protocolbuffers/protobuf

pkg-config can not resolve dependencies

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#24610 opened on Nov 26, 2025

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cmakehelp wanted

Description

What version of protobuf and what language are you using? 33.0 Language: C++

What operating system (Linux, Windows, ...) and version? Linux (Ubunut)

What runtime / compiler are you using (e.g., python version or gcc version) clang 21

What did you do?

  1. build from source using CMake and install to any DIR
  2. set PKG_CONFIG_PATH to the DIR/lib/pkgconfig
  3. execute pkg-config protobuf --cflags or pkgconf protobuf --cflags
  4. Additional step is to execute pkgconf protobuf --digraph

What did you expect to see The output should be there within seconds The dependencies graphs should have a sane size

What did you see instead? pkg-config/pkgconf got stuck for minutes (I've been waiting for around 15) The graph is insanely large (>2 millions nodes)

I'm honestly not an expert with any of pkg-config or pkgconf, but to me it looks like some kind of cyclic dependencies somewhere in CMake files

Contributor guide

Tech stack
cpp
Domain
build systemtooling
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
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.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
familiarity with CMake
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30
Research direction
Investigate the CMake configuration files in the protobuf repository, specifically the .cmake files that generate pkg config (.pc) files. Look for potential cyclic dependencies or overly broad dependency lists that cause pkg config to generate an enormous dependency graph. Check the generated protobuf.pc file and the CMakeLists.txt that defines the library dependencies. Review any recent changes to the CMake configuration that might have introduced the cycle.