03_wmake

0. Preface

Having understood the Make-based implementation of C++ projects, we can now more easily grasp the wmake implementation approach provided by OpenFOAM.

This section primarily covers:

• A brief understanding of wmake
• Direct linking using wmake
• Dynamic library linking using wmake
• Understanding Make
• Compiling and running a wmake-based project

1. Understanding wmake

wmake in OpenFOAM is a build tool based on make. Essentially, it is a set of scripts and configuration files specifically designed for OpenFOAM projects. It simplifies the compilation process of OpenFOAM and automatically handles certain dependencies and path settings.

1. wmake is a wrapper script around make that sets up the environment variables and rules required for OpenFOAM compilation.
2. wmake automatically locates OpenFOAM’s specific directory structure and sets corresponding compilation options (such as include paths, library paths, etc.).
3. wmake provides an interface similar to make but is optimized for OpenFOAM.

OpenFOAM uses Make/files and Make/options to manage compilation with wmake.

OpenFOAM convention uses .C as the suffix for source files and .H for header files.

To avoid confusion regarding file structure, a loose distinction is made here. OpenFOAM’s project-level .H files are often used merely to split the main source code by functionality, facilitating code reading and maintenance; many of these are not class header files. This differs from class header files at the C++ development level and from source-level header files in OpenFOAM (e.g., $FOAM_SRC/OpenFOAM/dimensionSet/dimensionSet.H).

The following discussion focuses on simple source-level header files.

2. Project

Run the following commands in the terminal to create the project for this section:

ofsp
mkdir ofsp_03_wmake
code ofsp_03_wmake

Continue using terminal commands or the VS Code interface to create additional files. The final file structure is as follows:

tree
.
├── Aerosand
│   ├── Aerosand.C
│   └── Aerosand.H
├── Make
│   ├── files
│   └── options
└── ofsp_03_wmake.C

The declaration of the Aerosand library in Aerosand.H is as follows:

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#pragma once

class Aerosand
{
public:
    void SetLocalTime(double t);
    double GetLocalTime() const;


private:
    double localTime_;
};

The definition of the Aerosand library in Aerosand.C is as follows:

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#include "Aerosand.H"

void Aerosand::SetLocalTime(double t) {
    localTime_ = t;
}

double Aerosand::GetLocalTime() const {
    return localTime_;
}

The main application source file ofsp_03_wmake.C is as follows:

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#include <iostream>

#include "Aerosand.H"

using namespace std;

int main()
{
    int a = 1;
    double pi = 3.1415926;

    cout << "Hi, OpenFOAM!" << " Here we are." << endl;
    cout << a << " + " << pi << " = " << a + pi << endl;
    cout << a << " * " << pi << " = " << a * pi << endl;


    Aerosand mySolver;
    mySolver.SetLocalTime(0.2);
    cout << "\nCurrent time step is : " << mySolver.GetLocalTime() << endl;

    return 0;
}

OpenFOAM provides Make to assist development, where:

• The /Make/files file specifies the source files to compile and the name and location of the target to generate.
• The /Make/options file specifies compilation and linking options, including header file paths and libraries to link.

Note that #include "Aerosand.H" does not require a path specification because the path will be handled in the Make.

The following sections discuss different linking approaches and the details of the Make.

3. Direct Linking

Similar to the direct linking discussed in 02_helloWorld/3.4. Linking, this can also be achieved in OpenFOAM.

3.1. Configuring Make

The contents of ofsp_03_wmake/Make/files are as follows:

Aerosand/Aerosand.C
ofsp_03_wmake.C

EXE = $(FOAM_USER_APPBIN)/ofsp_00_helloWorld_wmake

• The source files are Aerosand.C and ofsp_03_wmake.C.
• The location of the generated target is $(FOAM_USER_APPBIN).
• The name of the generated target is ofsp_03_wmake.

The contents of ofsp_03_wmake/Make/options are as follows:

EXE_INC = \
	-IAerosand

EXE_LIBS = \

• The prefix EXE indicates that this configuration is for an executable (the prefix LIB indicates configuration for a library).
• The suffix INC denotes include paths.
  • The -I flag specifies header file search paths.
  • Typically points to the lnInclude directory of an OpenFOAM module (linked include directory).
  • Can include system header paths or third-party library header paths.
• The suffix LIBS denotes library linking (for direct linking, no libraries need to be linked; this can be left blank).
  • The -l flag specifies libraries to link.
  • Library names omit the lib prefix and .so suffix (e.g., -lfiniteVolume corresponds to libfiniteVolume.so).
  • The -L flag specifies library search paths.

