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Using LotusScript C-Callouts on non-32-bit Platforms
There are a few issues you need to be aware of if you're writing or porting LotusScript C-Callouts to non-32-bit platforms.
The non-32-bit platforms fall into two categories: 64-bit (Windows 64, AIX-64, Linux-64) and 128-bit (iSeries)
When is a long not a long?
An important thing to consider is that LotusScript data types are the same size across all platforms. A LotusScript
byte is always one byte (a Notes
BYTE in C),
integer is always 2 bytes (a Notes
WORD in C) and a
long is always 4 bytes (a Notes
DWORD in C). In contrast, a C
long is not a fixed width across platforms, or even compilers. In the Notes 8 builds, a long is 4 bytes on Windows-64, but 8 bytes on AIX-64, SUSE Linux-64 and zLinux64.
In order to check how many bytes a long and a pointer is on a given platform, compile and run the following simple C program:
main()
{
printf("sizeof long is: %d, pointer is %d\n", sizeof (long), sizeof (long *));
}
You need to make sure that the size of the LotusScript data that you're passing to the C-Callout matches the arguments in C of the C-Callout itself. There were some bugs in C-Callouts on 64-bit platforms that have been fixed in Notes/Domino 8.5.2.
Pointers
Pointers are a more straightforward issue (except on iSeries). On all 64-bit platforms, you can pass and return 8-byte pointers by using the LotusScript
double datatype. However, you
cannot manipulate these objects on the LotusScript side. Your C-Callout can return a pointer in a double, and then in LotusScript you can call another C-Callout with the double parameter to a C pointer, but you must not change the value of the double in LotusScript. Just as is the case with scalar types, the size of the LotusScript data must match the size of the corresponding argument in the C code.
iSeries has it's own issue in that pointers are 16-bytes long. Since no LotusScript data type is that big, you cannot pass pointers or return pointers via C-Callouts on iSeries.