build(meson): more robust python build

this option is useful for wheel builds

.gitignore

@@ -86,3 +86,4 @@ output/
 .idea/
 
 scratch/
+subprojects/.wraplock

cross/macos_arm64.ini

@@ -0,0 +1,19 @@
+[binaries]
+c = 'arm64-apple-darwin25-clang'
+cpp = 'arm64-apple-darwin25-clang++'
+ar = 'arm64-apple-darwin25-ar'
+strip = 'arm64-apple-darwin25-strip'
+pkg-config = 'pkg-config'
+ranlib = '/usr/bin/true'
+
+[host_machine]
+system = 'darwin'
+cpu_family = 'aarch64'
+cpu = 'arm64'
+endian = 'little'
+
+[built-in options]
+c_args = ['-mmacosx-version-min=15.0']
+cpp_args = ['-mmacos-version-min=15.0']
+c_link_args = ['-mmacosx-version-min=15.0']
+cpp_link_args = ['-mmacos-version-min=15.0']

cross/wasm.ini

@@ -0,0 +1,19 @@
+[binaries]
+cpp = 'em++'
+ar = 'emar'
+strip = 'emstrip'
+
+exec_wrapper = 'node'
+
+[built-in options]
+cpp_args = ['-Dpkg_config=false', '-Dbuild_tests=false', '-Dbuild_examples=true', '-fwasm-exceptions', '-s', 'MEMORY64=1']
+cpp_link_args = ['-s', 'WASM=1', '-s', 'ALLOW_MEMORY_GROWTH=1', '-s', 'MEMORY64=1', '-fwasm-exceptions']
+
+[host_machine]
+system = 'emscripten'
+cpu_family = 'wasm64'
+cpu = 'wasm64'
+endian = 'little'
+
+[properties]
+cmake_toolchain_file = '/home/tboudreaux/Programming/emsdk/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake'

examples/meson.build

@@ -0,0 +1 @@
+executable('simple_constant_usage', 'simple.cpp', dependencies: [const_dep])

examples/simple.cpp

@@ -0,0 +1,13 @@
+#include "fourdst/constants/const.h"
+#include <iostream>
+
+int main() {
+  fourdst::constant::Constants& C = fourdst::constant::Constants::getInstance();
+  
+  std::cout << "Speed of light is " << C.get("c") << std::endl;
+  std::cout << "All avalible constants are: ";
+
+  for (const auto& key : C.keys()) {
+    std::cout << "\t " << key << ": " << C[key];
+  }
+}

meson.build

@@ -18,26 +18,56 @@
 #   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 #
 # *********************************************************************** #
-project('libconstants', 'cpp', version: 'v1.0.6', default_options: ['cpp_std=c++23'], meson_version: '>=1.5.0')
+project('libconstants', 'cpp', version: 'v1.1.6', default_options: ['cpp_std=c++23'], meson_version: '>=1.5.0')
 
 # Add default visibility for all C++ targets
 add_project_arguments('-fvisibility=default', language: 'cpp')
 
+if get_option('build_python')
+    local_py_install = import('python').find_installation('python3', pure: false)
+    fourdst_pkg = local_py_install.get_install_dir() / 'fourdst'
+
+    constants_libdir             = fourdst_pkg / 'lib'
+    constants_header_install_dir = fourdst_pkg / 'include' / 'fourdst' / 'constants'
+
+    vendor_lib_dir             = fourdst_pkg / 'lib' / 'vendor'
+    vendor_header_dir          = fourdst_pkg / 'include' / 'fourdst' / 'vendor'
+
+    message('Installing libconfig in python mode. Install locations are...')
+else
+    constants_libdir             = get_option('libdir')
+    constants_header_install_dir = get_option('includedir') / 'fourdst' / 'constants'
+
+    message('Installing libconfig in non python (normal) mode. Install locations are...')
+endif
+message('    Libraries: ' + constants_libdir)
+message('    Headers:   ' + constants_header_install_dir)
+
+
 cpp = meson.get_compiler('cpp')
 
 subdir('assets/static')
 
 subdir('src')
-subdir('tests')
 
-pkg = import('pkgconfig')
-pkg.generate(
-    name: 'libconstants',
-    description: 'Physical Constants for SERiF and related projects',
-    version: meson.project_version(),
-    libraries: [libconst],
-    subdirs: ['fourdst'],
-    filebase: 'fourdst_constants',
-    install_dir: join_paths(get_option('libdir'), 'pkgconfig')
-)
+if get_option('build_tests')
+  subdir('tests')
+endif
+
+if get_option('build_examples')
+  subdir('examples')
+endif
+
+if get_option('pkg_config')
+    message('Generating pkg-config file for libconstants...')
+    pkg = import('pkgconfig')
+    pkg.generate(
+        name: 'libconstants',
+        description: 'Physical Constants for SERiF and related projects',
+        version: meson.project_version(),
+        libraries: [libconst, '-Wl,-rpath,${libdir}'],
+        filebase: 'fourdst_constants',
+        install_dir: join_paths(get_option('libdir'), 'pkgconfig')
+    )
+endif
 

meson_options.txt

@@ -0,0 +1,4 @@
+option('pkg_config', type: 'boolean', value: true, description: 'generate pkg-config file for libconstants (fourdst_constants.pc)')
+option('build_tests', type: 'boolean', value: true, description: 'control if tests are built or not')
+option('build_examples', type: 'boolean', value: true, description: 'control if examples is built or not')
+option('build_python', type: 'boolean', value: false, description: 'Build in python mode. Note that this does not generate a wheel; rather, this is the appropriate option to turn on when packaging this component inside of a wheel.')

src/constants/lib/const.cpp

@@ -20,11 +20,10 @@
 // *********************************************************************** */
 #include <iostream>
 #include <map>
-#include <vector>
 #include <string>
-#include <fstream>
 #include <sstream>
 #include <set>
+#include <exception>
 
 
 #include "fourdst/constants/const.h"

src/constants/meson.build

@@ -10,7 +10,8 @@ libconst = library('const',
     include_directories: include_directories('include'),
     cpp_args: ['-fvisibility=default'],
     dependencies: [const_data_dep],
-    install : true)
+    install : true,
+    install_dir: constants_libdir)
 
 const_dep = declare_dependency(
     include_directories: include_directories('include'),
@@ -21,4 +22,5 @@ const_dep = declare_dependency(
 const_headers = files(
   'include/fourdst/constants/const.h'
 )
-install_headers(const_headers, subdir : 'fourdst/fourdst/constants')
+
+install_headers(const_headers, install_dir: constants_header_install_dir)