Compilers and libraries - OpenMC Workbench

A few notes on the compilers and libraries used by the C++ examples. The Linux instructions cover Debian, Ubuntu, and Red Hat Enterprise Linux (RHEL), followed by macOS. The examples use C++23, although they do not necessarily rely on C++23-specific features.

Linux (Debian, Ubuntu, and Red Hat)¶

C++ compilers¶

GCC is a straightforward choice for compiling the examples. Install the usual build tools if needed.

Debian or Ubuntu:

sudo apt install build-essential

Red Hat Enterprise Linux:

sudo dnf group install "Development Tools"

Check which compiler is being used:

which g++
g++ --version

Clang is another option if installed:

which clang++
clang++ --version

For an example that uses no additional libraries:

g++ -std=c++23 example.cpp -o example

The available C++23 features depend on the compiler and its standard library. In particular, RHEL 9’s system GCC is older; a newer GCC Toolset may be needed for -std=c++23 and newer language features.

HDF5¶

HDF5 includes h5c++, a wrapper that supplies the compiler and linking options needed by its C++ interface.

Debian or Ubuntu:

sudo apt install libhdf5-dev

Red Hat Enterprise Linux:

sudo dnf install hdf5-devel

On RHEL 9, hdf5-devel is available through EPEL, which may need to be enabled first (see Red Hat’s EPEL setup guidance).

Inspect the installed wrapper:

which h5c++
h5c++ -show
h5c++ -showconfig

which h5c++ shows which installation is being used.
h5c++ -show prints the underlying compiler command, including include paths and libraries.
h5c++ -showconfig reports the HDF5 build configuration.

Compile the HDF5 example with:

h5c++ -std=c++23 inspect_hdf5.cpp -o inspect_hdf5

The wrapper may use GCC or another compiler, depending on how HDF5 was built. Check -show rather than assuming.

XML and pugixml¶

The XML example uses pugixml. Install its development package.

Debian or Ubuntu:

sudo apt install libpugixml-dev

Red Hat Enterprise Linux:

sudo dnf install pugixml-devel

On RHEL 9, pugixml-devel is available through EPEL.

Then compile with:

g++ -std=c++23 inspect_xml.cpp -o inspect_xml -lpugixml

These packages install headers and libraries in standard system locations, so extra -I and -L options are normally unnecessary.

macOS¶

C++ compilers¶

Apple Clang is available through Xcode or Apple’s command-line developer tools. To inspect the compiler selected by those tools:

xcrun --find clang++
xcrun clang++ --version

MacPorts can also provide GCC, with versioned executable names. For GCC 15:

which g++-mp-15
g++-mp-15 --version

A Conda environment may provide another Clang compiler. Check the executable name shown by a library’s compiler wrapper; in one openmc-env installation, h5c++ -show uses arm64-apple-darwin20.0.0-clang++.

For a standalone C++ example using Apple Clang:

clang++ -std=c++23 example.cpp -o example

HDF5¶

In the openmc-env Conda environment, HDF5 provides h5c++. Activate the environment and inspect the wrapper:

conda activate openmc-env
which h5c++
h5c++ -show
h5c++ -showconfig

Here, h5c++ -show identifies the Conda compiler and the HDF5 libraries and paths supplied automatically. The precise flags depend on the environment; there is no need to copy them into the build command.

Compile the HDF5 example with:

h5c++ -std=c++23 inspect_hdf5.cpp -o inspect_hdf5

h5c++ is a compiler wrapper, not a separate C++ compiler. Its underlying compiler may differ from the one returned by which clang++.

XML and pugixml¶

In this macOS setup, pugixml is installed through MacPorts. Check the installation:

port installed pugixml

Compile the XML example with Apple Clang:

clang++ -std=c++23 inspect_xml.cpp -o inspect_xml \
    -I/opt/local/include -L/opt/local/lib -lpugixml

Here:

-I/opt/local/include gives the compiler the location of pugixml.hpp.
-L/opt/local/lib gives the linker the library directory.
-lpugixml links the pugixml library.

An error about a missing pugixml.hpp usually indicates an include-path issue. Undefined pugixml symbols at link time usually indicate a missing or incorrect library option.

The HDF5 and pugixml examples use different installations here—Conda for HDF5 and MacPorts for pugixml—so their build commands are kept separate.