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SQLite training in Houston TX on 2019-11-05 (details)
Part of the 2019 Tcl Conference

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Overview
Comment:Use the CLANG_VERSION macro to control clang-specific features.
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Timelines: family | ancestors | descendants | both | gnu-safe-math
Files: files | file ages | folders
SHA1: f8ebeec211483503e135104ef977b3c384a1d789
User & Date: drh 2017-01-03 20:01:24
Context
2017-01-03
21:03
Fix a typo in a comment. check-in: ae087123 user: drh tags: gnu-safe-math
20:01
Use the CLANG_VERSION macro to control clang-specific features. check-in: f8ebeec2 user: drh tags: gnu-safe-math
18:05
Use the GCC built-in __sync_fetch_and_sub() to make the sqlite3StatusDown() routine atomic, and thereby avoid some mutexing. check-in: f69ce75b user: drh tags: gnu-safe-math
Changes
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Changes to src/sqliteInt.h.

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/* What version of GCC is being used.  0 means GCC is not being used */
#ifdef __GNUC__
# define GCC_VERSION (__GNUC__*1000000+__GNUC_MINOR__*1000+__GNUC_PATCHLEVEL__)
#else
# define GCC_VERSION 0
#endif









/* Needed for various definitions... */
#if defined(__GNUC__) && !defined(_GNU_SOURCE)
# define _GNU_SOURCE
#endif

#if defined(__OpenBSD__) && !defined(_BSD_SOURCE)
................................................................................
#endif

/*
** The SQLITE_ATOMIC_STATUS_DOWN macro is defined if and only if
** the sqlite3StatusDown() function is threadsafe.
*/
#if !defined(SQLITE_DISABLE_INTRINSIC) \
    && defined(__GNUC__) && GCC_VERSION>=4004000
# define SQLITE_ATOMIC_STATUS_DOWN 1
#endif

/*
** Make sure that the compiler intrinsics we desire are enabled when
** compiling with an appropriate version of MSVC unless prevented by
** the SQLITE_DISABLE_INTRINSIC define.







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/* What version of GCC is being used.  0 means GCC is not being used */
#ifdef __GNUC__
# define GCC_VERSION (__GNUC__*1000000+__GNUC_MINOR__*1000+__GNUC_PATCHLEVEL__)
#else
# define GCC_VERSION 0
#endif

/* What version of CLANG is being used.  0 means GCC is not being used */
#ifdef __clang__
# define CLANG_VERSION \
            (__clang_major__*1000000+__clang_minor__*1000+__clang_patchlevel__)
#else
# define CLANG_VERSION 0
#endif

/* Needed for various definitions... */
#if defined(__GNUC__) && !defined(_GNU_SOURCE)
# define _GNU_SOURCE
#endif

#if defined(__OpenBSD__) && !defined(_BSD_SOURCE)
................................................................................
#endif

/*
** The SQLITE_ATOMIC_STATUS_DOWN macro is defined if and only if
** the sqlite3StatusDown() function is threadsafe.
*/
#if !defined(SQLITE_DISABLE_INTRINSIC) \
    && (GCC_VERSION>=4004000 || CLANG_VERSION>=3000000)
# define SQLITE_ATOMIC_STATUS_DOWN 1
#endif

/*
** Make sure that the compiler intrinsics we desire are enabled when
** compiling with an appropriate version of MSVC unless prevented by
** the SQLITE_DISABLE_INTRINSIC define.

Changes to src/status.c.