Run the following command in the terminal to compile:

wclean
wmake

3.2. Compilation

The terminal output consists of three sections, corresponding to the three stages of application compilation.

The first section is the compilation of the custom Aerosand class, producing the object file Aerosand.o (see the end of the output):

g++ -std=c++14 -m64 -pthread -DOPENFOAM=2406 -DWM_DP -DWM_LABEL_SIZE=32 -Wall 
-Wextra -Wold-style-cast -Wnon-virtual-dtor -Wno-unused-parameter -Wno-invalid
-offsetof -Wno-attributes -Wno-unknown-pragmas -O3  -DNoRepository -ftemplate
-depth-100  -IAerosand -iquote. -IlnInclude 
-I/usr/lib/openfoam/openfoam2406/src/OpenFOAM/lnInclude 
-I/usr/lib/openfoam/openfoam2406/src/OSspecific/POSIX/lnInclude   -fPIC 
-c Aerosand/Aerosand.C -o Make/linux64GccDPInt32Opt/Aerosand/Aerosand.o

The second section is the compilation of the main source file, producing the object file ofsp_03_wmake.o (see the end of the output):

g++ -std=c++14 -m64 -pthread -DOPENFOAM=2406 -DWM_DP -DWM_LABEL_SIZE=32 -Wall 
-Wextra -Wold-style-cast -Wnon-virtual-dtor -Wno-unused-parameter -Wno-invalid
-offsetof -Wno-attributes -Wno-unknown-pragmas -O3  -DNoRepository -ftemplate
-depth-100  -IAerosand -iquote. -IlnInclude 
-I/usr/lib/openfoam/openfoam2406/src/OpenFOAM/lnInclude 
-I/usr/lib/openfoam/openfoam2406/src/OSspecific/POSIX/lnInclude   -fPIC 
-c ofsp_03_wmake.C -o Make/linux64GccDPInt32Opt/ofsp_03_wmake.o

The third section is the linking stage, where the two object files are directly linked to produce the final executable (see the end of the output):

g++ -std=c++14 -m64 -pthread -DOPENFOAM=2406 -DWM_DP -DWM_LABEL_SIZE=32 -Wall 
-Wextra -Wold-style-cast -Wnon-virtual-dtor -Wno-unused-parameter -Wno-invalid
-offsetof -Wno-attributes -Wno-unknown-pragmas -O3  -DNoRepository -ftemplate
-depth-100  -IAerosand -iquote. -IlnInclude 
-I/usr/lib/openfoam/openfoam2406/src/OpenFOAM/lnInclude 
-I/usr/lib/openfoam/openfoam2406/src/OSspecific/POSIX/lnInclude   
-fPIC -Xlinker --add-needed -Xlinker --no-as-needed
Make/linux64GccDPInt32Opt/Aerosand/Aerosand.o 
Make/linux64GccDPInt32Opt/ofsp_03_wmake.o 
-L/usr/lib/openfoam/openfoam2406/platforms/linux64GccDPInt32Opt/lib \
     -lOpenFOAM -ldl  \
     -lm -o /home/aerosand/OpenFOAM/aerosand
 -v2406/platforms/linux64GccDPInt32Opt/bin/ofsp_03_wmake

The intermediate build files are located in ofsp_03_wmake/Make/linux64GccDPInt32Opt/ (the exact path may vary depending on the platform). The generated executable is placed in the $FOAM_USER_APPBIN directory (as specified in Make/files).

Run the following command in the terminal to locate all successfully generated executables:

tree $FOAM_USER_APPBIN

3.3. Running

This executable is a standalone program that does not require any external files for input parameters. Thanks to OpenFOAM’s environment variables, the compiled program can be run directly from the terminal in any directory.

