c.h

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/*-------------------------------------------------------------------------
 *
 * c.h
 *    Fundamental C definitions.  This is included by every .c file in
 *    PostgreSQL (via either postgres.h or postgres_fe.h, as appropriate).
 *
 *    Note that the definitions here are not intended to be exposed to clients
 *    of the frontend interface libraries --- so we don't worry much about
 *    polluting the namespace with lots of stuff...
 *
 *
 * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/c.h
 *
 *-------------------------------------------------------------------------
 */
/*
 *----------------------------------------------------------------
 *   TABLE OF CONTENTS
 *
 *      When adding stuff to this file, please try to put stuff
 *      into the relevant section, or add new sections as appropriate.
 *
 *    section   description
 *    -------   ------------------------------------------------
 *      0)      pg_config.h and standard system headers
 *      1)      hacks to cope with non-ANSI C compilers
 *      2)      bool, true, false, TRUE, FALSE, NULL
 *      3)      standard system types
 *      4)      IsValid macros for system types
 *      5)      offsetof, lengthof, endof, alignment
 *      6)      assertions
 *      7)      widely useful macros
 *      8)      random stuff
 *      9)      system-specific hacks
 *
 * NOTE: since this file is included by both frontend and backend modules, it's
 * almost certainly wrong to put an "extern" declaration here.  typedefs and
 * macros are the kind of thing that might go here.
 *
 *----------------------------------------------------------------
 */
#ifndef C_H
#define C_H

#include "postgres_ext.h"

/* Must undef pg_config_ext.h symbols before including pg_config.h */
#undef PG_INT64_TYPE

#include "pg_config.h"
#include "pg_config_manual.h"   /* must be after pg_config.h */

/*
 * We always rely on the WIN32 macro being set by our build system,
 * but _WIN32 is the compiler pre-defined macro. So make sure we define
 * WIN32 whenever _WIN32 is set, to facilitate standalone building.
 */
#if defined(_WIN32) && !defined(WIN32)
#define WIN32
#endif

#if !defined(WIN32) && !defined(__CYGWIN__) /* win32 includes further down */
#include "pg_config_os.h"       /* must be before any system header files */
#endif

#if _MSC_VER >= 1400 || defined(HAVE_CRTDEFS_H)
#define errcode __msvc_errcode
#include <crtdefs.h>
#undef errcode
#endif

/*
 * We have to include stdlib.h here because it defines many of these macros
 * on some platforms, and we only want our definitions used if stdlib.h doesn't
 * have its own.  The same goes for stddef and stdarg if present.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stddef.h>
#include <stdarg.h>
#ifdef HAVE_STRINGS_H
#include <strings.h>
#endif
#ifdef HAVE_STDINT_H
#include <stdint.h>
#endif
#include <sys/types.h>

#include <errno.h>
#if defined(WIN32) || defined(__CYGWIN__)
#include <fcntl.h>              /* ensure O_BINARY is available */
#endif

#if defined(WIN32) || defined(__CYGWIN__)
/* We have to redefine some system functions after they are included above. */
#include "pg_config_os.h"
#endif

/*
 * Force disable inlining if PG_FORCE_DISABLE_INLINE is defined. This is used
 * to work around compiler bugs and might also be useful for investigatory
 * purposes by defining the symbol in the platform's header..
 *
 * This is done early (in slightly the wrong section) as functionality later
 * in this file might want to rely on inline functions.
 */
#ifdef PG_FORCE_DISABLE_INLINE
#undef inline
#define inline
#endif

/* Must be before gettext() games below */
#include <locale.h>

#define _(x) gettext(x)

#ifdef ENABLE_NLS
#include <libintl.h>
#else
#define gettext(x) (x)
#define dgettext(d,x) (x)
#define ngettext(s,p,n) ((n) == 1 ? (s) : (p))
#define dngettext(d,s,p,n) ((n) == 1 ? (s) : (p))
#endif

/*
 *  Use this to mark string constants as needing translation at some later
 *  time, rather than immediately.  This is useful for cases where you need
 *  access to the original string and translated string, and for cases where
 *  immediate translation is not possible, like when initializing global
 *  variables.
 *      http://www.gnu.org/software/autoconf/manual/gettext/Special-cases.html
 */
#define gettext_noop(x) (x)


/* ----------------------------------------------------------------
 *              Section 1: hacks to cope with non-ANSI C compilers
 *
 * type prefixes (const, signed, volatile, inline) are handled in pg_config.h.
 * ----------------------------------------------------------------
 */

/*
 * CppAsString
 *      Convert the argument to a string, using the C preprocessor.
 * CppAsString2
 *      Convert the argument to a string, after one round of macro expansion.
 * CppConcat
 *      Concatenate two arguments together, using the C preprocessor.
 *
 * Note: There used to be support here for pre-ANSI C compilers that didn't
 * support # and ##.  Nowadays, these macros are just for clarity and/or
 * backward compatibility with existing PostgreSQL code.
 */
#define CppAsString(identifier) #identifier
#define CppAsString2(x)         CppAsString(x)
#define CppConcat(x, y)         x##y

