Fix serialising of null `const char*` and improve handling of string litterals and function pointers

[cschreib]

Fixes #107.

[codecov[bot]]

Codecov Report

Merging #109 (ebfda65) into main (e557246) will decrease coverage by 0.09%. The diff coverage is 100.00%.

Additional details and impacted files

[](https://app.codecov.io/gh/cschreib/snitch/pull/109?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Corentin+Schreiber) ```diff @@ Coverage Diff @@ ## main #109 +/- ## ========================================== - Coverage 93.39% 93.31% -0.09% ========================================== Files 23 23 Lines 1257 1256 -1 ========================================== - Hits 1174 1172 -2 - Misses 83 84 +1 ``` | [Impacted Files](https://app.codecov.io/gh/cschreib/snitch/pull/109?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Corentin+Schreiber) | Coverage Δ | | |---|---|---| | [include/snitch/snitch\_append.hpp](https://app.codecov.io/gh/cschreib/snitch/pull/109?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Corentin+Schreiber#diff-aW5jbHVkZS9zbml0Y2gvc25pdGNoX2FwcGVuZC5ocHA=) | `96.12% <100.00%> (-0.03%)` | :arrow_down: | ... and [1 file with indirect coverage changes](https://app.codecov.io/gh/cschreib/snitch/pull/109/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Corentin+Schreiber) ------ [Continue to review full report in Codecov by Sentry](https://app.codecov.io/gh/cschreib/snitch/pull/109?src=pr&el=continue&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Corentin+Schreiber). > **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Corentin+Schreiber) > `Δ = absolute (impact)`, `ø = not affected`, `? = missing data` > Powered by [Codecov](https://app.codecov.io/gh/cschreib/snitch/pull/109?src=pr&el=footer&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Corentin+Schreiber). Last update [e557246...ebfda65](https://app.codecov.io/gh/cschreib/snitch/pull/109?src=pr&el=lastupdated&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Corentin+Schreiber). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Corentin+Schreiber).