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Overview
Comment:The aggressive rounding behavior is now only accessible using the internal sqlite3MPrintf() function. The round() SQL function uses that internal function so it can access the aggressive rounding. But ordinary extensions and the format() SQL function cannot. Update: Superseded by round-up-2 branch
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SHA3-256: 3dec4b35ecd68a4dace7ea17f046231e25dd79d70f4702b82461cf98fd6f850e
User & Date: drh 2024-06-10 18:30:44
Original Comment: The aggressive rounding behavior is now only accessible using the internal sqlite3MPrintf() function. The round() SQL function uses that internal function so it can access the aggressive rounding. But ordinary extensions and the format() SQL function cannot.
Context
2024-06-10
18:30
The aggressive rounding behavior is now only accessible using the internal sqlite3MPrintf() function. The round() SQL function uses that internal function so it can access the aggressive rounding. But ordinary extensions and the format() SQL function cannot. Update: Superseded by round-up-2 branch (Closed-Leaf check-in: 3dec4b35 user: drh tags: round-up)
18:10
More aggressive rounding behavior for the round() function only. Format() still uses the classic behavior, and the same behavior exhibited by printf() in glibc. (check-in: a1b57288 user: drh tags: round-up)
Changes
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Changes to src/func.c.

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  ** otherwise use printf.
  */
  if( r<-4503599627370496.0 || r>+4503599627370496.0 ){
    /* The value has no fractional part so there is nothing to round */
  }else if( n==0 ){ 
    r = (double)((sqlite_int64)(r+(r<0?-0.5:+0.5)));
  }else{

    zBuf = sqlite3_mprintf("%#!.*f",n,r);
    if( zBuf==0 ){
      sqlite3_result_error_nomem(context);
      return;
    }
    sqlite3AtoF(zBuf, &r, sqlite3Strlen30(zBuf), SQLITE_UTF8);
    sqlite3_free(zBuf);
  }
  sqlite3_result_double(context, r);
}
#endif

/*
** Allocate nByte bytes of space using sqlite3Malloc(). If the








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  ** otherwise use printf.
  */
  if( r<-4503599627370496.0 || r>+4503599627370496.0 ){
    /* The value has no fractional part so there is nothing to round */
  }else if( n==0 ){ 
    r = (double)((sqlite_int64)(r+(r<0?-0.5:+0.5)));
  }else{
    sqlite3 *db = sqlite3_context_db_handle(context);
    zBuf = sqlite3MPrintf(db,"%!.*f",n,r);
    if( zBuf==0 ){
      sqlite3_result_error_nomem(context);
      return;
    }
    sqlite3AtoF(zBuf, &r, sqlite3Strlen30(zBuf), SQLITE_UTF8);
    sqlite3DbFreeNN(db, zBuf);
  }
  sqlite3_result_double(context, r);
}
#endif

/*
** Allocate nByte bytes of space using sqlite3Malloc(). If the
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Changes to src/printf.c.

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        break;
      case etFLOAT:
      case etEXP:
      case etGENERIC: {
        FpDecode s;
        int iRound;
        int j;


        if( bArgList ){
          realvalue = getDoubleArg(pArgList);
        }else{
          realvalue = va_arg(ap,double);
        }
        if( precision<0 ) precision = 6;         /* Set default precision */
#ifdef SQLITE_FP_PRECISION_LIMIT
        if( precision>SQLITE_FP_PRECISION_LIMIT ){
          precision = SQLITE_FP_PRECISION_LIMIT;
        }
#endif
        if( xtype==etFLOAT ){
          iRound = -precision;
        }else if( xtype==etGENERIC ){
          if( precision==0 ) precision = 1;
          iRound = precision;
        }else{
          iRound = precision+1;
        }





        sqlite3FpDecode(&s, realvalue, iRound, 
            flag_altform2 ? 26+flag_alternateform : 16);
            /*                 ^^^^^^^^^^^^^^^^^^^--- Undocumented behavior:
            ** When both '#' and '!' flags are present, the rounding behavior
            ** is changed.  See "rule 3" in the sqlite3FpDecode docs. */
        if( s.isSpecial ){
          if( s.isSpecial==2 ){
            bufpt = flag_zeropad ? "null" : "NaN";
            length = sqlite3Strlen30(bufpt);
            break;
          }else if( flag_zeropad ){
            s.z[0] = '9';








