provide PARI_SIGINT_block/pending address for cysignals

[kliem]

We provide the addresses of PARI_SIGINT_block and PARI_SIGINT_pending on runtime in python functions, such that cysignals can use it with try ... except ImportError.

[kliem]

@videlec

Any opinions about this approach? This would make it lots easier to build cysignals and cypari along with https://github.com/kliem/cysignals/tree/discover_cypari_on_runtime/src/cysignals.

The behaviour should be equivalent to the current approach.

[videlec]

Sounds reasonable. One problem I see with this approach is that loading cysignals will load cypari2 (or at least cypari2.paridecl). Ideally, cysignals should have an abstract mechanism to plug in third-party libraries signal handling. And then it would be the job of cypari2 to plug itself in cysignals at load time.

[kliem]

You mean that it should be cypari's responsibility to call a specialized sig_check and sig_on that sets the correct pointers for PARI_SIGINT_block and PARI_SIGINT_pending. Only problem I see with this is nested sig_on, but that could be made illegal for this case (so to the additional SIGINT_block SIGINT_pending the sig_on_count must always be 0).

[videlec]

Not sure I agree. I wanted to suggest that cysignals could be configurable via hooks. There should be a single implementation of sig_on/sig_off/sig_check inside cysignals. But it should be possible to plug extra steps to cysigs_interrupt_handler via hooks (one has to design a generic enough protocol though).

[kliem]

When should the hooks be called?

[videlec]

• cypari2 would insert its hooks in cysignals at load time of cypari2
• cysignals would call these hooks in its cysigs_interrupt_handler. More precisely, cysignals should have a stack of hooks and go through them any time an interruption occurs.

Maybe it is not feasible. I am trying to find a flexible enough solution so that cysignals becomes cypari2 agnostic.

[mkoeppe]

• cypari2 would insert its hooks in cysignals at load time of cypari2
• cysignals would call these hooks in its cysigs_interrupt_handler. More precisely, cysignals should have a stack of hooks and go through them any time an interruption occurs.

+1 on this approach

[mkoeppe]

@kliem Closing because it is superseded by #130 if I'm not mistaken