/*
 * dummyret is used to set return values in macros that use ?: to make
 * assignments.  gcc wants these to be void, other compilers like char
 */
#ifdef __GNUC__                 /* GNU cc */
#define dummyret    void
#else
#define dummyret    char
#endif

/* Which __func__ symbol do we have, if any? */
#ifdef HAVE_FUNCNAME__FUNC
#define PG_FUNCNAME_MACRO   __func__
#else
#ifdef HAVE_FUNCNAME__FUNCTION
#define PG_FUNCNAME_MACRO   __FUNCTION__
#else
#define PG_FUNCNAME_MACRO   NULL
#endif
#endif

/* ----------------------------------------------------------------
 *              Section 2:  bool, true, false, TRUE, FALSE, NULL
 * ----------------------------------------------------------------
 */

/*
 * bool
 *      Boolean value, either true or false.
 *
 * XXX for C++ compilers, we assume the compiler has a compatible
 * built-in definition of bool.
 */

#ifndef __cplusplus

#ifndef bool
typedef char bool;
#endif

#ifndef true
#define true    ((bool) 1)
#endif

#ifndef false
#define false   ((bool) 0)
#endif
#endif                          /* not C++ */

typedef bool *BoolPtr;

#ifndef TRUE
#define TRUE    1
#endif

#ifndef FALSE
#define FALSE   0
#endif

/*
 * NULL
 *      Null pointer.
 */
#ifndef NULL
#define NULL    ((void *) 0)
#endif


/* ----------------------------------------------------------------
 *              Section 3:  standard system types
 * ----------------------------------------------------------------
 */

/*
 * Pointer
 *      Variable holding address of any memory resident object.
 *
 *      XXX Pointer arithmetic is done with this, so it can't be void *
 *      under "true" ANSI compilers.
 */
typedef char *Pointer;

/*
 * intN
 *      Signed integer, EXACTLY N BITS IN SIZE,
 *      used for numerical computations and the
 *      frontend/backend protocol.
 */
#ifndef HAVE_INT8
typedef signed char int8;       /* == 8 bits */
typedef signed short int16;     /* == 16 bits */
typedef signed int int32;       /* == 32 bits */
#endif                          /* not HAVE_INT8 */

/*
 * uintN
 *      Unsigned integer, EXACTLY N BITS IN SIZE,
 *      used for numerical computations and the
 *      frontend/backend protocol.
 */
#ifndef HAVE_UINT8
typedef unsigned char uint8;    /* == 8 bits */
typedef unsigned short uint16;  /* == 16 bits */
typedef unsigned int uint32;    /* == 32 bits */
#endif                          /* not HAVE_UINT8 */

/*
 * bitsN
 *      Unit of bitwise operation, AT LEAST N BITS IN SIZE.
 */
typedef uint8 bits8;            /* >= 8 bits */
typedef uint16 bits16;          /* >= 16 bits */
typedef uint32 bits32;          /* >= 32 bits */

/*
 * 64-bit integers
 */
#ifdef HAVE_LONG_INT_64
/* Plain "long int" fits, use it */

#ifndef HAVE_INT64
typedef long int int64;
#endif
#ifndef HAVE_UINT64
typedef unsigned long int uint64;
#endif
#elif defined(HAVE_LONG_LONG_INT_64)
/* We have working support for "long long int", use that */

#ifndef HAVE_INT64
typedef long long int int64;
#endif
#ifndef HAVE_UINT64
typedef unsigned long long int uint64;
#endif
#else
/* neither HAVE_LONG_INT_64 nor HAVE_LONG_LONG_INT_64 */
#error must have a working 64-bit integer datatype
#endif

/* Decide if we need to decorate 64-bit constants */
#ifdef HAVE_LL_CONSTANTS
#define INT64CONST(x)  ((int64) x##LL)
#define UINT64CONST(x) ((uint64) x##ULL)
#else
#define INT64CONST(x)  ((int64) x)
#define UINT64CONST(x) ((uint64) x)
#endif

/* snprintf format strings to use for 64-bit integers */
#define INT64_FORMAT "%" INT64_MODIFIER "d"
#define UINT64_FORMAT "%" INT64_MODIFIER "u"

/*
 * 128-bit signed and unsigned integers
 *      There currently is only a limited support for the type. E.g. 128bit
 *      literals and snprintf are not supported; but math is.
 */
#if defined(PG_INT128_TYPE)
#define HAVE_INT128
typedef PG_INT128_TYPE int128;
typedef unsigned PG_INT128_TYPE uint128;
#endif

