From c7d18c16259048878ab566c30aea2078a94b58fe Mon Sep 17 00:00:00 2001
From: Palmer Dabbelt <palmer@dabbelt.com>
Date: Thu, 8 Aug 2019 14:36:27 -0700
Subject: [PATCH 1/2] cmake: Generate and install a pkg-config file.

The meson builds install a pkg-config file, but the cmake builds don't.
This adds a pkg-config file to the cmake builds that is functionally
equivalent to the one generated from meson.
---
 CMakeLists.txt         | 12 +++++++++++-
 cmake/pkg-config.pc.in |  4 ++++
 2 files changed, 15 insertions(+), 1 deletion(-)
 create mode 100644 cmake/pkg-config.pc.in

diff --git a/CMakeLists.txt b/CMakeLists.txt
index f7ba4fa3..372a7a03 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -4,7 +4,7 @@ cmake_minimum_required(VERSION 3.1)
 ## PROJECT
 ## name and version
 ##
-project(nlohmann_json VERSION 3.8.0 LANGUAGES CXX)
+project(nlohmann_json VERSION 3.8.0 DESCRIPTION "JSON for Modern C++" LANGUAGES CXX)
 
 ##
 ## INCLUDE
@@ -79,6 +79,12 @@ if (MSVC)
     )
 endif()
 
+# Install a pkg-config file, so other tools can find this.
+CONFIGURE_FILE(
+  "${CMAKE_CURRENT_SOURCE_DIR}/cmake/pkg-config.pc.in"
+  "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}.pc"
+)
+
 ##
 ## TESTS
 ## create and configure the unit test target
@@ -139,4 +145,8 @@ endif()
         NAMESPACE ${PROJECT_NAME}::
         DESTINATION ${NLOHMANN_JSON_CONFIG_INSTALL_DIR}
     )
+    install(
+        FILES "${CMAKE_BINARY_DIR}/${PROJECT_NAME}.pc"
+        DESTINATION lib/pkgconfig
+    )
 endif()
diff --git a/cmake/pkg-config.pc.in b/cmake/pkg-config.pc.in
new file mode 100644
index 00000000..680f10c2
--- /dev/null
+++ b/cmake/pkg-config.pc.in
@@ -0,0 +1,4 @@
+Name: ${PROJECT_NAME}
+Description: ${PROJECT_DESCRIPTION}
+Version: ${PROJECT_VERSION}
+Cflags: -I${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_INCLUDEDIR}

From 251fce819c64b356d039f1777740ab9c0489d495 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=89rico=20Rolim?= <erico.erc@gmail.com>
Date: Wed, 8 Jul 2020 17:10:51 -0300
Subject: [PATCH 2/2] README: add explanation on how to use pkg-config.

---
 README.md | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/README.md b/README.md
index 3bb92d38..41d3145c 100644
--- a/README.md
+++ b/README.md
@@ -27,6 +27,7 @@
 - [Integration](#integration)
   - [CMake](#cmake)
   - [Package Managers](#package-managers)
+  - [Pkg-config](#pkg-config)
 - [Examples](#examples)
   - [JSON as first-class data type](#json-as-first-class-data-type)
   - [Serialization / Deserialization](#serialization--deserialization)
@@ -230,6 +231,20 @@ Please file issues [here](https://github.com/build2-packaging/nlohmann-json) if
 
 If you are using [`wsjcpp`](https://wsjcpp.org), you can use the command `wsjcpp install "https://github.com/nlohmann/json:develop"` to get the latest version. Note you can change the branch ":develop" to an existing tag or another branch.
 
+### Pkg-config
+
+If you are using bare Makefiles, you can use `pkg-config` to generate the include flags that point to where the library is installed:
+
+```sh
+pkg-config nlohmann_json --cflags
+```
+
+Users of the Meson build system will also be able to use a system wide library, which will be found by `pkg-config`:
+
+```meson
+json = dependency('nlohmann_json', required: true)
+```
+
 ## Examples
 
 Beside the examples below, you may want to check the [documentation](https://nlohmann.github.io/json/) where each function contains a separate code example (e.g., check out [`emplace()`](https://nlohmann.github.io/json/classnlohmann_1_1basic__json_a5338e282d1d02bed389d852dd670d98d.html#a5338e282d1d02bed389d852dd670d98d)). All [example files](https://github.com/nlohmann/json/tree/develop/doc/examples) can be compiled and executed on their own (e.g., file [emplace.cpp](https://github.com/nlohmann/json/blob/develop/doc/examples/emplace.cpp)).