clang (even with no args) takes 0.7 seconds to execute

$ time nonexistent-command
zsh: command not found: nonexistent-command
nonexistent-command 0.00s user 0.00s system 0% cpu 0.425 total
$ time clang
clang: error: no input files
clang 0.01s user 0.68s system 40% cpu 1.682 total

Since clang is invoked every time ./configure tries a C/C++ snippet, running configure on a project takes something like 5-10 minutes.

$ time ./configure
[...]
./configure 29.65s user 542.02s system 96% cpu 9:50.57 total

I've managed to track this down to a call to fparseln inside the clang binary, but that's it.

Instruments SS:

Corresponding assembler inside clang:

This issue is appearing for me and for my coworkers, but not for others I've asked. It happened both on High Sierra and on Catalina (I tried upgrading, but that did not fix it).

Everyone on a mac at my office has this issue, so it may be something the IT grunts installed, but no idea what or how to find it. Ideas on how to proceed and/or fix?

1 Answer

As this only affected people inside my office, I suspected it was some software that the company installed. Turns out I was right:

Cylance was causing this issue.