/*
 * stdint.h limits aren't guaranteed to be present and aren't guaranteed to
 * have compatible types with our fixed width types. So just define our own.
 */
#define PG_INT8_MIN     (-0x7F-1)
#define PG_INT8_MAX     (0x7F)
#define PG_UINT8_MAX    (0xFF)
#define PG_INT16_MIN    (-0x7FFF-1)
#define PG_INT16_MAX    (0x7FFF)
#define PG_UINT16_MAX   (0xFFFF)
#define PG_INT32_MIN    (-0x7FFFFFFF-1)
#define PG_INT32_MAX    (0x7FFFFFFF)
#define PG_UINT32_MAX   (0xFFFFFFFF)
#define PG_INT64_MIN    (-INT64CONST(0x7FFFFFFFFFFFFFFF) - 1)
#define PG_INT64_MAX    INT64CONST(0x7FFFFFFFFFFFFFFF)
#define PG_UINT64_MAX   UINT64CONST(0xFFFFFFFFFFFFFFFF)

/*
 * We now always use int64 timestamps, but keep this symbol defined for the
 * benefit of external code that might test it.
 */
#define HAVE_INT64_TIMESTAMP

/*
 * Size
 *      Size of any memory resident object, as returned by sizeof.
 */
typedef size_t Size;

/*
 * Index
 *      Index into any memory resident array.
 *
 * Note:
 *      Indices are non negative.
 */
typedef unsigned int Index;

/*
 * Offset
 *      Offset into any memory resident array.
 *
 * Note:
 *      This differs from an Index in that an Index is always
 *      non negative, whereas Offset may be negative.
 */
typedef signed int Offset;

/*
 * Common Postgres datatype names (as used in the catalogs)
 */
typedef float float4;
typedef double float8;

/*
 * Oid, RegProcedure, TransactionId, SubTransactionId, MultiXactId,
 * CommandId
 */

/* typedef Oid is in postgres_ext.h */

/*
 * regproc is the type name used in the include/catalog headers, but
 * RegProcedure is the preferred name in C code.
 */
typedef Oid regproc;
typedef regproc RegProcedure;

typedef uint32 TransactionId;

typedef uint32 LocalTransactionId;

typedef uint32 SubTransactionId;

#define InvalidSubTransactionId     ((SubTransactionId) 0)
#define TopSubTransactionId         ((SubTransactionId) 1)

/* MultiXactId must be equivalent to TransactionId, to fit in t_xmax */
typedef TransactionId MultiXactId;

typedef uint32 MultiXactOffset;

typedef uint32 CommandId;

#define FirstCommandId  ((CommandId) 0)
#define InvalidCommandId    (~(CommandId)0)

/*
 * Array indexing support
 */
#define MAXDIM 6
typedef struct
{
    int         indx[MAXDIM];
}           IntArray;

/* ----------------
 *      Variable-length datatypes all share the 'struct varlena' header.
 *
 * NOTE: for TOASTable types, this is an oversimplification, since the value
 * may be compressed or moved out-of-line.  However datatype-specific routines
 * are mostly content to deal with de-TOASTed values only, and of course
 * client-side routines should never see a TOASTed value.  But even in a
 * de-TOASTed value, beware of touching vl_len_ directly, as its
 * representation is no longer convenient.  It's recommended that code always
 * use macros VARDATA_ANY, VARSIZE_ANY, VARSIZE_ANY_EXHDR, VARDATA, VARSIZE,
 * and SET_VARSIZE instead of relying on direct mentions of the struct fields.
 * See postgres.h for details of the TOASTed form.
 * ----------------
 */
struct varlena
{
    char        vl_len_[4];     /* Do not touch this field directly! */
    char        vl_dat[FLEXIBLE_ARRAY_MEMBER];  /* Data content is here */
};

#define VARHDRSZ        ((int32) sizeof(int32))

/*
 * These widely-used datatypes are just a varlena header and the data bytes.
 * There is no terminating null or anything like that --- the data length is
 * always VARSIZE_ANY_EXHDR(ptr).
 */
typedef struct varlena bytea;
typedef struct varlena text;
typedef struct varlena BpChar;  /* blank-padded char, ie SQL char(n) */
typedef struct varlena VarChar; /* var-length char, ie SQL varchar(n) */

/*
 * Specialized array types.  These are physically laid out just the same
 * as regular arrays (so that the regular array subscripting code works
 * with them).  They exist as distinct types mostly for historical reasons:
 * they have nonstandard I/O behavior which we don't want to change for fear
 * of breaking applications that look at the system catalogs.  There is also
 * an implementation issue for oidvector: it's part of the primary key for
 * pg_proc, and we can't use the normal btree array support routines for that
 * without circularity.
 */
typedef struct
{
    int32       vl_len_;        /* these fields must match ArrayType! */
    int         ndim;           /* always 1 for int2vector */
    int32       dataoffset;     /* always 0 for int2vector */
    Oid         elemtype;
    int         dim1;
    int         lbound1;
    int16       values[FLEXIBLE_ARRAY_MEMBER];
} int2vector;

typedef struct
{
    int32       vl_len_;        /* these fields must match ArrayType! */
    int         ndim;           /* always 1 for oidvector */
    int32       dataoffset;     /* always 0 for oidvector */
    Oid         elemtype;
    int         dim1;
    int         lbound1;
    Oid         values[FLEXIBLE_ARRAY_MEMBER];
} oidvector;

