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Overview
Comment:Fix the SQLITE_MIXED_ENDIAN_64BIT_FLOAT option so that it works on goofy linux kernels that employ CONFIG_FPE_FASTFPE. Patch from Frank van Vugt. (CVS 4339)
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SHA1: 71ab92e900512ad01047b46f734bd5f65998ecf9
User & Date: drh 2007-08-30 15:05:08
Context
2007-08-30
15:16
Fixes for malloc4.test. (CVS 4340) check-in: 23746924 user: danielk1977 tags: trunk
15:05
Fix the SQLITE_MIXED_ENDIAN_64BIT_FLOAT option so that it works on goofy linux kernels that employ CONFIG_FPE_FASTFPE. Patch from Frank van Vugt. (CVS 4339) check-in: 71ab92e9 user: drh tags: trunk
14:58
Fix a ref-count problem in the TCL bindings. Ticket #2597. (CVS 4338) check-in: 18a5babb user: drh tags: trunk
Changes
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Changes to src/vdbeaux.c.

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** I am also told that newer versions of GCC that follow a different
** ABI get the byte order right.
**
** Developers using SQLite on an ARM7 should compile and run their
** application using -DSQLITE_DEBUG=1 at least once.  With DEBUG
** enabled, some asserts below will ensure that the byte order of
** floating point values is correct.













*/
#ifdef SQLITE_MIXED_ENDIAN_64BIT_FLOAT
static double floatSwap(double in){

  union {
    double r;
    u32 i[2];
  } u;
  u32 t;

  u.r = in;
  t = u.i[0];
  u.i[0] = u.i[1];
................................................................................

  /* Integer and Real */
  if( serial_type<=7 && serial_type>0 ){
    u64 v;
    int i;
    if( serial_type==7 ){
      assert( sizeof(v)==sizeof(pMem->r) );
      swapMixedEndianFloat(pMem->r);
      memcpy(&v, &pMem->r, sizeof(v));

    }else{
      v = pMem->u.i;
    }
    len = i = sqlite3VdbeSerialTypeLen(serial_type);
    assert( len<=nBuf );
    while( i-- ){
      buf[i] = (v&0xFF);
................................................................................
      /* Verify that integers and floating point values use the same
      ** byte order.  Or, that if SQLITE_MIXED_ENDIAN_64BIT_FLOAT is
      ** defined that 64-bit floating point values really are mixed
      ** endian.
      */
      static const u64 t1 = ((u64)0x3ff00000)<<32;
      static const double r1 = 1.0;
      double r2 = r1;
      swapMixedEndianFloat(r2);
      assert( sizeof(r2)==sizeof(t1) && memcmp(&r2, &t1, sizeof(r1))==0 );
#endif

      x = (buf[0]<<24) | (buf[1]<<16) | (buf[2]<<8) | buf[3];
      y = (buf[4]<<24) | (buf[5]<<16) | (buf[6]<<8) | buf[7];
      x = (x<<32) | y;
      if( serial_type==6 ){
        pMem->u.i = *(i64*)&x;
        pMem->flags = MEM_Int;
      }else{
        assert( sizeof(x)==8 && sizeof(pMem->r)==8 );

        memcpy(&pMem->r, &x, sizeof(x));
        swapMixedEndianFloat(pMem->r);
        pMem->flags = MEM_Real;
      }
      return 8;
    }
    case 8:    /* Integer 0 */
    case 9: {  /* Integer 1 */
      pMem->u.i = serial_type-8;







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** I am also told that newer versions of GCC that follow a different
** ABI get the byte order right.
**
** Developers using SQLite on an ARM7 should compile and run their
** application using -DSQLITE_DEBUG=1 at least once.  With DEBUG
** enabled, some asserts below will ensure that the byte order of
** floating point values is correct.
**
** (2007-08-30)  Frank van Vugt has studied this problem closely
** and has send his findings to the SQLite developers.  Frank
** writes that some Linux kernels offer floating point hardware
** emulation that uses only 32-bit mantissas instead of a full 
** 48-bits as required by the IEEE standard.  (This is the
** CONFIG_FPE_FASTFPE option.)  On such systems, floating point
** byte swapping becomes very complicated.  To avoid problems,
** the necessary byte swapping is carried out using a 64-bit integer
** rather than a 64-bit float.  Frank assures us that the code here
** works for him.  We, the developers, have no way to independently
** verify this, but Frank seems to know what he is talking about
** so we trust him.
*/
#ifdef SQLITE_MIXED_ENDIAN_64BIT_FLOAT

static u64 floatSwap(u64 in){
  union {
    u64 r;
    u32 i[2];
  } u;
  u32 t;

  u.r = in;
  t = u.i[0];
  u.i[0] = u.i[1];
................................................................................

  /* Integer and Real */
  if( serial_type<=7 && serial_type>0 ){
    u64 v;
    int i;
    if( serial_type==7 ){
      assert( sizeof(v)==sizeof(pMem->r) );

      memcpy(&v, &pMem->r, sizeof(v));
      swapMixedEndianFloat(v);
    }else{
      v = pMem->u.i;
    }
    len = i = sqlite3VdbeSerialTypeLen(serial_type);
    assert( len<=nBuf );
    while( i-- ){
      buf[i] = (v&0xFF);
................................................................................
      /* Verify that integers and floating point values use the same
      ** byte order.  Or, that if SQLITE_MIXED_ENDIAN_64BIT_FLOAT is
      ** defined that 64-bit floating point values really are mixed
      ** endian.
      */
      static const u64 t1 = ((u64)0x3ff00000)<<32;
      static const double r1 = 1.0;
      u64 t2 = t1;
      swapMixedEndianFloat(t2);
      assert( sizeof(r1)==sizeof(t2) && memcmp(&r1, &t2, sizeof(r1))==0 );
#endif

      x = (buf[0]<<24) | (buf[1]<<16) | (buf[2]<<8) | buf[3];
      y = (buf[4]<<24) | (buf[5]<<16) | (buf[6]<<8) | buf[7];
      x = (x<<32) | y;
      if( serial_type==6 ){
        pMem->u.i = *(i64*)&x;
        pMem->flags = MEM_Int;
      }else{
        assert( sizeof(x)==8 && sizeof(pMem->r)==8 );
        swapMixedEndianFloat(x);
        memcpy(&pMem->r, &x, sizeof(x));

        pMem->flags = MEM_Real;
      }
      return 8;
    }
    case 8:    /* Integer 0 */
    case 9: {  /* Integer 1 */
      pMem->u.i = serial_type-8;