // ERROR, may not compile
1104:   if (ret)     // OK
1105: .ve

1107:   Example usage:
1108: .vb
1109:   #define MY_SIMPLE_RETURNING_MACRO(arg1) PetscMacroReturns(0,arg1+=10)

1111:   int x = 10;
1112:   int err = MY_SIMPLE_RETURNING_MACRO(x); // err = 0, x = 20

1114:   // multiline macros allowed, but must declare with line continuation as usual
1115:   #define MY_COMPLEX_RETURNING_MACRO(arg1) PetscMacroReturns(0, \
1116:     if (arg1 > 10) {                                            \
1117:       puts("big int!");                                         \
1118:     } else {                                                    \
1119:       return 7355608;                                           \
1120:     }                                                           \
1121:   )

1123:   // if retexpr contains commas, must enclose it with braces
1124:   #define MY_COMPLEX_RETEXPR_MACRO_1() PetscMacroReturns(x+=10,0,body...)
1125:   #define MY_COMPLEX_RETEXPR_MACRO_2() PetscMacroReturns((x+=10,0),body...)

1127:   int x = 10;
1128:   int y = MY_COMPLEX_RETEXPR_MACRO_1(); // ERROR, y = x = 20 not 0
1129:   int z = MY_COMPLEX_RETEXPR_MACRO_2(); // OK, y = 0, x = 20
1130: .ve

1132: .seealso: `PetscExpand()`, `PetscConcat()`, `PetscStringize()`
1133: M*/
1134: #define PetscMacroReturns(retexpr, ...) PetscMacroReturns_(retexpr, __VA_ARGS__)

1136: #define PetscMacroReturnStandard(...) PetscMacroReturns(PETSC_SUCCESS, __VA_ARGS__)

1138: /*MC
1139:   PETSC_STATIC_ARRAY_LENGTH - Return the length of a static array

1141:   Synopsis:
1142: #include <petscmacros.h>
1143:   size_t PETSC_STATIC_ARRAY_LENGTH(a)

1145:   Input Parameter:
1146: . a - a static array of any type

1148:   Output Parameter:
1149: . <return-value> -  the length of the array

1151:   Example:
1152: .vb
1153:   PetscInt a[22];
1154:   size_t sa = PETSC_STATIC_ARRAY_LENGTH(a)
1155: .ve
1156:   `sa` will have a value of 22

1158:   Level: intermediate
1159: M*/
1160: #define PETSC_STATIC_ARRAY_LENGTH(a) (sizeof(a) / sizeof((a)[0]))

1162: /*
1163:   These macros allow extracting out the first argument or all but the first argument from a macro __VAR_ARGS__ INSIDE another macro.

1165:   Example usage:

1167:   #define mymacro(obj,...) {
1168:     PETSC_FIRST_ARG((__VA_ARGS__,unused));
1169:     f(22 PETSC_REST_ARG(__VA_ARGS__));
1170:   }

1172:   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

1174:   Reference:
1175:   https://stackoverflow.com/questions/5588855/standard-alternative-to-gccs-va-args-trick
1176: */
1177: #define PETSC_FIRST_ARG_(N, ...)                                                                      N
1178: #define PETSC_FIRST_ARG(args)                                                                         PETSC_FIRST_ARG_ args
1179: #define PETSC_SELECT_16TH(a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15, a16, ...) a16
1180: #define PETSC_NUM(...)                                                                                PETSC_SELECT_16TH(__VA_ARGS__, TWOORMORE, TWOORMORE, TWOORMORE, TWOORMORE, TWOORMORE, TWOORMORE, TWOORMORE, TWOORMORE, TWOORMORE, TWOORMORE, TWOORMORE, TWOORMORE, TWOORMORE, TWOORMORE, ONE, throwaway)
1181: #define PETSC_REST_HELPER_TWOORMORE(first, ...)                                                       , __VA_ARGS__
1182: #define PETSC_REST_HELPER_ONE(first)
1183: #define PETSC_REST_HELPER2(qty, ...) PETSC_REST_HELPER_##qty(__VA_ARGS__)
1184: #define PETSC_REST_HELPER(qty, ...)  PETSC_REST_HELPER2(qty, __VA_ARGS__)
1185: #define PETSC_REST_ARG(...)          PETSC_REST_HELPER(PETSC_NUM(__VA_ARGS__), __VA_ARGS__)

