Warning with clang 16

[wch]

I received an email from BDR about a warning from clang 16.

clang 16 is being prepared for release in early March, so it is time to start reporting its issues. See https://www.stats.ox.ac.uk/pub/bdr/clang16/ including its README.txt

From https://www.stats.ox.ac.uk/pub/bdr/clang16/httpuv.out:

Found the following significant warnings:
  httprequest.cpp:808:7: warning: ignoring return value of function declared with 'nodiscard' attribute [-Wunused-result]
See ‘/data/gannet/ripley/R/packages/tests-clang-trunk/httpuv.Rcheck/00install.out’ for details.

[wch]

The problem is here:

httpuv/src/httprequest.cpp

Line 808 in 650ba73

body.empty();

It calls .empty() on a vector, but that's the wrong method: it reports whether or not the vector is empty, but I believe the goal is to clear the vector, in which case the correct method is .clear().

[wch]

Looking at the history, the .empty() was originally introduced in bdaee93., and then was moved to a new location in 5178f6a.