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Overview
Comment:Improved implementation of 64-bit signed integer multiply that correctly detects overflow (and promotes to floating-point) in some corner cases. Fix for ticket [1ec41379c9c1e400]
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SHA1: db3ebd7c52cfc5fcc7be00f52e9d7c84719f7b93
User & Date: drh 2016-09-20 22:04:05
Context
2016-09-21
14:41
Update the fts5vocab table to handle "ORDER BY term" efficiently. (check-in: d4928fb5 user: dan tags: trunk)
2016-09-20
22:04
Improved implementation of 64-bit signed integer multiply that correctly detects overflow (and promotes to floating-point) in some corner cases. Fix for ticket [1ec41379c9c1e400] (check-in: db3ebd7c user: drh tags: trunk)
17:49
Fix harmless compiler warning. (check-in: 72429063 user: mistachkin tags: trunk)
Changes
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Changes to src/util.c.

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    if( (*pA)>=0 ) return 1;
    *pA -= iB;
    return 0;
  }else{
    return sqlite3AddInt64(pA, -iB);
  }
}
#define TWOPOWER32 (((i64)1)<<32)
#define TWOPOWER31 (((i64)1)<<31)
int sqlite3MulInt64(i64 *pA, i64 iB){
  i64 iA = *pA;
  i64 iA1, iA0, iB1, iB0, r;

  iA1 = iA/TWOPOWER32;
  iA0 = iA % TWOPOWER32;
  iB1 = iB/TWOPOWER32;
  iB0 = iB % TWOPOWER32;
  if( iA1==0 ){

    if( iB1==0 ){
      *pA *= iB;
      return 0;

    }
    r = iA0*iB1;
  }else if( iB1==0 ){
    r = iA1*iB0;
  }else{
    /* If both iA1 and iB1 are non-zero, overflow will result */
    return 1;
  }
  testcase( r==(-TWOPOWER31)-1 );
  testcase( r==(-TWOPOWER31) );
  testcase( r==TWOPOWER31 );
  testcase( r==TWOPOWER31-1 );
  if( r<(-TWOPOWER31) || r>=TWOPOWER31 ) return 1;
  r *= TWOPOWER32;
  if( sqlite3AddInt64(&r, iA0*iB0) ) return 1;
  *pA = r;
  return 0;
}

/*
** Compute the absolute value of a 32-bit signed integer, of possible.  Or 
** if the integer has a value of -2147483648, return +2147483647
*/







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    if( (*pA)>=0 ) return 1;
    *pA -= iB;
    return 0;
  }else{
    return sqlite3AddInt64(pA, -iB);
  }
}


int sqlite3MulInt64(i64 *pA, i64 iB){
  i64 iA = *pA;
  if( iB>0 ){
    if( iA>LARGEST_INT64/iB ) return 1;
    if( iA<SMALLEST_INT64/iB ) return 1;

  }else if( iB<0 ){

    if( iA>0 ){
      if( iB<SMALLEST_INT64/iA ) return 1;
    }else if( iA<0 ){
      if( iB==SMALLEST_INT64 ) return 1;
      if( iA==SMALLEST_INT64 ) return 1;
      if( -iA>LARGEST_INT64/-iB ) return 1;
    }






  }







  *pA = iA*iB;
  return 0;
}

/*
** Compute the absolute value of a 32-bit signed integer, of possible.  Or 
** if the integer has a value of -2147483648, return +2147483647
*/

Changes to test/expr.test.

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  test_realnum_expr expr-1.255\
      {i1=4294967296, i2=-2147483647} {i1*i2}     -9223372032559808512
  test_realnum_expr expr-1.256\
      {i1=-4294967296, i2=-2147483648} {i1*i2}    9.22337203685478e+18
  test_realnum_expr expr-1.257\
      {i1=-4294967296, i2=-2147483647} {i1*i2}    9223372032559808512




























}}

ifcapable floatingpoint {
  test_expr expr-2.1 {r1=1.23, r2=2.34} {r1+r2} 3.57
  test_expr expr-2.2 {r1=1.23, r2=2.34} {r1-r2} -1.11
  test_expr expr-2.3 {r1=1.23, r2=2.34} {r1*r2} 2.8782
}







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  test_realnum_expr expr-1.255\
      {i1=4294967296, i2=-2147483647} {i1*i2}     -9223372032559808512
  test_realnum_expr expr-1.256\
      {i1=-4294967296, i2=-2147483648} {i1*i2}    9.22337203685478e+18
  test_realnum_expr expr-1.257\
      {i1=-4294967296, i2=-2147483647} {i1*i2}    9223372032559808512

  test_realnum_expr expr-1.260\
      {i1=3037000500, i2=3037000500} {i1*i2}      9.22337203700025e+18
  test_realnum_expr expr-1.261\
      {i1=3037000500, i2=-3037000500} {i1*i2}     -9.22337203700025e+18
  test_realnum_expr expr-1.262\
      {i1=-3037000500, i2=3037000500} {i1*i2}     -9.22337203700025e+18
  test_realnum_expr expr-1.263\
      {i1=-3037000500, i2=-3037000500} {i1*i2}    9.22337203700025e+18

  test_realnum_expr expr-1.264\
      {i1=3037000500, i2=3037000499} {i1*i2}      9223372033963249500
  test_realnum_expr expr-1.265\
      {i1=3037000500, i2=-3037000499} {i1*i2}     -9223372033963249500
  test_realnum_expr expr-1.266\
      {i1=-3037000500, i2=3037000499} {i1*i2}     -9223372033963249500
  test_realnum_expr expr-1.267\
      {i1=-3037000500, i2=-3037000499} {i1*i2}    9223372033963249500

  test_realnum_expr expr-1.268\
      {i1=3037000499, i2=3037000500} {i1*i2}      9223372033963249500
  test_realnum_expr expr-1.269\
      {i1=3037000499, i2=-3037000500} {i1*i2}     -9223372033963249500
  test_realnum_expr expr-1.270\
      {i1=-3037000499, i2=3037000500} {i1*i2}     -9223372033963249500
  test_realnum_expr expr-1.271\
      {i1=-3037000499, i2=-3037000500} {i1*i2}    9223372033963249500

}}

ifcapable floatingpoint {
  test_expr expr-2.1 {r1=1.23, r2=2.34} {r1+r2} 3.57
  test_expr expr-2.2 {r1=1.23, r2=2.34} {r1-r2} -1.11
  test_expr expr-2.3 {r1=1.23, r2=2.34} {r1*r2} 2.8782
}