/*
 * Representation of a Name: effectively just a C string, but null-padded to
 * exactly NAMEDATALEN bytes.  The use of a struct is historical.
 */
typedef struct nameData
{
    char        data[NAMEDATALEN];
} NameData;
typedef NameData *Name;

#define NameStr(name)   ((name).data)

/*
 * Support macros for escaping strings.  escape_backslash should be TRUE
 * if generating a non-standard-conforming string.  Prefixing a string
 * with ESCAPE_STRING_SYNTAX guarantees it is non-standard-conforming.
 * Beware of multiple evaluation of the "ch" argument!
 */
#define SQL_STR_DOUBLE(ch, escape_backslash)    \
    ((ch) == '\'' || ((ch) == '\\' && (escape_backslash)))

#define ESCAPE_STRING_SYNTAX    'E'

/* ----------------------------------------------------------------
 *              Section 4:  IsValid macros for system types
 * ----------------------------------------------------------------
 */
/*
 * BoolIsValid
 *      True iff bool is valid.
 */
#define BoolIsValid(boolean)    ((boolean) == false || (boolean) == true)

/*
 * PointerIsValid
 *      True iff pointer is valid.
 */
#define PointerIsValid(pointer) ((const void*)(pointer) != NULL)

/*
 * PointerIsAligned
 *      True iff pointer is properly aligned to point to the given type.
 */
#define PointerIsAligned(pointer, type) \
        (((uintptr_t)(pointer) % (sizeof (type))) == 0)

#define OffsetToPointer(base, offset) \
        ((void *)((char *) base + offset))

#define OidIsValid(objectId)  ((bool) ((objectId) != InvalidOid))

#define RegProcedureIsValid(p)  OidIsValid(p)


/* ----------------------------------------------------------------
 *              Section 5:  offsetof, lengthof, endof, alignment
 * ----------------------------------------------------------------
 */
/*
 * offsetof
 *      Offset of a structure/union field within that structure/union.
 *
 *      XXX This is supposed to be part of stddef.h, but isn't on
 *      some systems (like SunOS 4).
 */
#ifndef offsetof
#define offsetof(type, field)   ((long) &((type *)0)->field)
#endif                          /* offsetof */

/*
 * lengthof
 *      Number of elements in an array.
 */
#define lengthof(array) (sizeof (array) / sizeof ((array)[0]))

/*
 * endof
 *      Address of the element one past the last in an array.
 */
#define endof(array)    (&(array)[lengthof(array)])

/* ----------------
 * Alignment macros: align a length or address appropriately for a given type.
 * The fooALIGN() macros round up to a multiple of the required alignment,
 * while the fooALIGN_DOWN() macros round down.  The latter are more useful
 * for problems like "how many X-sized structures will fit in a page?".
 *
 * NOTE: TYPEALIGN[_DOWN] will not work if ALIGNVAL is not a power of 2.
 * That case seems extremely unlikely to be needed in practice, however.
 * ----------------
 */

#define TYPEALIGN(ALIGNVAL,LEN)  \
    (((uintptr_t) (LEN) + ((ALIGNVAL) - 1)) & ~((uintptr_t) ((ALIGNVAL) - 1)))

#define SHORTALIGN(LEN)         TYPEALIGN(ALIGNOF_SHORT, (LEN))
#define INTALIGN(LEN)           TYPEALIGN(ALIGNOF_INT, (LEN))
#define LONGALIGN(LEN)          TYPEALIGN(ALIGNOF_LONG, (LEN))
#define DOUBLEALIGN(LEN)        TYPEALIGN(ALIGNOF_DOUBLE, (LEN))
#define MAXALIGN(LEN)           TYPEALIGN(MAXIMUM_ALIGNOF, (LEN))
/* MAXALIGN covers only built-in types, not buffers */
#define BUFFERALIGN(LEN)        TYPEALIGN(ALIGNOF_BUFFER, (LEN))
#define CACHELINEALIGN(LEN)     TYPEALIGN(PG_CACHE_LINE_SIZE, (LEN))

#define TYPEALIGN_DOWN(ALIGNVAL,LEN)  \
    (((uintptr_t) (LEN)) & ~((uintptr_t) ((ALIGNVAL) - 1)))

#define SHORTALIGN_DOWN(LEN)    TYPEALIGN_DOWN(ALIGNOF_SHORT, (LEN))
#define INTALIGN_DOWN(LEN)      TYPEALIGN_DOWN(ALIGNOF_INT, (LEN))
#define LONGALIGN_DOWN(LEN)     TYPEALIGN_DOWN(ALIGNOF_LONG, (LEN))
#define DOUBLEALIGN_DOWN(LEN)   TYPEALIGN_DOWN(ALIGNOF_DOUBLE, (LEN))
#define MAXALIGN_DOWN(LEN)      TYPEALIGN_DOWN(MAXIMUM_ALIGNOF, (LEN))
#define BUFFERALIGN_DOWN(LEN)   TYPEALIGN_DOWN(ALIGNOF_BUFFER, (LEN))

