Add a SECP256K1_CONTEXT_ALL flag #559

1. 
   gwillen commented at 4:48 pm on October 1, 2018: none

   I recently learned that the typical use of libsecp contexts, in non-hot-path situations like during app startup of a heavyweight app, is just to give all the flags all the time.

   I think it would be slightly helpful to document this by creating a SECP256K1_CONTEXT_ALL flag, and commenting it with a note on when it’s appropriate to use (i.e. when a few dozen milliseconds aren’t a big deal.)

   CC: @apoelstra from earlier discussion

2. 
   gmaxwell commented at 11:51 am on June 7, 2019: contributor

   How should this work in a future where there are flags that turn on/off other behaviours and not just control what modes the libraries can be used in? e.g. I was considering a SECP256K1_NO_BIST to disable built in self-tests at context creation time.
3. 
   apoelstra commented at 7:57 am on June 8, 2019: contributor

   Heh, I guess we could learn from the many other projects that used “all” for a set of flags which later turned out to be incomplete.

   What if we created a flag SECP256K1_CONTEXT_DEFAULT which created both precomp tables and did the self-tests. Here “default” means “I have enough CPU and RAM that I don’t need to think about it”.

4. 
   real-or-random commented at 9:14 am on June 8, 2019: contributor

   Yep and “default” should then also mean “I’m aware that this may need more CPU and RAM in the future but I know this will never break my current API calls in the future”.
5. real-or-random cross-referenced this on Aug 3, 2022 from issue API cleanup with respect to contexts by real-or-random

Contributors
gwillen gmaxwell apoelstra real-or-random