I am yet again stuck with a problem that pops up sometimes but quite often nevertheless. I suspect I am misusing the foreign language interface so this might be just a code review. What I am doing wrong is probably how I deal with options that I have declared in PL_option_t but were not provided by…

[image] Boris: PS: if anyone is wondering, I ended up here because I thought it was gonna be quite easy :smiley: You are quite close :slight_smile: I think @peter.ludemann is right that the C++ interface is easier. Also note that there is also "prosqlite" pack for SWI-Prolog . The real m…

Might I suggest using the C++ interface rather than C? The C++ interface has built-in checking for errors (doesn’t require checking the return code from every PL_*() call), so it’s less error-prone. A small style point: instead of if (TRUE != PL_get_chars(...)) you can write if (!PL_get_chars(...). …

[image] jan: mode must be a term_t, but it is an atom_t That’s a mistake I’ve made a number of times. We’ve discussed preventing this by wrapping atom_t and term_t as C structs, but it was unclear if the compilers would generate as good code. Also, it’d be quite a bit of work (I experimented …

Yes, thank you, this was it. I thought about this for a second but then it compiled and the thought seized. [image] jan: there is also “prosqlite” pack for SWI-Prolog . Yes, and there is also the ODBC library. I wanted to see if I can do something interesting with the compiled statements that…

[image] Boris: I have barely any hands-on experience with C++ and I want to tackle the novelties one by one :slight_smile: C++ can be treated as a “better C than C”; that is, you could write mostly in a C style (although you might need to know something about how exceptions work) … I could pr…

[image] jan: That is a common issue when using PL_scan_options() when you want an additional check on the value. I considered several times to just pick up the defines from sqlite and drop them in the Prolog wrapper of the sqlite bindings; then parse the options in Prolog and give the flags a…

I would gladly take your offer but maybe it is a bit preliminary. And, most of the real fun is figuring out how to do it, right? On the other hand, there is very little code right now, so little work for you and easy to figure out for me. Here is what I have after I fixed the C code. swiplite.c (3.…

Here’s a very quick conversion of your code to C++ (untested). This reminded me that I was going to improve the interface to PL_scan_options(). Also, I think some of the calls to PL_() and Plx_() functions in the C++ code can be improved (e.g., the PlEx<bool>(dbname.get_chars(...)) can probably be r…

Erratic behaviour when raising exception from foreign code

Help!

jan Split this topic May 31, 2024, 6:56am 10

3 posts were split to a new topic: A safer C API

Topic		Replies	Views
A safer C API Discussion	3	178	May 31, 2024
PL_get_integer returns false even with confirmed integer term_t Help! ffi	10	161	January 24, 2025
Exception in foreign c++ code Help! how-to	1	437	September 30, 2021
C++ foreign interface error Pack	5	354	September 10, 2023
Install/use swi-prolog for C++ General	16	823	August 19, 2023

Erratic behaviour when raising exception from foreign code

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