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        break;
      case etFLOAT:
      case etEXP:
      case etGENERIC: {
        FpDecode s;
        int iRound;
        int j;
        int mx;

        if( bArgList ){
          realvalue = getDoubleArg(pArgList);
        }else{
          realvalue = va_arg(ap,double);
        }
        if( precision<0 ) precision = 6;         /* Set default precision */
#ifdef SQLITE_FP_PRECISION_LIMIT
        if( precision>SQLITE_FP_PRECISION_LIMIT ){
          precision = SQLITE_FP_PRECISION_LIMIT;
        }
#endif
        if( xtype==etFLOAT ){
          iRound = -precision;
        }else if( xtype==etGENERIC ){
          if( precision==0 ) precision = 1;
          iRound = precision;
        }else{
          iRound = precision+1;
        }
        if( flag_altform2 ){
          mx = 26 + ((pAccum->printfFlags & SQLITE_PRINTF_INTERNAL)!=0);
        }else{
          mx = 16;
        }
        sqlite3FpDecode(&s, realvalue, iRound, mx);




        if( s.isSpecial ){
          if( s.isSpecial==2 ){
            bufpt = flag_zeropad ? "null" : "NaN";
            length = sqlite3Strlen30(bufpt);
            break;
          }else if( flag_zeropad ){
            s.z[0] = '9';
︙︙

Changes to src/util.c.

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** Rounding Behavior:
**
**   (1)  If the next digit is 3 or less, then truncate.  Do not round.
**
**   (2)  If the next digit is 5 or more, then round up.
**
**   (3)  Round up if the next digit is a 4 followed by three or
**        more 9 digits and all digits after the 4 up to the
**        antipenultimate digit are 9.  Otherwise truncate.
**

** Rule (3) is so that things like round(0.15,1) will come out as 0.2
** even though the stored value for 0.15 is really
** 0.1499999999999999944488848768742172978818416595458984375 and ought
** to round down to 0.1.  Rule (3) is only applied if mxRound==27.
**
** This routine is normally only called from printf()/format().  In that
** case, mxRound is usually 16 but is increased to 26 with the "!" flag.
** Undocumented behavior:  mxRound is 27 with the "#" and "!" flags.  The
** round() function uses this undocumented flag combination to activate
** rounding rule (3).
*/
void sqlite3FpDecode(FpDecode *p, double r, int iRound, int mxRound){
  int i;
  u64 v;
  int e, exp = 0;
  p->isSpecial = 0;
  p->z = p->zBuf;








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** Rounding Behavior:
**
**   (1)  If the next digit is 3 or less, then truncate.  Do not round.
**
**   (2)  If the next digit is 5 or more, then round up.
**
**   (3)  Round up if the next digit is a 4 followed by three or
**        more 9 digits and all significant digits after the 4 are
**        9 and mxRound is 27.  Otherwise truncate.
**
** Rule (3) is used by the built-in round() function to do more aggressive
** rounding so that things like round(0.15,1) will come out as 0.2
** even though the stored value for 0.15 is really
** 0.1499999999999999944488848768742172978818416595458984375 and ought
** to round down to 0.1.  Rule (3) is only applied if mxRound==27.


** And mxRound is only 27 if the internal sqlite3MPrintf() formatter is
** used and the "!" flag is included.


*/
void sqlite3FpDecode(FpDecode *p, double r, int iRound, int mxRound){
  int i;
  u64 v;
  int e, exp = 0;
  p->isSpecial = 0;
  p->z = p->zBuf;
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