/*
 * The above macros will not work with types wider than uintptr_t, like with
 * uint64 on 32-bit platforms.  That's not problem for the usual use where a
 * pointer or a length is aligned, but for the odd case that you need to
 * align something (potentially) wider, use TYPEALIGN64.
 */
#define TYPEALIGN64(ALIGNVAL,LEN)  \
    (((uint64) (LEN) + ((ALIGNVAL) - 1)) & ~((uint64) ((ALIGNVAL) - 1)))

/* we don't currently need wider versions of the other ALIGN macros */
#define MAXALIGN64(LEN)         TYPEALIGN64(MAXIMUM_ALIGNOF, (LEN))

/* ----------------
 * Attribute macros
 *
 * GCC: https://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html
 * GCC: https://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html
 * Sunpro: https://docs.oracle.com/cd/E18659_01/html/821-1384/gjzke.html
 * XLC: http://www-01.ibm.com/support/knowledgecenter/SSGH2K_11.1.0/com.ibm.xlc111.aix.doc/language_ref/function_attributes.html
 * XLC: http://www-01.ibm.com/support/knowledgecenter/SSGH2K_11.1.0/com.ibm.xlc111.aix.doc/language_ref/type_attrib.html
 * ----------------
 */

/* only GCC supports the unused attribute */
#ifdef __GNUC__
#define pg_attribute_unused() __attribute__((unused))
#else
#define pg_attribute_unused()
#endif

/* GCC and XLC support format attributes */
#if defined(__GNUC__) || defined(__IBMC__)
#define pg_attribute_format_arg(a) __attribute__((format_arg(a)))
#define pg_attribute_printf(f,a) __attribute__((format(PG_PRINTF_ATTRIBUTE, f, a)))
#else
#define pg_attribute_format_arg(a)
#define pg_attribute_printf(f,a)
#endif

/* GCC, Sunpro and XLC support aligned, packed and noreturn */
#if defined(__GNUC__) || defined(__SUNPRO_C) || defined(__IBMC__)
#define pg_attribute_aligned(a) __attribute__((aligned(a)))
#define pg_attribute_noreturn() __attribute__((noreturn))
#define pg_attribute_packed() __attribute__((packed))
#define HAVE_PG_ATTRIBUTE_NORETURN 1
#else
/*
 * NB: aligned and packed are not given default definitions because they
 * affect code functionality; they *must* be implemented by the compiler
 * if they are to be used.
 */
#define pg_attribute_noreturn()
#endif

/* ----------------------------------------------------------------
 *              Section 6:  assertions
 * ----------------------------------------------------------------
 */

/*
 * USE_ASSERT_CHECKING, if defined, turns on all the assertions.
 * - plai  9/5/90
 *
 * It should _NOT_ be defined in releases or in benchmark copies
 */

/*
 * Assert() can be used in both frontend and backend code. In frontend code it
 * just calls the standard assert, if it's available. If use of assertions is
 * not configured, it does nothing.
 */
#ifndef USE_ASSERT_CHECKING

#define Assert(condition)   ((void)true)
#define AssertMacro(condition)  ((void)true)
#define AssertArg(condition)    ((void)true)
#define AssertState(condition)  ((void)true)
#define AssertPointerAlignment(ptr, bndr)   ((void)true)
#define Trap(condition, errorType)  ((void)true)
#define TrapMacro(condition, errorType) (true)

#elif defined(FRONTEND)

#include <assert.h>
#define Assert(p) assert(p)
#define AssertMacro(p)  ((void) assert(p))
#define AssertArg(condition) assert(condition)
#define AssertState(condition) assert(condition)
#define AssertPointerAlignment(ptr, bndr)   ((void)true)
#else                           /* USE_ASSERT_CHECKING && !FRONTEND */

/*
 * Trap
 *      Generates an exception if the given condition is true.
 */
#define Trap(condition, errorType) \
    do { \
        if (condition) \
            ExceptionalCondition(CppAsString(condition), (errorType), \
                                 __FILE__, __LINE__); \
    } while (0)

/*
 *  TrapMacro is the same as Trap but it's intended for use in macros:
 *
 *      #define foo(x) (AssertMacro(x != 0), bar(x))
 *
 *  Isn't CPP fun?
 */
#define TrapMacro(condition, errorType) \
    ((bool) (! (condition) || \
             (ExceptionalCondition(CppAsString(condition), (errorType), \
                                   __FILE__, __LINE__), 0)))

#define Assert(condition) \
        Trap(!(condition), "FailedAssertion")

#define AssertMacro(condition) \
        ((void) TrapMacro(!(condition), "FailedAssertion"))

#define AssertArg(condition) \
        Trap(!(condition), "BadArgument")

