Debugging OpenFAST

Being a Fortran project, OpenFAST can be challenging to debug and the process is unique for each system and environment. Keep in mind that some OpenFAST cases can be quite large in their memory footprint and may take a long time to reach the point of interest in the code. Choosing a test case carefully could save a significant amount time.

It may by helpful to write a small fortran program to verify that all debugging tools are set up properly before diving in to OpenFAST. Be sure to simulate a bug by doing something like accessing an array element that is not allocated and verify that you can catch the bug with a given set of tools.


A requirement for all systems is to compile OpenFAST in debug mode. Debugging on Windows

Windows developers using Intel tools can use Visual Studio solution included in the OpenFAST repository for debugging. This is a straightforward process with lots of support from Intel.

Otherwise, Windows developers compiling in Unix-style environments should proceed to Debugging on Linux and macOS. Debugging on Linux and macOS

First, compile OpenFAST in debug mode by setting CMAKE_BUILD_TYPE to “Debug”. This can be done on the command line with:

cmake .. -D CMAKE_BUILD_TYPE=Debug

or by using ccmake to open the command line cmake gui to change it.

The GNU debugger, gdb, works well for debugging compiled code. It has a comprehensive command line interface which enables developers to add breakpoints and inspect variables.

Driving the debugger through an IDE can make inspecting the code much more efficient. One IDE known to work well is Visual Studio Code with the Native Debug extension. You can set up a launch configuration so that you can debug a particular OpenFAST case through the IDE. To do this, open the launch configuration and add a block similar to this:

    "name": "AOC_WSt",
    "type": "gdb",
    "request": "launch",
    "printCalls": false,
    "showDevDebugOutput": false,
    "valuesFormatting": "prettyPrinters",
    "gdbpath": "gdb",
    "target": "${workspaceRoot}/build/glue-codes/openfast/openfast",
    "cwd": "${workspaceRoot}/build/reg_tests/glue-codes/openfast/AOC_WSt/",
    "arguments": "${workspaceRoot}/build/reg_tests/glue-codes/openfast/AOC_WSt/AOC_WSt.fst",
} macOS-specific configuration

GDB on macOS needs some configuration before the system allows it to take over a process. It is recommended that gdb be installed with homebrew

brew info gdb
brew install gdb

After that completes, be sure to follow the caveats to finish the installation. For gdb 8.2.1, it looks like this:

==> Caveats
gdb requires special privileges to access Mach ports.
You will need to codesign the binary. For instructions, see:


On 10.12 (Sierra) or later with SIP, you need to run this:

echo "set startup-with-shell off" >> ~/.gdbinit

For Native Debug on macOS, you have to sort of hack the extension to allow breakpoints in fortran files by adding this line to .vscode/settings.json:

    "debug.allowBreakpointsEverywhere": true