google/benchmark

[BUG] pkg-config file is broken when CMAKE_INSTALL_{INCLUDE,LIB}DIR is absolute

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#1,396 opened on May 16, 2022

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help wanted

Description

Describe the bug

As per title: cmake/benchmark.pc.in has

prefix=@CMAKE_INSTALL_PREFIX@
exec_prefix=${prefix}
libdir=${prefix}/@CMAKE_INSTALL_LIBDIR@
includedir=${prefix}/@CMAKE_INSTALL_INCLUDEDIR@

and so can’t handle absolute paths in CMAKE_INSTALL_{INCLUDE,LIB}DIR. This leads to broken .pc files on NixOS in particular.

Identical to https://github.com/libjxl/libjxl/issues/1400 (fixed). See “Concatenating paths when building pkg-config files” for a thorough discussion of the problem and a suggested fix, or KDE’s extra-cmake-modules for a simpler approach.

System

$ uname -a
Linux localhost 5.15.36 #1-NixOS SMP Wed Apr 27 12:39:02 UTC 2022 x86_64 GNU/Linux

Contributor guide

Tech stack
cpp
Domain
build system
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Basic understanding of CMakeFamiliarity with pkg config file format
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70
Research direction
The bug is in the cmake/benchmark.pc.in file where libdir and includedir are always prefixed with prefix, even when they are absolute paths. The fix should check if the path is absolute before concatenating. Two approaches are referenced: using a helper function from cmake snips or the approach from KDE's extra cmake modules. The contributor should implement one of these and ensure the generated .pc file works correctly with absolute paths, such as on NixOS. No linked PRs or assignees.