From d89f8f2ed29bb8355a8aff8da3ff78b9ed1b5604 Mon Sep 17 00:00:00 2001
From: Radonirinaunimi <rrabeman@nikhef.nl>
Date: Thu, 5 Mar 2026 16:06:27 +0100
Subject: [PATCH 1/3] Add a `build.rs` to automatically install the OOP C++
 header

---
 .github/workflows/capi.yaml                   |  1 +
 examples/object-oriented-cpp/dyaa.cpp         |  4 ++--
 pineappl_capi/build.rs                        | 21 +++++++++++++++++++
 .../src/include}/PineAPPL.hpp                 |  0
 4 files changed, 24 insertions(+), 2 deletions(-)
 create mode 100644 pineappl_capi/build.rs
 rename {examples/object-oriented-cpp => pineappl_capi/src/include}/PineAPPL.hpp (100%)

diff --git a/.github/workflows/capi.yaml b/.github/workflows/capi.yaml
index 518c143e..9fe83f55 100644
--- a/.github/workflows/capi.yaml
+++ b/.github/workflows/capi.yaml
@@ -26,6 +26,7 @@ jobs:
           RUSTFLAGS: '-Cinstrument-coverage -Clink-dead-code'
         run: |
           cd pineappl_capi
+          export PINEAPPL_C_INSTALL_PREFIX=/usr/local
           cargo cinstall --verbose --prefix=/usr/local/ --libdir=/usr/local/lib
           ldconfig
 
diff --git a/examples/object-oriented-cpp/dyaa.cpp b/examples/object-oriented-cpp/dyaa.cpp
index bdffc142..58ceceac 100644
--- a/examples/object-oriented-cpp/dyaa.cpp
+++ b/examples/object-oriented-cpp/dyaa.cpp
@@ -8,8 +8,8 @@
 #include <random>
 #include <vector>
 
-#include "PineAPPL.hpp"
-#include "pineappl_capi.h"
+#include <PineAPPL.hpp>
+#include <pineappl_capi.h>
 
 double int_photo(double s, double t, double u) {
   double alpha0 = 1.0 / 137.03599911;
diff --git a/pineappl_capi/build.rs b/pineappl_capi/build.rs
new file mode 100644
index 00000000..c39e6025
--- /dev/null
+++ b/pineappl_capi/build.rs
@@ -0,0 +1,21 @@
+//! A build script to install the OOP C++ interface to `PineAPPL`.
+
+use std::env;
+use std::fs;
+use std::path::PathBuf;
+
+fn main() {
+    println!("cargo:rerun-if-changed=src/include/PineAPPL.hpp");
+
+    if let Ok(prefix) = env::var("PINEAPPL_C_INSTALL_PREFIX") {
+        let prefix_path = PathBuf::from(prefix);
+        let include_path = prefix_path.join("include").join("pineappl_capi");
+
+        fs::create_dir_all(&include_path).expect("Failed to create include directory.");
+
+        let source_header = PathBuf::from("src/include/PineAPPL.hpp");
+        let dest_header = include_path.join("PineAPPL.hpp");
+
+        fs::copy(&source_header, &dest_header).expect("Failed to copy header file.");
+    }
+}
diff --git a/examples/object-oriented-cpp/PineAPPL.hpp b/pineappl_capi/src/include/PineAPPL.hpp
similarity index 100%
rename from examples/object-oriented-cpp/PineAPPL.hpp
rename to pineappl_capi/src/include/PineAPPL.hpp

From 29f23eec511dcd13cadbc2ec8f6a13ed4325de34 Mon Sep 17 00:00:00 2001
From: Radonirinaunimi <rrabeman@nikhef.nl>
Date: Thu, 5 Mar 2026 16:09:57 +0100
Subject: [PATCH 2/3] Adjust the C/C++-API release

---
 .github/workflows/release.yml | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index b6e15609..d36bdb7f 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -36,6 +36,7 @@ jobs:
           curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --target=${{ matrix.target }}
           cargo install --locked cargo-c
           cd pineappl_capi
+          export PINEAPPL_C_INSTALL_PREFIX=$(pwd)/prefix
           cargo cinstall --destdir=prefix --libdir=lib --library-type=cdylib --locked --prefix=/ --target=${{ matrix.target }} --verbose
           cd prefix
           tar czf ../../pineappl_capi-${{ matrix.target }}.tar.gz .
@@ -105,6 +106,7 @@ jobs:
       - name: Compile library
         run: |
           cd pineappl_capi
+          export PINEAPPL_C_INSTALL_PREFIX=$(pwd)/prefix
           cargo cinstall --destdir=prefix --libdir=lib --library-type=cdylib --locked --prefix=/ --target=${{ matrix.target }} --verbose
           cd prefix
           tar czf ../../pineappl_capi-${{ matrix.target }}.tar.gz .

From 69096fdf23b070e24877cf3be4df772ef8fde406 Mon Sep 17 00:00:00 2001
From: Radonirinaunimi <rrabeman@nikhef.nl>
Date: Fri, 6 Mar 2026 13:54:18 +0100
Subject: [PATCH 3/3] Document `PINEAPPL_C_INSTALL_PREFIX`

---
 docs/installation.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/docs/installation.md b/docs/installation.md
index 7d2f303a..e20f1838 100644
--- a/docs/installation.md
+++ b/docs/installation.md
@@ -75,6 +75,7 @@ If you want to build the CAPI from its sources instead, you first need to
 3. Now install `pineappl_capi`, PineAPPL's C API:
 
        cd pineappl_capi
+       export PINEAPPL_C_INSTALL_PREFIX=${prefix} # To copy the OOP C++ header
        cargo cinstall --release --prefix=${prefix} --libdir=${prefix}/lib
        cd ..