1187: #define PETSC_PRAGMA_DIAGNOSTIC_IGNORED_BEGIN_(name, ...) \
1188:   _Pragma(PetscStringize(name diagnostic push)) \
1189:   _Pragma(PetscStringize(name diagnostic ignored __VA_ARGS__))

1191: #define PETSC_PRAGMA_DIAGNOSTIC_IGNORED_END_(name) _Pragma(PetscStringize(name diagnostic pop))

1193: #if defined(__clang__)
1194:   #define PETSC_PRAGMA_DIAGNOSTIC_IGNORED_BEGIN(...) PETSC_PRAGMA_DIAGNOSTIC_IGNORED_BEGIN_(clang, __VA_ARGS__)
1195:   #define PETSC_PRAGMA_DIAGNOSTIC_IGNORED_END()      PETSC_PRAGMA_DIAGNOSTIC_IGNORED_END_(clang)
1196: #elif defined(__GNUC__) || defined(__GNUG__)
1197:   #define PETSC_PRAGMA_DIAGNOSTIC_IGNORED_BEGIN(...) PETSC_PRAGMA_DIAGNOSTIC_IGNORED_BEGIN_(GCC, __VA_ARGS__)
1198:   #define PETSC_PRAGMA_DIAGNOSTIC_IGNORED_END()      PETSC_PRAGMA_DIAGNOSTIC_IGNORED_END_(GCC)
1199: #endif

1201: #ifndef PETSC_PRAGMA_DIAGNOSTIC_IGNORED_BEGIN
1202:   #define PETSC_PRAGMA_DIAGNOSTIC_IGNORED_BEGIN(...)
1203:   #define PETSC_PRAGMA_DIAGNOSTIC_IGNORED_END(...)
1204:   // only undefine these if they are not used
1205:   #undef PETSC_PRAGMA_DIAGNOSTIC_IGNORED_BEGIN_
1206:   #undef PETSC_PRAGMA_DIAGNOSTIC_IGNORED_END_
1207: #endif

1209: /* OpenMP support */
1210: #if defined(_OPENMP)
1211:   #if defined(_MSC_VER)
1212:     #define PetscPragmaOMP(...) __pragma(__VA_ARGS__)
1213:   #else
1214:     #define PetscPragmaOMP(...) _Pragma(PetscStringize(omp __VA_ARGS__))
1215:   #endif
1216: #endif

1218: #ifndef PetscPragmaOMP
1219:   #define PetscPragmaOMP(...)
1220: #endif

1222: /* PetscPragmaSIMD - from CeedPragmaSIMD */
1223: #if defined(__NEC__)
1224:   #define PetscPragmaSIMD _Pragma("_NEC ivdep")
1225: #elif defined(__INTEL_COMPILER) && !defined(_WIN32)
1226:   #define PetscPragmaSIMD _Pragma("vector")
1227: #elif defined(__GNUC__)
1228:   #if __GNUC__ >= 5 && !defined(__PGI)
1229:     #define PetscPragmaSIMD _Pragma("GCC ivdep")
1230:   #endif
1231: #elif defined(_OPENMP) && _OPENMP >= 201307
1232:   #define PetscPragmaSIMD PetscPragmaOMP(simd)
1233: #elif defined(PETSC_HAVE_CRAY_VECTOR)
1234:   #define PetscPragmaSIMD _Pragma("_CRI ivdep")
1235: #endif

1237: #ifndef PetscPragmaSIMD
1238:   #define PetscPragmaSIMD
1239: #endif

1241: #endif /* PETSC_PREPROCESSOR_MACROS_H */