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  }
}
void sqlite3StatusDown(int op, int N){
  wsdStatInit;
  assert( N>=0 );
  assert( op>=0 && op<ArraySize(wsdStat.nowValue) );
#if !defined(SQLITE_DISABLE_INTRINSIC) \
    && defined(__GNUC__) && GCC_VERSION>=4004000
  (void)__sync_fetch_and_sub(&wsdStat.nowValue[op], N);
#else
  assert( op>=0 && op<ArraySize(statMutex) );
  assert( sqlite3_mutex_held(statMutex[op] ? sqlite3Pcache1Mutex()
                                           : sqlite3MallocMutex()) );
  wsdStat.nowValue[op] -= N;
#endif







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  }
}
void sqlite3StatusDown(int op, int N){
  wsdStatInit;
  assert( N>=0 );
  assert( op>=0 && op<ArraySize(wsdStat.nowValue) );
#if !defined(SQLITE_DISABLE_INTRINSIC) \
    && (GCC_VERSION>=4004000 || CLANG_VERSION>=3000000)
  (void)__sync_fetch_and_sub(&wsdStat.nowValue[op], N);
#else
  assert( op>=0 && op<ArraySize(statMutex) );
  assert( sqlite3_mutex_held(statMutex[op] ? sqlite3Pcache1Mutex()
                                           : sqlite3MallocMutex()) );
  wsdStat.nowValue[op] -= N;
#endif

Changes to src/util.c.

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*/
u32 sqlite3Get4byte(const u8 *p){
#if SQLITE_BYTEORDER==4321
  u32 x;
  memcpy(&x,p,4);
  return x;
#elif SQLITE_BYTEORDER==1234 && !defined(SQLITE_DISABLE_INTRINSIC) \
    && defined(__GNUC__) && GCC_VERSION>=4003000
  u32 x;
  memcpy(&x,p,4);
  return __builtin_bswap32(x);
#elif SQLITE_BYTEORDER==1234 && !defined(SQLITE_DISABLE_INTRINSIC) \
    && defined(_MSC_VER) && _MSC_VER>=1300
  u32 x;
  memcpy(&x,p,4);
................................................................................
  return ((unsigned)p[0]<<24) | (p[1]<<16) | (p[2]<<8) | p[3];
#endif
}
void sqlite3Put4byte(unsigned char *p, u32 v){
#if SQLITE_BYTEORDER==4321
  memcpy(p,&v,4);
#elif SQLITE_BYTEORDER==1234 && !defined(SQLITE_DISABLE_INTRINSIC) \
    && defined(__GNUC__) && GCC_VERSION>=4003000
  u32 x = __builtin_bswap32(v);
  memcpy(p,&x,4);
#elif SQLITE_BYTEORDER==1234 && !defined(SQLITE_DISABLE_INTRINSIC) \
    && defined(_MSC_VER) && _MSC_VER>=1300
  u32 x = _byteswap_ulong(v);
  memcpy(p,&x,4);
#else
................................................................................
** Attempt to add, substract, or multiply the 64-bit signed value iB against
** the other 64-bit signed integer at *pA and store the result in *pA.
** Return 0 on success.  Or if the operation would have resulted in an
** overflow, leave *pA unchanged and return 1.
*/
int sqlite3AddInt64(i64 *pA, i64 iB){
#if !defined(SQLITE_DISABLE_INTRINSIC) \
    && defined(__GNUC__) && GCC_VERSION>=5004000
  return __builtin_add_overflow(*pA, iB, pA);
#else
  i64 iA = *pA;
  testcase( iA==0 ); testcase( iA==1 );
  testcase( iB==-1 ); testcase( iB==0 );
  if( iB>=0 ){
    testcase( iA>0 && LARGEST_INT64 - iA == iB );
................................................................................
  }
  *pA += iB;
  return 0; 
#endif
}
int sqlite3SubInt64(i64 *pA, i64 iB){
#if !defined(SQLITE_DISABLE_INTRINSIC) \
    && defined(__GNUC__) && GCC_VERSION>=5004000
  return __builtin_sub_overflow(*pA, iB, pA);
#else
  testcase( iB==SMALLEST_INT64+1 );
  if( iB==SMALLEST_INT64 ){
    testcase( (*pA)==(-1) ); testcase( (*pA)==0 );
    if( (*pA)>=0 ) return 1;
    *pA -= iB;
................................................................................
  }else{
    return sqlite3AddInt64(pA, -iB);
  }
#endif
}
int sqlite3MulInt64(i64 *pA, i64 iB){
#if !defined(SQLITE_DISABLE_INTRINSIC) \
    && defined(__GNUC__) && GCC_VERSION>=5004000
  return __builtin_mul_overflow(*pA, iB, pA);
#else
  i64 iA = *pA;
  if( iB>0 ){
    if( iA>LARGEST_INT64/iB ) return 1;
    if( iA<SMALLEST_INT64/iB ) return 1;
  }else if( iB<0 ){