Run the following command in the terminal:

ofsp_03_wmake

The output is as follows:

Hi, OpenFOAM! Here we are.
1 + 3.14159 = 4.14159
1 * 3.14159 = 3.14159

Current time step is : 0.2

4. Dynamic Library Linking

In practical development, we still use dynamic libraries to ensure memory efficiency and performance.

Adjust the file structure as follows:

.
├── Aerosand
│   ├── Aerosand.C
│   ├── Aerosand.H
│   └── Make
│       ├── files
│       └── options
├── Make
│   ├── files
│   └── options
└── ofsp_03_wmake.C

4.1. Library Make

Create a Make for the library.

The contents of /Aerosand/Make/files are as follows:

Aerosand.C

LIB = $(FOAM_USER_LIBBIN)/libAerosand

• Note that LIB is used instead of EXE for a library.
• The target path ends with LIBBIN instead of APPBIN.
• The target file must be prefixed with lib.

Since this Aerosand library does not require linking with any other libraries, /Aerosand/Make/options can be left empty.

Run the following command in the terminal to compile the library from the root directory:

wmake Aerosand

The terminal output consists of two sections, corresponding to the compilation stages.

The first section compiles the custom Aerosand library, producing the object file Aerosand.o (see the end of the output):

g++ -std=c++14 -m64 -pthread -DOPENFOAM=2406 -DWM_DP -DWM_LABEL_SIZE=32 -Wall 
-Wextra -Wold-style-cast -Wnon-virtual-dtor -Wno-unused-parameter -Wno-invalid
-offsetof -Wno-attributes -Wno-unknown-pragmas -O3  -DNoRepository -ftemplate
-depth-100   -iquote. -IlnInclude 
-I/usr/lib/openfoam/openfoam2406/src/OpenFOAM/lnInclude 
-I/usr/lib/openfoam/openfoam2406/src/OSspecific/POSIX/lnInclude   -fPIC 
-c Aerosand.C -o Make/linux64GccDPInt32Opt/Aerosand.o

The second section links the object file Aerosand.o into a dynamic library Aerosand.so (see the end of the output):

g++ -std=c++14 -m64 -pthread -DOPENFOAM=2406 -DWM_DP -DWM_LABEL_SIZE=32 -Wall 
-Wextra -Wold-style-cast -Wnon-virtual-dtor -Wno-unused-parameter -Wno-invalid
-offsetof -Wno-attributes -Wno-unknown-pragmas -O3  -DNoRepository -ftemplate
-depth-100   -iquote. -IlnInclude 
-I/usr/lib/openfoam/openfoam2406/src/OpenFOAM/lnInclude 
-I/usr/lib/openfoam/openfoam2406/src/OSspecific/POSIX/lnInclude   -fPIC -shared 
-Xlinker --add-needed -Xlinker 
--no-as-needed  Make/linux64GccDPInt32Opt/Aerosand.o 
-L/usr/lib/openfoam/openfoam2406/platforms/linux64GccDPInt32Opt/lib \
      -o /home/aerosand/OpenFOAM/aerosand
-v2406/platforms/linux64GccDPInt32Opt/lib/libAerosand.so

The intermediate build files are located in ofsp_03_wmake/Aerosand/Make/linux64GccDPInt32Opt/ (the exact path may vary depending on the platform). The generated dynamic library is placed in the $FOAM_USER_LIBBIN directory (as specified in Make/files).

Run the following command in the terminal to locate all successfully generated dynamic libraries:

tree $FOAM_USER_LIBBIN

A library may contain multiple classes or even other sub-libraries. After compilation, an lnInclude folder is generated in the library’s path. This folder contains symbolic links to the declarations (.H files) and implementations (.C files) of all classes (or sub-libraries) within the library, providing a unified and simplified path for subsequent linking. For reference, examine the $FOAM_SRC/OpenFOAM library in OpenFOAM, where the lnInclude folder contains shortcuts to all classes (or sub-libraries) within that library.

Run the following command to view the file structure of the compiled Aerosand library:

Aerosand
├── Aerosand.C
├── Aerosand.H
├── lnInclude
│   ├── Aerosand.C -> ../Aerosand.C
│   └── Aerosand.H -> ../Aerosand.H
└── Make
    ├── files
    ├── linux64GccDPInt32Opt
    │   ├── Aerosand.C.dep
    │   ├── Aerosand.o
    │   ├── options
    │   ├── sourceFiles
    │   └── variables
    └── options

4.2. Project Make

Because the Aerosand library has been compiled into a dynamic library, we need to specify it in the project’s Make.

