diff --git a/wmake/src/wmkdep.l b/wmake/src/wmkdep.l
index 5b8cd07235..82d6ae4b18 100644
--- a/wmake/src/wmkdep.l
+++ b/wmake/src/wmkdep.l
@@ -30,12 +30,15 @@ Description
     output of cpp -M. However, the output contains no duplicates and
     is approx. 40% faster than cpp.
 
-    The algorithm uses flex to scan for includes and searches the files
-    found.  Each file is entered into a hash table so that files are scanned
-    only once.  This is why this program is faster than cpp.
+    The algorithm uses flex to scan the directories specified with '-Idir'
+    options for include files and searches the files found.  Each file is
+    entered into a hash table so that files are scanned only once.  The
+    resulting file paths are added to the dependencies file after replacing
+    strings specified with the '-R string replacement' options.
 
 Usage
-    wmkdep [ -Idir ... -Idir ] filename
+    wmkdep [ -R string replacement ... -R string replacement ] \
+        [ -Idir ... -Idir ] <source file> <dependencies file>
 
 \*---------------------------------------------------------------------------*/
 
diff --git a/wmake/src/wmkdep.l.tree b/wmake/src/wmkdep.l.tree
deleted file mode 100644
index edf43a9983..0000000000
--- a/wmake/src/wmkdep.l.tree
+++ /dev/null
@@ -1,531 +0,0 @@
-%{
-/*---------------------------------*- C -*-----------------------------------*\
- =========                   |
- \\      /   F ield          | OpenFOAM: The Open Source CFD Toolbox
-  \\    /    O peration      |
-   \\  /     A nd            | Copyright (C) 2011-2018 OpenFOAM Foundation
-    \\/      M anipulation   |
-------------------------------------------------------------------------------
-License
-    This file is part of OpenFOAM.
-
-    OpenFOAM is free software: you can redistribute it and/or modify it
-    under the terms of the GNU General Public License as published by
-    the Free Software Foundation, either version 3 of the License, or
-    (at your option) any later version.
-
-    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
-    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
-    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
-    for more details.
-
-    You should have received a copy of the GNU General Public License
-    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
-
-Application
-    wmkdep
-
-Description
-    A fast dependency list generator that emulates the behaviour and the
-    output of cpp -M. However, the output contains no duplicates and
-    is approx. 40% faster than cpp.
-
-    The algorithm uses flex to scan for includes and searches the files
-    found.  Each file is entered into a hash table so that files are scanned
-    only once.  This is why this program is faster than cpp.
-
-Usage
-    wmkdep [ -Idir ... -Idir ] filename
-
-\*---------------------------------------------------------------------------*/
-
-#define FILE_STACK_SIZE 300
-#define HASH_TABLE_SIZE 500
-#define REPLACEMENTS_SIZE 10
-#define INITIAL_MAX_N_FILES 1000
-
-#include <stdlib.h>
-#include <string.h>
-#include <sys/types.h>
-#include <dirent.h>
-#include <errno.h>
-
-void nextFile(const char* fileName);
-void importFile(const char* fileName);
-void importDir(const char* dirName);
-void printFile(const char* pathName);
-void processFile(char* pathName);
-
-#undef yywrap        /* Sometimes a macro by default */
-
-%}
-
-%x CMNT CFNAME
-%%
-
-"//".*\n                  ;               /* Remove c++ style line comments */
-
-"/*"                      BEGIN(CMNT);    /* Start removing c style comment */
-<CMNT>.|\n                ;
-<CMNT>"*/"                BEGIN(INITIAL); /* End removing c style comment */
-
-^[ \t]*#[ \t]*include[ \t]+\"   BEGIN(CFNAME);  /* c-file name */
-<CFNAME>[^"\n ]*        { BEGIN(INITIAL); nextFile(yytext); } /*"*/
-
-.|\t|\n                   ;
-
-%%
-
-
-/* char* entry in hash table */
-struct HashEntry
-{
-    char* name;
-    struct HashEntry* next;
-};
-
-
-/* Lookup name in hash table.
-   If found - return 1
-   If not found - insert in table and return 0
-*/
-int lookUp(struct HashEntry** hashTable, const char* p)
-{
-    int ii = 0;
-    struct HashEntry* n;
-    struct HashEntry* nn;
-
-    /* Hash */
-    const char* pp = p;
-    while (*pp) ii = ii<<1 ^ *pp++;
-    if (ii < 0) ii = -ii;
-    ii %= HASH_TABLE_SIZE;
-
-    /* Search */
-    for (n=hashTable[ii]; n; n=n->next)
-    {
-        if (strcmp(p, n->name) == 0)
-        {
-            /* Entry found so return true */
-            return 1;
-        }
-    }
-
-    /* Insert */
-    nn = (struct HashEntry*)malloc(sizeof(struct HashEntry));
-    nn->name = strdup(p);
-    nn->next = hashTable[ii];
-    hashTable[ii] = nn;
-
-    /* Entry not found, and therefore added. return false */
