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How to fix Rust error: failed to run custom build command for

Problem

While building a Rust project, you encounter the following error:

example.txt
error: failed to run custom build command for `yeslogic-fontconfig-sys v6.0.0`

Caused by:
  process didn't exit successfully: `/home/uli/mkstatuslogs-rs/target/debug/build/yeslogic-fontconfig-sys-35b190da65259604/build-script-build` (exit status: 101)
  --- stdout
  cargo:rerun-if-env-changed=RUST_FONTCONFIG_DLOPEN
  cargo:rerun-if-env-changed=FONTCONFIG_NO_PKG_CONFIG
  cargo:rerun-if-env-changed=PKG_CONFIG_x86_64-unknown-linux-gnu
  cargo:rerun-if-env-changed=PKG_CONFIG_x86_64_unknown_linux_gnu
  cargo:rerun-if-env-changed=HOST_PKG_CONFIG
  cargo:rerun-if-env-changed=PKG_CONFIG
  cargo:rerun-if-env-changed=FONTCONFIG_STATIC
  cargo:rerun-if-env-changed=FONTCONFIG_DYNAMIC
  cargo:rerun-if-env-changed=PKG_CONFIG_ALL_STATIC
  cargo:rerun-if-env-changed=PKG_CONFIG_ALL_DYNAMIC
  cargo:rerun-if-env-changed=PKG_CONFIG_PATH_x86_64-unknown-linux-gnu
  cargo:rerun-if-env-changed=PKG_CONFIG_PATH_x86_64_unknown_linux_gnu
  cargo:rerun-if-env-changed=HOST_PKG_CONFIG_PATH
  cargo:rerun-if-env-changed=PKG_CONFIG_PATH
  cargo:rerun-if-env-changed=PKG_CONFIG_LIBDIR_x86_64-unknown-linux-gnu
  cargo:rerun-if-env-changed=PKG_CONFIG_LIBDIR_x86_64_unknown_linux_gnu
  cargo:rerun-if-env-changed=HOST_PKG_CONFIG_LIBDIR
  cargo:rerun-if-env-changed=PKG_CONFIG_LIBDIR
  cargo:rerun-if-env-changed=PKG_CONFIG_SYSROOT_DIR_x86_64-unknown-linux-gnu
  cargo:rerun-if-env-changed=PKG_CONFIG_SYSROOT_DIR_x86_64_unknown_linux_gnu
  cargo:rerun-if-env-changed=HOST_PKG_CONFIG_SYSROOT_DIR
  cargo:rerun-if-env-changed=PKG_CONFIG_SYSROOT_DIR

  --- stderr

  thread 'main' (3801409) panicked at /home/uli/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/yeslogic-fontconfig-sys-6.0.0/build.rs:8:48:
  called `Result::unwrap()` on an `Err` value: "\npkg-config exited with status code 1\n> PKG_CONFIG_ALLOW_SYSTEM_LIBS=1 PKG_CONFIG_ALLOW_SYSTEM_CFLAGS=1 pkg-config --libs --cflags fontconfig\n\npkg-config output:\n  Package fontconfig was not found in the pkg-config search path.\n  Perhaps you should add the directory containing `fontconfig.pc'\n  to the PKG_CONFIG_PATH environment variable\n  Package 'fontconfig', required by 'virtual:world', not found\n\nThe system library `fontconfig` required by crate `yeslogic-fontconfig-sys` was not found.\nThe file `fontconfig.pc` needs to be installed and the PKG_CONFIG_PATH environment variable must contain its parent directory.\nThe PKG_CONFIG_PATH environment variable is not set.\n\nHINT: if you have installed the library, try setting PKG_CONFIG_PATH to the directory containing `fontconfig.pc`.\n"
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
warning: build failed, waiting for other jobs to finish...

Solution

The error message indicates that the fontconfig library is missing from your system.

On Linux distributions such as Ubuntu, install it using

example.sh
sudo apt install libfontconfig-dev

Tested on Ubuntu 24.04 LTS

Check out similar posts by category: Rust, Linux