Modify /Make/files as follows:

ofsp_03_wmake.C

EXE = $(FOAM_USER_APPBIN)/ofsp_03_wmake

Modify /Make/options as follows:

EXE_INC = \
    -IAerosand/lnInclude

EXE_LIBS = \
    -L$(FOAM_USER_LIBBIN) \
    -lAerosand

• The prefix EXE indicates that this configuration is for an executable (the prefix LIB indicates configuration for a library).
• The suffix INC denotes include paths.
  • The -I flag specifies header file search paths.
  • Typically points to the lnInclude directory of an OpenFOAM module (linked include directory).
  • Can include system header paths or third-party library header paths.
• The suffix LIBS denotes library linking.
  • The -l flag specifies libraries to link.
  • Library names omit the lib prefix and .so suffix (e.g., -lAerosand corresponds to libAerosand.so).
  • The -L flag specifies library search paths.
• Ensure the file ends with a blank line to avoid OpenFOAM compilation warnings.

4.3. Compilation

Run the following command in the terminal to perform the compilation:

wclean
wmake

The terminal output consists of two sections, corresponding to the compilation stages.

The first section compiles the main source file, producing the object file ofsp_03_wmake.o (see the end of the output):

g++ -std=c++14 -m64 -pthread -DOPENFOAM=2406 -DWM_DP -DWM_LABEL_SIZE=32 -Wall 
-Wextra -Wold-style-cast -Wnon-virtual-dtor -Wno-unused-parameter -Wno-invalid
-offsetof -Wno-attributes -Wno-unknown-pragmas -O3  -DNoRepository -ftemplate
-depth-100  -IAerosand/lnInclude -iquote. -IlnInclude 
-I/usr/lib/openfoam/openfoam2406/src/OpenFOAM/lnInclude 
-I/usr/lib/openfoam/openfoam2406/src/OSspecific/POSIX/lnInclude   -fPIC 
-c ofsp_03_wmake.C -o Make/linux64GccDPInt32Opt/ofsp_03_wmake.o

The second section links the dynamic library to the application and generates the executable ofsp_03_wmake (see the end of the output):

g++ -std=c++14 -m64 -pthread -DOPENFOAM=2406 -DWM_DP -DWM_LABEL_SIZE=32 -Wall 
-Wextra -Wold-style-cast -Wnon-virtual-dtor -Wno-unused-parameter -Wno-invalid
-offsetof -Wno-attributes -Wno-unknown-pragmas -O3  -DNoRepository -ftemplate
-depth-100  -IAerosand/lnInclude -iquote. -IlnInclude 
-I/usr/lib/openfoam/openfoam2406/src/OpenFOAM/lnInclude 
-I/usr/lib/openfoam/openfoam2406/src/OSspecific/POSIX/lnInclude   -fPIC -Xlinker
--add-needed -Xlinker --no-as-needed  Make/linux64GccDPInt32Opt/ofsp_03_wmake.o 
-L/usr/lib/openfoam/openfoam2406/platforms/linux64GccDPInt32Opt/lib \
    -L/home/aerosand/OpenFOAM/aerosand-v2406/platforms/linux64GccDPInt32Opt/lib 
    -lAerosand -lOpenFOAM -ldl  \
     -lm -o /home/aerosand/OpenFOAM/aerosand
-v2406/platforms/linux64GccDPInt32Opt/bin/ofsp_03_wmake

Similarly, the generated executable is placed in the $FOAM_USER_APPBIN directory (as specified in Make/files).

4.4. Running

Run the following command in the terminal:

ofsp_03_wmake

The output is as follows:

Hi, OpenFOAM! Here we are.
1 + 3.14159 = 4.14159
1 * 3.14159 = 3.14159

Current time step is : 0.2

5. Summary

This section has completed the following discussions:

• A brief understanding of wmake
• Direct linking using wmake
• Dynamic library linking using wmake
• Understanding Make
• Compiling and running a wmake-based project

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• Code derived from OpenFOAM：GPL v3
• Other code：MIT License