SwiftPM build/run error due to missing `pkg-config`

Using Swift
1

I am trying to build a small command line executable using the recently introduced Benchmark Package.

I can build and run the binary in my package after I have added the dependency on the benchmark package:

swift run -c release
warning: failed to retrieve search paths with pkg-config; maybe pkg-config is not installed
warning: you may be able to install jemalloc using your system-packager:
    brew install jemalloc
Building for production...
[4/4] Linking bm1
Build of product 'bm1' complete! (4.63s)
Hello, Swift!

but what about these warning about pkg-config missing?

Despite the above working, when I try and run the benchmarks I get an error:

% swift package benchmark
warning: failed to retrieve search paths with pkg-config; maybe pkg-config is not installed
warning: you may be able to install jemalloc using your system-packager:
    brew install jemalloc
Building for debugging...
<module-includes>:1:9: note: in file included from <module-includes>:1:
1 | #import "../../Headers/jemalloc.h"
  |         `- note: in file included from <module-includes>:1:
2 |

/Users/giik/Developer/CLI/BMPackage1/.build/checkouts/package-jemalloc/Sources/jemalloc/../../Headers/jemalloc.h:1:10: error: 'jemalloc/jemalloc.h' file not found
1 | #include <jemalloc/jemalloc.h>
  |          `- error: 'jemalloc/jemalloc.h' file not found

What is pkg-config? Is it something my system was already supposed to have (this is on MacOS 15 with Xcode and the tools installed, and so far I haven't had any issues depending on packages in Xcode or in CL tools using the SwiftPM)?

I have only

% pkg
pkgbuild  pkgutil

and looking around I found pkgconf on homebrew. Does SwiftPM expect to find this on my machine? If yes, why did it not come with SwiftPM or the developer tools, etc.? I searched the SwiftPM documentation quickly but did not find any mention of pkg-config.

I'd install it if I have to but wanted to make sure I am not doing something wrong/missing some config somewhere.

2

You're getting a warning about pkg-config, not an error. The error in question is because you don't have jemalloc installed on your machine, which is understandable because I also had this error when using the benchmark package for the first time and installing it fixed the problem.

3

Yeah, I fixed it by installing jemalloc. I think I was confused because I expecting that all dependencies of the benchmark package will be pulled automatically.

4

The Benchmark package declares a dependency on a jemalloc Package (github.com/ordo-one/package-jemalloc. This package in turn declares a target "jemalloc" as a .systemLibrary:

    targets: [
        .systemLibrary(
            name: "jemalloc",
            pkgConfig: "jemalloc",
            providers: [
                .brew(["jemalloc"])
            ]
        ),
    ]

The .systemLibrary type is used in SwiftPM to designate libraries that are expected to be installed globally on the system. SwiftPM won't ever install a system library; it expects it to exist in one of the standard include and library paths for your system.

pkg-config is a tool that builds a local database of system libraries and where to find the header and dylib files for those. If pkg-config is installed on your system, SwiftPM will query the pkg-config database to find the include and library search paths for any system library targets declared by a package. It's optional, though, because SwiftPM will always fall back on the default include and library search paths that make sense for your system, I believe.

I don't think pkg-config is installed by default on macOS, but you can install it via Homebrew with brew install pkgconf (which you have already found).

On my machine, I can run e.g. these commands to find out how to compile and link against jemalloc (also installed via Homebrew):

$ pkg-config --cflags jemalloc
-I/opt/homebrew/Cellar/jemalloc/5.3.0/include
$ pkg-config --libs jemalloc
-L/opt/homebrew/Cellar/jemalloc/5.3.0/lib -ljemalloc

I imagine SwiftPM does something similar internally.