#define AssertState(condition) \
        Trap(!(condition), "BadState")

/*
 * Check that `ptr' is `bndr' aligned.
 */
#define AssertPointerAlignment(ptr, bndr) \
    Trap(TYPEALIGN(bndr, (uintptr_t)(ptr)) != (uintptr_t)(ptr), \
         "UnalignedPointer")

#endif                          /* USE_ASSERT_CHECKING && !FRONTEND */

/*
 * Macros to support compile-time assertion checks.
 *
 * If the "condition" (a compile-time-constant expression) evaluates to false,
 * throw a compile error using the "errmessage" (a string literal).
 *
 * gcc 4.6 and up supports _Static_assert(), but there are bizarre syntactic
 * placement restrictions.  These macros make it safe to use as a statement
 * or in an expression, respectively.
 *
 * Otherwise we fall back on a kluge that assumes the compiler will complain
 * about a negative width for a struct bit-field.  This will not include a
 * helpful error message, but it beats not getting an error at all.
 */
#ifdef HAVE__STATIC_ASSERT
#define StaticAssertStmt(condition, errmessage) \
    do { _Static_assert(condition, errmessage); } while(0)
#define StaticAssertExpr(condition, errmessage) \
    ({ StaticAssertStmt(condition, errmessage); true; })
#else                           /* !HAVE__STATIC_ASSERT */
#define StaticAssertStmt(condition, errmessage) \
    ((void) sizeof(struct { int static_assert_failure : (condition) ? 1 : -1; }))
#define StaticAssertExpr(condition, errmessage) \
    StaticAssertStmt(condition, errmessage)
#endif                          /* HAVE__STATIC_ASSERT */


/*
 * Compile-time checks that a variable (or expression) has the specified type.
 *
 * AssertVariableIsOfType() can be used as a statement.
 * AssertVariableIsOfTypeMacro() is intended for use in macros, eg
 *      #define foo(x) (AssertVariableIsOfTypeMacro(x, int), bar(x))
 *
 * If we don't have __builtin_types_compatible_p, we can still assert that
 * the types have the same size.  This is far from ideal (especially on 32-bit
 * platforms) but it provides at least some coverage.
 */
#ifdef HAVE__BUILTIN_TYPES_COMPATIBLE_P
#define AssertVariableIsOfType(varname, typename) \
    StaticAssertStmt(__builtin_types_compatible_p(__typeof__(varname), typename), \
    CppAsString(varname) " does not have type " CppAsString(typename))
#define AssertVariableIsOfTypeMacro(varname, typename) \
    ((void) StaticAssertExpr(__builtin_types_compatible_p(__typeof__(varname), typename), \
     CppAsString(varname) " does not have type " CppAsString(typename)))
#else                           /* !HAVE__BUILTIN_TYPES_COMPATIBLE_P */
#define AssertVariableIsOfType(varname, typename) \
    StaticAssertStmt(sizeof(varname) == sizeof(typename), \
    CppAsString(varname) " does not have type " CppAsString(typename))
#define AssertVariableIsOfTypeMacro(varname, typename) \
    ((void) StaticAssertExpr(sizeof(varname) == sizeof(typename),       \
     CppAsString(varname) " does not have type " CppAsString(typename)))
#endif                          /* HAVE__BUILTIN_TYPES_COMPATIBLE_P */


/* ----------------------------------------------------------------
 *              Section 7:  widely useful macros
 * ----------------------------------------------------------------
 */
/*
 * Max
 *      Return the maximum of two numbers.
 */
#define Max(x, y)       ((x) > (y) ? (x) : (y))

/*
 * Min
 *      Return the minimum of two numbers.
 */
#define Min(x, y)       ((x) < (y) ? (x) : (y))

/*
 * Abs
 *      Return the absolute value of the argument.
 */
#define Abs(x)          ((x) >= 0 ? (x) : -(x))

/*
 * StrNCpy
 *  Like standard library function strncpy(), except that result string
 *  is guaranteed to be null-terminated --- that is, at most N-1 bytes
 *  of the source string will be kept.
 *  Also, the macro returns no result (too hard to do that without
 *  evaluating the arguments multiple times, which seems worse).
 *
 *  BTW: when you need to copy a non-null-terminated string (like a text
 *  datum) and add a null, do not do it with StrNCpy(..., len+1).  That
 *  might seem to work, but it fetches one byte more than there is in the
 *  text object.  One fine day you'll have a SIGSEGV because there isn't
 *  another byte before the end of memory.  Don't laugh, we've had real
 *  live bug reports from real live users over exactly this mistake.
 *  Do it honestly with "memcpy(dst,src,len); dst[len] = '\0';", instead.
 */
#define StrNCpy(dst,src,len) \
    do \
    { \
        char * _dst = (dst); \
        Size _len = (len); \
\
        if (_len > 0) \
        { \
            strncpy(_dst, (src), _len); \
            _dst[_len-1] = '\0'; \
        } \
    } while (0)


