C++ CMake Build Issue with SQLite3 Fixed Using pkg-config Utility

Fix was released

When I ran find_package( SQLite3 REQUIRED ) in my CMake script three weeks ago, it failed and output an error. find_package is always a great help to solve dependencies and write portable build scripts with a small effort, thanks to the contributors who abstracted and automated the configurations and the version controls. While being familiar with such circumstances, I've been a bit too lazy and feeling annoyed by the need to write manual configuration when the utility fails.

While looking for solutions to this find_package problem with SQLite3, I found many people on the Internet suggesting different ways, but most of those didn't work for me. Then, I became interested in the source of this confusion.

When I reached the script FindSQLite3.cmake under the GitHub repository Kitware/CMake, I noticed that it looked different from the one I could see in my environment, which I had with CMake 3.29.6. Fortunately or unfortunately, it had already been fixed since 2024 March but was still waiting for the next release. Now, 3.30.0 was released last week with this fix. Let's upgrade CMake and enjoy the ease of building C++ code with SQLite3.

The fix in the script looks quite simple: using the pkg_check_modules command from the PkgConfig package. It calls the pkg-config tool to get the information compilers require and make it available in variables in CMake scripts. Check what variables you can get with it on the CMake documentation here.

Even if you cannot upgrade CMake right now but have or can install pkg-config, you can solve the issue using the tool by including the small script below in your CMake script. This solution was what I used for the time being.

find_package(PkgConfig)
pkg_check_modules(PC_SQLite3 sqlite3)
set( SQLite3_ROOT "${PC_SQLite3_PREFIX}" )

pkg-config is helpful

As pkg-config is a command-line tool, I became interested in how it can change the C++ code compilation on the command line. So, I gave it a go with the code from my last column.

# install pkg-config
apt-get install pkg-config
# install sqlite3 libraries
apt-get install libsqlite3-dev
# compile the code setting up compile options by pkg-config
g++ --std=c++14 -I./include ./main-2.cpp ./src/SmartDbConnFactory.cpp $(pkg-config --libs --cflags sqlite3)

The compile succeeded, and the built executable works!

However, executing pkg-config --libs --cflags sqlite3, I only get -lsqlite3. I couldn't feel the power of this tool from it.

So, I also tried it with OpenCV. This time, the command returned a long one. It's going to be interesting.

-I/usr/include/opencv4 -lopencv_stitching -lopencv_alphamat -lopencv_aruco -lopencv_barcode -lopencv_bgsegm -lopencv_bioinspired -lopencv_ccalib -lopencv_cvv -lopencv_dnn_objdetect -lopencv_dnn_superres -lopencv_dpm -lopencv_face -lopencv_freetype -lopencv_fuzzy -lopencv_hdf -lopencv_hfs -lopencv_img_hash -lopencv_intensity_transform -lopencv_line_descriptor -lopencv_mcc -lopencv_quality -lopencv_rapid -lopencv_reg -lopencv_rgbd -lopencv_saliency -lopencv_shape -lopencv_stereo -lopencv_structured_light -lopencv_phase_unwrapping -lopencv_superres -lopencv_optflow -lopencv_surface_matching -lopencv_tracking -lopencv_highgui -lopencv_datasets -lopencv_text -lopencv_plot -lopencv_ml -lopencv_videostab -lopencv_videoio -lopencv_viz -lopencv_wechat_qrcode -lopencv_ximgproc -lopencv_video -lopencv_xobjdetect -lopencv_objdetect -lopencv_calib3d -lopencv_imgcodecs -lopencv_features2d -lopencv_dnn -lopencv_flann -lopencv_xphoto -lopencv_photo -lopencv_imgproc -lopencv_core

Let's have a simple code with OpenCV. This program will convert an image file into a grayscale image.

// main.cpp
#include <iostream>
#include <opencv2/opencv.hpp>

int main() {
	cv::Mat image = cv::imread("example.jpg");
	cv::Mat grayImage;
	cv::cvtColor(image, grayImage, cv::COLOR_BGR2GRAY);
	cv::imwrite("example_gray.jpg", grayImage);
	return 0;
}

Now, compile it using pkg-config utility.

# install OpenCV libraries and dependencies
apt-get install libopencv-dev
# compile the code setting up compile options by pkg-config
g++ --std=c++14 main.cpp $(pkg-config --libs --cflags opencv4)

The compile was successful, and the image file conversion works! I'm excited about this result. It'll make my coding life easier.