src: enforce assumptions in FIXED_ONE_BYTE_STRING

[tniessen]

These functions are both meant to be used with a null-terminated and thus non-empty sequence of chars. However, there is nothing stopping call sites from passing zero-length sequences, which would certainly not be null-terminated and also would cause an underflow in N - 1. Therefore, this commit

• changes the size N of the array from int to std::size_t,
• ensures that compilation will fail if N = 0, and
• adds a runtime assertion that fails if the N-th char is not \0.

Note that the runtime assertion should be eliminated by any optimizing compiler when given a string literal, which is how these functions are used for the most part (though not exclusively).

[codecov[bot]]

Codecov Report

:x: Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 89.83%. Comparing base (b85e77b) to head (495fbf5). :warning: Report is 13 commits behind head on main.

Files with missing lines	Patch %	Lines
src/util.h	33.33%	0 Missing and 2 partials :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #58155      +/-   ##
==========================================
- Coverage   89.83%   89.83%   -0.01%     
==========================================
  Files         666      666              
  Lines      195340   195352      +12     
  Branches    38353    38362       +9     
==========================================
+ Hits       175492   175493       +1     
- Misses      12320    12327       +7     
- Partials     7528     7532       +4     

Files with missing lines	Coverage Δ
src/util.h	89.74% <33.33%> (-1.57%)	:arrow_down:

... and 32 files with indirect coverage changes

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[tniessen]

ping @nodejs/cpp-reviewers

[lemire]

I think that this PR is quite good as is.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/68637/

[tniessen]

One of the GitHub Actions workflows failed for unknown reasons and I do not see the usual option to retry. I suppose the only way is to force-push, which will then require a whole new CI run and re-approval.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/68839/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/68844/

[nodejs-github-bot]

Landed in f86b652bc8beec4aea778bfc621781264dfb6c6a