Profile Guided Optimization (PGO) is a feature found in gcc and maybe other compilers.
With PGO, a build happens in several stages:
- the software is built with extra code for profile generation
- the software is run and profile information (e.g. counters of calls that are independent of system performance) recorded in .gcda files
- the software is built again using the information from .gcda files for optimization
This will create unreproducible binaries, unless all inputs in step 2 are constant.
Possible solutions:
- use constant input in step 2 (see gzip and libsamplerate below)
- remove .gcda files that differ across builds after step 2 (see bash below)
- disable PGO completely, losing some optimization
Seen in the wild:
- gcc
- python
make profile-opt - openSUSE/bash
- openSUSE/grep
- openSUSE/gzip
- openSUSE/libsamplerate
- GNU hello