/* Get a bit mask of the bits set in non-long aligned addresses */
#define LONG_ALIGN_MASK (sizeof(long) - 1)

/*
 * MemSet
 *  Exactly the same as standard library function memset(), but considerably
 *  faster for zeroing small word-aligned structures (such as parsetree nodes).
 *  This has to be a macro because the main point is to avoid function-call
 *  overhead.   However, we have also found that the loop is faster than
 *  native libc memset() on some platforms, even those with assembler
 *  memset() functions.  More research needs to be done, perhaps with
 *  MEMSET_LOOP_LIMIT tests in configure.
 */
#define MemSet(start, val, len) \
    do \
    { \
        /* must be void* because we don't know if it is integer aligned yet */ \
        void   *_vstart = (void *) (start); \
        int     _val = (val); \
        Size    _len = (len); \
\
        if ((((uintptr_t) _vstart) & LONG_ALIGN_MASK) == 0 && \
            (_len & LONG_ALIGN_MASK) == 0 && \
            _val == 0 && \
            _len <= MEMSET_LOOP_LIMIT && \
            /* \
             *  If MEMSET_LOOP_LIMIT == 0, optimizer should find \
             *  the whole "if" false at compile time. \
             */ \
            MEMSET_LOOP_LIMIT != 0) \
        { \
            long *_start = (long *) _vstart; \
            long *_stop = (long *) ((char *) _start + _len); \
            while (_start < _stop) \
                *_start++ = 0; \
        } \
        else \
            memset(_vstart, _val, _len); \
    } while (0)

/*
 * MemSetAligned is the same as MemSet except it omits the test to see if
 * "start" is word-aligned.  This is okay to use if the caller knows a-priori
 * that the pointer is suitably aligned (typically, because he just got it
 * from palloc(), which always delivers a max-aligned pointer).
 */
#define MemSetAligned(start, val, len) \
    do \
    { \
        long   *_start = (long *) (start); \
        int     _val = (val); \
        Size    _len = (len); \
\
        if ((_len & LONG_ALIGN_MASK) == 0 && \
            _val == 0 && \
            _len <= MEMSET_LOOP_LIMIT && \
            MEMSET_LOOP_LIMIT != 0) \
        { \
            long *_stop = (long *) ((char *) _start + _len); \
            while (_start < _stop) \
                *_start++ = 0; \
        } \
        else \
            memset(_start, _val, _len); \
    } while (0)


/*
 * MemSetTest/MemSetLoop are a variant version that allow all the tests in
 * MemSet to be done at compile time in cases where "val" and "len" are
 * constants *and* we know the "start" pointer must be word-aligned.
 * If MemSetTest succeeds, then it is okay to use MemSetLoop, otherwise use
 * MemSetAligned.  Beware of multiple evaluations of the arguments when using
 * this approach.
 */
#define MemSetTest(val, len) \
    ( ((len) & LONG_ALIGN_MASK) == 0 && \
    (len) <= MEMSET_LOOP_LIMIT && \
    MEMSET_LOOP_LIMIT != 0 && \
    (val) == 0 )

#define MemSetLoop(start, val, len) \
    do \
    { \
        long * _start = (long *) (start); \
        long * _stop = (long *) ((char *) _start + (Size) (len)); \
    \
        while (_start < _stop) \
            *_start++ = 0; \
    } while (0)


/*
 * Mark a point as unreachable in a portable fashion.  This should preferably
 * be something that the compiler understands, to aid code generation.
 * In assert-enabled builds, we prefer abort() for debugging reasons.
 */
#if defined(HAVE__BUILTIN_UNREACHABLE) && !defined(USE_ASSERT_CHECKING)
#define pg_unreachable() __builtin_unreachable()
#elif defined(_MSC_VER) && !defined(USE_ASSERT_CHECKING)
#define pg_unreachable() __assume(0)
#else
#define pg_unreachable() abort()
#endif


/*
 * Hints to the compiler about the likelihood of a branch. Both likely() and
 * unlikely() return the boolean value of the contained expression.
 *
 * These should only be used sparingly, in very hot code paths. It's very easy
 * to mis-estimate likelihoods.
 */
#if __GNUC__ >= 3
#define likely(x)   __builtin_expect((x) != 0, 1)
#define unlikely(x) __builtin_expect((x) != 0, 0)
#else
#define likely(x)   ((x) != 0)
#define unlikely(x) ((x) != 0)
#endif


/* ----------------------------------------------------------------
 *              Section 8:  random stuff
 * ----------------------------------------------------------------
 */

/* msb for char */
#define HIGHBIT                 (0x80)
#define IS_HIGHBIT_SET(ch)      ((unsigned char)(ch) & HIGHBIT)

#define STATUS_OK               (0)
#define STATUS_ERROR            (-1)
#define STATUS_EOF              (-2)
#define STATUS_FOUND            (1)
#define STATUS_WAITING          (2)