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*/
u32 sqlite3Get4byte(const u8 *p){
#if SQLITE_BYTEORDER==4321
  u32 x;
  memcpy(&x,p,4);
  return x;
#elif SQLITE_BYTEORDER==1234 && !defined(SQLITE_DISABLE_INTRINSIC) \
    && (GCC_VERSION>=4003000 || CLANG_VERSION>=3000000)
  u32 x;
  memcpy(&x,p,4);
  return __builtin_bswap32(x);
#elif SQLITE_BYTEORDER==1234 && !defined(SQLITE_DISABLE_INTRINSIC) \
    && defined(_MSC_VER) && _MSC_VER>=1300
  u32 x;
  memcpy(&x,p,4);
................................................................................
  return ((unsigned)p[0]<<24) | (p[1]<<16) | (p[2]<<8) | p[3];
#endif
}
void sqlite3Put4byte(unsigned char *p, u32 v){
#if SQLITE_BYTEORDER==4321
  memcpy(p,&v,4);
#elif SQLITE_BYTEORDER==1234 && !defined(SQLITE_DISABLE_INTRINSIC) \
    && (GCC_VERSION>=4003000 || CLANG_VERSION>=3000000)
  u32 x = __builtin_bswap32(v);
  memcpy(p,&x,4);
#elif SQLITE_BYTEORDER==1234 && !defined(SQLITE_DISABLE_INTRINSIC) \
    && defined(_MSC_VER) && _MSC_VER>=1300
  u32 x = _byteswap_ulong(v);
  memcpy(p,&x,4);
#else
................................................................................
** Attempt to add, substract, or multiply the 64-bit signed value iB against
** the other 64-bit signed integer at *pA and store the result in *pA.
** Return 0 on success.  Or if the operation would have resulted in an
** overflow, leave *pA unchanged and return 1.
*/
int sqlite3AddInt64(i64 *pA, i64 iB){
#if !defined(SQLITE_DISABLE_INTRINSIC) \
    && (GCC_VERSION>=5004000 || CLANG_VERSION>=4000000)
  return __builtin_add_overflow(*pA, iB, pA);
#else
  i64 iA = *pA;
  testcase( iA==0 ); testcase( iA==1 );
  testcase( iB==-1 ); testcase( iB==0 );
  if( iB>=0 ){
    testcase( iA>0 && LARGEST_INT64 - iA == iB );
................................................................................
  }
  *pA += iB;
  return 0; 
#endif
}
int sqlite3SubInt64(i64 *pA, i64 iB){
#if !defined(SQLITE_DISABLE_INTRINSIC) \
    && (GCC_VERSION>=5004000 || CLANG_VERSION>=4000000)
  return __builtin_sub_overflow(*pA, iB, pA);
#else
  testcase( iB==SMALLEST_INT64+1 );
  if( iB==SMALLEST_INT64 ){
    testcase( (*pA)==(-1) ); testcase( (*pA)==0 );
    if( (*pA)>=0 ) return 1;
    *pA -= iB;
................................................................................
  }else{
    return sqlite3AddInt64(pA, -iB);
  }
#endif
}
int sqlite3MulInt64(i64 *pA, i64 iB){
#if !defined(SQLITE_DISABLE_INTRINSIC) \
    && (GCC_VERSION>=5004000 || CLANG_VERSION>=4000000)
  return __builtin_mul_overflow(*pA, iB, pA);
#else
  i64 iA = *pA;
  if( iB>0 ){
    if( iA>LARGEST_INT64/iB ) return 1;
    if( iA<SMALLEST_INT64/iB ) return 1;
  }else if( iB<0 ){