Hello SQLite community,

We do embed SQLite in old/legacy devices (like Windows CE) with old Microsoft compiler like VS2005/VS2008/VS2010.

3.43 improves double arithmetic with long double and dekkerMul2() fallback algorithm. But, this is problematic for our builds. Updating the toolchain is not an option. Those targets also don't have long double support.

Troubleshooting the issue, I discovered that Microsoft compilers don't do double to unsigned 64bits conversion. The conversion is done on SIGNED 64bits.

https://stackoverflow.com/questions/3332440/safe-conversion-from-double-to-unsigned-64-bit-integer

SQLite 3.43.1 2023-09-11 12:25:57 4acd629be2bb593a2229bc95416120b600ecd828af596b26e62ac240a0ed45ad
msvc-1600 (32-bit)
sqlite> .testctrl uselongdouble
0
sqlite> select 1.1;
0.922337203685478
sqlite> .testctrl uselongdouble 1
1
sqlite> select 1.1;
1.1

we could use dynamic detection like
int CanCastDoubleToU64()
{
	double d = 1.1e19;
	u64 u = (u64)d;
	return (u&8000000000000000);
}
or add PRECOMPILER directives to workaround these compilers issues.

This would need to lower the precision checks with constants like

while( rr[0]<9.22e+17  ){
	exp -= 1;
	dekkerMul2(rr, 1.0e+01, 0.0);
}
in
SQLITE_PRIVATE void sqlite3FpDecode(FpDecode *p, double r, int iRound, int mxRound){

Regards,