In 2.4 branch mod_deflate.c fails to compile if -Werror=format-overflow is specified. A patch has been committed to trunk. https://svn.apache.org/viewvc/httpd/httpd/trunk/modules/filters/mod_deflate.c?r1=1868313&r2=1874346
A similar error is present in mod_brotli and a patch has been committed in trunk. https://svn.apache.org/viewvc/httpd/httpd/trunk/modules/filters/mod_brotli.c?r1=1868313&r2=1874545
Created attachment 37049 [details] patch
Committed to 2.4 in revision r1874866.