/*
 * Append PG_USED_FOR_ASSERTS_ONLY to definitions of variables that are only
 * used in assert-enabled builds, to avoid compiler warnings about unused
 * variables in assert-disabled builds.
 */
#ifdef USE_ASSERT_CHECKING
#define PG_USED_FOR_ASSERTS_ONLY
#else
#define PG_USED_FOR_ASSERTS_ONLY pg_attribute_unused()
#endif


/* gettext domain name mangling */

/*
 * To better support parallel installations of major PostgreSQL
 * versions as well as parallel installations of major library soname
 * versions, we mangle the gettext domain name by appending those
 * version numbers.  The coding rule ought to be that wherever the
 * domain name is mentioned as a literal, it must be wrapped into
 * PG_TEXTDOMAIN().  The macros below do not work on non-literals; but
 * that is somewhat intentional because it avoids having to worry
 * about multiple states of premangling and postmangling as the values
 * are being passed around.
 *
 * Make sure this matches the installation rules in nls-global.mk.
 */
#ifdef SO_MAJOR_VERSION
#define PG_TEXTDOMAIN(domain) (domain CppAsString2(SO_MAJOR_VERSION) "-" PG_MAJORVERSION)
#else
#define PG_TEXTDOMAIN(domain) (domain "-" PG_MAJORVERSION)
#endif


/* ----------------------------------------------------------------
 *              Section 9: system-specific hacks
 *
 *      This should be limited to things that absolutely have to be
 *      included in every source file.  The port-specific header file
 *      is usually a better place for this sort of thing.
 * ----------------------------------------------------------------
 */

/*
 *  NOTE:  this is also used for opening text files.
 *  WIN32 treats Control-Z as EOF in files opened in text mode.
 *  Therefore, we open files in binary mode on Win32 so we can read
 *  literal control-Z.  The other affect is that we see CRLF, but
 *  that is OK because we can already handle those cleanly.
 */
#if defined(WIN32) || defined(__CYGWIN__)
#define PG_BINARY   O_BINARY
#define PG_BINARY_A "ab"
#define PG_BINARY_R "rb"
#define PG_BINARY_W "wb"
#else
#define PG_BINARY   0
#define PG_BINARY_A "a"
#define PG_BINARY_R "r"
#define PG_BINARY_W "w"
#endif

/*
 * Provide prototypes for routines not present in a particular machine's
 * standard C library.
 */

#if !HAVE_DECL_SNPRINTF
extern int  snprintf(char *str, size_t count, const char *fmt,...) pg_attribute_printf(3, 4);
#endif

#if !HAVE_DECL_VSNPRINTF
extern int  vsnprintf(char *str, size_t count, const char *fmt, va_list args);
#endif

#if !defined(HAVE_MEMMOVE) && !defined(memmove)
#define memmove(d, s, c)        bcopy(s, d, c)
#endif

/* no special DLL markers on most ports */
#ifndef PGDLLIMPORT
#define PGDLLIMPORT
#endif
#ifndef PGDLLEXPORT
#define PGDLLEXPORT
#endif

/*
 * The following is used as the arg list for signal handlers.  Any ports
 * that take something other than an int argument should override this in
 * their pg_config_os.h file.  Note that variable names are required
 * because it is used in both the prototypes as well as the definitions.
 * Note also the long name.  We expect that this won't collide with
 * other names causing compiler warnings.
 */

#ifndef SIGNAL_ARGS
#define SIGNAL_ARGS  int postgres_signal_arg
#endif

/*
 * When there is no sigsetjmp, its functionality is provided by plain
 * setjmp. Incidentally, nothing provides setjmp's functionality in
 * that case.  We now support the case only on Windows.
 */
#ifdef WIN32
#define sigjmp_buf jmp_buf
#define sigsetjmp(x,y) setjmp(x)
#define siglongjmp longjmp
#endif

#if defined(HAVE_FDATASYNC) && !HAVE_DECL_FDATASYNC
extern int  fdatasync(int fildes);
#endif

/* If strtoq() exists, rename it to the more standard strtoll() */
#if defined(HAVE_LONG_LONG_INT_64) && !defined(HAVE_STRTOLL) && defined(HAVE_STRTOQ)
#define strtoll strtoq
#define HAVE_STRTOLL 1
#endif

/* If strtouq() exists, rename it to the more standard strtoull() */
#if defined(HAVE_LONG_LONG_INT_64) && !defined(HAVE_STRTOULL) && defined(HAVE_STRTOUQ)
#define strtoull strtouq
#define HAVE_STRTOULL 1
#endif

/*
 * We assume if we have these two functions, we have their friends too, and
 * can use the wide-character functions.
 */
#if defined(HAVE_WCSTOMBS) && defined(HAVE_TOWLOWER)
#define USE_WIDE_UPPER_LOWER
#endif

/* EXEC_BACKEND defines */
#ifdef EXEC_BACKEND
#define NON_EXEC_STATIC
#else
#define NON_EXEC_STATIC static
#endif

/* /port compatibility functions */
#include "port.h"

#endif                          /* C_H */