On 4 August 2014 12:37, Thomas Bany <mun.sysdev@gmail.com> wrote:

Hi everyone !

I experience troubles with NBExternalStructure in NativeBoost when the structure modeled contains fields with different types. For example, manipulating the following structure poses no problem and I can manipulate the fields correctly:

typedef struct abc_s {
double a;
double b;
double c;

} abc;

However, setting field 'a' to be an int yields the following symptoms:
�� From Pharo to C (function with 'abc' as argument type), the fields are badly read.

�� From C to Pharo (function with 'abc' as return type), the VM crash without an error nor a dump.

Am I doing something wrong or is it maybe specific to the compiler I use (the one that comes with Visual Studio Express 2013) ?

��

This caused by wrong alignment of structure in memory. Different compilers can align structures differently, and there's no way to know it at run time.

Try to change the #byteAlignment of the structure.
Also, if nothing helps, you can use dummy fields for padding fields, like in your example:

int a;
int dummy;
double b;
double c;
��

I'm pretty sure I could go arround this using NBExternalObject and building the structure on C side, but it would be nice to avoid it.

On a side note, my understanding is that creating a structure on Pharo side will have it stored in Pharo memory. Is it problematic when it comes to pass it by value ? Or should I manage the copying on the C heap to be safe ?

Thomas.

--
Best regards,
Igor Stasenko.