Fix cmake install missing http_endpoint_calculation_mode.h

[spottsdd]

Summary

• tracer_config.h (a public header) includes http_endpoint_calculation_mode.h, but that file is missing from the public_headers FILE_SET list in CMakeLists.txt.
• As a result, cmake --install never copies http_endpoint_calculation_mode.h to the install prefix's include/datadog/ directory, even though the file exists in the source tree.
• Anyone building from source and installing per the README's manual build instructions gets a fatal compile error on anything that includes tracer.h/tracer_config.h:

  fatal error: http_endpoint_calculation_mode.h: No such file or directory
  

• Added the missing entry to the FILE_SET list, alphabetically placed next to the other http_* header.

Recreated from #341, which was opened from a fork; this one is opened from a branch on the main repo instead.

Test plan

• Confirmed by diffing the FILES list in CMakeLists.txt against the actual contents of include/datadog/ in the source tree — this was the only header present in the tree but absent from the list.
• Hit this exact error downstream while building a lab exercise against a manually-built/installed v2.1.1: cmake -B build . && cmake --build build -j && cmake --install build, then compiling a file that includes <datadog/tracer.h> failed with the error above.

Made with Cursor

[pr-commenter]

Benchmarks

Benchmark execution time: 2026-07-24 13:38:14

Comparing candidate commit f634ffe in PR branch fix/install-missing-header with baseline commit 24f765c in branch main.

Found 0 performance improvements and 1 performance regressions! Performance is the same for 7 metrics, 0 unstable metrics.

Explanation

This is an A/B test comparing a candidate commit's performance against that of a baseline commit. Performance changes are noted in the tables below as:

• 🟩 = significantly better candidate vs. baseline
• 🟥 = significantly worse candidate vs. baseline

We compute a confidence interval (CI) over the relative difference of means between metrics from the candidate and baseline commits, considering the baseline as the reference.

If the CI is entirely outside the configured SIGNIFICANT_IMPACT_THRESHOLD (or the deprecated UNCONFIDENCE_THRESHOLD), the change is considered significant.

Feel free to reach out to #apm-benchmarking-platform on Slack if you have any questions.

More details about the CI and significant changes

You can imagine this CI as a range of values that is likely to contain the true difference of means between the candidate and baseline commits.

CIs of the difference of means are often centered around 0%, because often changes are not that big:

---------------------------------(------|---^--------)-------------------------------->
                              -0.6%    0%  0.3%     +1.2%
                                 |          |        |
         lower bound of the CI --'          |        |
sample mean (center of the CI) -------------'        |
         upper bound of the CI ----------------------'

As described above, a change is considered significant if the CI is entirely outside the configured SIGNIFICANT_IMPACT_THRESHOLD (or the deprecated UNCONFIDENCE_THRESHOLD).

For instance, for an execution time metric, this confidence interval indicates a significantly worse performance:

----------------------------------------|---------|---(---------^---------)---------->
                                       0%        1%  1.3%      2.2%      3.1%
                                                  |   |         |         |
       significant impact threshold --------------'   |         |         |
                      lower bound of CI --------------'         |         |
       sample mean (center of the CI) --------------------------'         |
                      upper bound of CI ----------------------------------'

scenario:BM_TraceID_ParseHex/128bit

• 🟥 execution_time [+2.866ns; +2.882ns] or [+2.344%; +2.357%]

[datadog-official]

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 91.75% (+0.00%)

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: f634ffe | Docs | Datadog PR Page | Give us feedback!}