-    return 0;
-}
-
-
-/* String search/replace pair */
-struct searchReplace
-{
-    char* search;
-    size_t searchLen;
-    char* replace;
-    size_t replaceLen;
-};
-
-
-/* String search/replace */
-char* strRep(char* str, struct searchReplace* sr)
-{
-    char* searchStart = strstr(str, sr->search);
-
-    if (searchStart  != NULL)
-    {
-        if (sr->replaceLen > sr->searchLen)
-        {
-            const size_t start = str - searchStart;
-            str = realloc
-            (
-                str,
-                strlen(str) + sr->replaceLen - sr->searchLen + 1
-            );
-            searchStart = str + start;
-        }
-
-        const size_t tailLen = strlen(searchStart + sr->searchLen);
-
-        memmove
-        (
-            searchStart + sr->replaceLen,
-            searchStart + sr->searchLen,
-            tailLen + 1
-        );
-
-        memcpy(searchStart, sr->replace, sr->replaceLen);
-    }
-
-    return str;
-}
-
-
-/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
-
-int nDirectories = 0;
-char** directories;
-char* sourceFile = NULL;
-char* depFile = NULL;
-
-int nReplacements = 0;
-struct searchReplace replacements[REPLACEMENTS_SIZE];
-
-/* Set of files already visited */
-struct HashEntry* visitedFiles[HASH_TABLE_SIZE];
-
-/* Buffer pointer stack counter */
-int currentBuffer = 0;
-
-/* Buffer pointer stack */
-YY_BUFFER_STATE buffers[FILE_STACK_SIZE];
-
-/* Directory paths for the loaded files */
-const char* bufferPaths[FILE_STACK_SIZE];
-
-/* List of dependency files */
-int nFiles = 0;
-int maxNfiles = INITIAL_MAX_N_FILES;
-char** files;
-
-
-int main(int argc, char* argv[])
-{
-    char *basePos, *dotPos;
-    int i;
-
-    if (argc == 1)
-    {
-        fprintf(stderr, "input file not supplied\n");
-        exit(1);
-    }
-
-    sourceFile = strdup(argv[argc-1]);
-
-    if ((basePos = strrchr(sourceFile, '/')) == NULL)
-    {
-        basePos = sourceFile;
-    }
-    else
-    {
-        basePos++;
-    }
-
-    if
-    (
-        (dotPos = strrchr(sourceFile, '.')) == NULL
-     || (dotPos < basePos)
-    )
-    {
-        fprintf
-        (
-            stderr,
-            "cannot find extension in source file name %s\n",
-            sourceFile
-        );
-        exit(1);
-    }
-
-    /* Build list of string replacements */
-    nReplacements = 0;
-    for (i = 1; i < argc; i++)
-    {
-        if (strncmp(argv[i], "-R", 2) == 0)
-        {
-            replacements[nReplacements].search = strdup(argv[++i]);
-            replacements[nReplacements].searchLen =
-                strlen(replacements[nReplacements].search);
-
-            replacements[nReplacements].replace = strdup(argv[++i]);
-            replacements[nReplacements].replaceLen =
-                strlen(replacements[nReplacements].replace);
-
-            nReplacements++;
-        }
-    }
-
-    /* Count number of -I directories */
-    nDirectories = 0;
-    for (i = 1; i < argc; i++)
-    {
-        if (strncmp(argv[i], "-I", 2) == 0)
-        {
-            if (strlen(argv[i]) > 2)
-            {
-                nDirectories++;
-            }
-        }
-    }
-
-    directories = (char**)malloc(sizeof(char*)*nDirectories);
-
-    /* Build list of -I directories */
-    nDirectories = 0;
-    for (i = 1; i < argc; i++)
-    {
-        if (strncmp(argv[i], "-I", 2) == 0)
-        {
-            if (strlen(argv[i]) > 2)
-            {
-                directories[nDirectories++] = strdup(argv[i] + 2);
-            }
-        }
-    }
-
-    /* Initialise depFile to zero and use strncat rather than strncpy
-       because there is a bug in the SGI strncat that if 0 precedes the '.'
-       it inserts a space
-    */
-    depFile = (char*)malloc(strlen(sourceFile) + 20);
-    depFile[0] = 0;
-    strcat(depFile, "$(OBJECTS_DIR)/");
-    strcat(depFile, sourceFile);
-    strcat(depFile, ".dep");
-
-    /* Initialise storage for the list of the dependencies */
-    files = (char**)malloc(sizeof(char*)*maxNfiles);
-
-    char *objectFile = strdup(basePos);
-    objectFile[(dotPos - basePos)/sizeof(char)] = 0;
-
-    /* printf("$(OBJECTS_DIR)/%s.o: %s\n", objectFile, depFile); */
-    printf("%s: \\\n", depFile);
-    free(objectFile);
-
-    /* Initialize buffer path for currentBuffer */
-    bufferPaths[currentBuffer] = NULL;
-
-    nextFile(sourceFile);
-    yylex();
-
-    puts("\n");
-
-    /* Write the dummy rules for the dependencies */
-    for (i = 0; i < nFiles; i++)
-    {
-        printf("%s :\n", files[i]);
-    }
-
-    puts("\n");
-
-    /*  Clean-up storage */
-
-    for (i = 0; i < nDirectories; i++)
-    {
-        free(directories[i]);
-    }
-    free(directories);
-
-    free(sourceFile);
-    free(depFile);
-
-    for (i = 0; i < nFiles; i++)
-    {
-        free(files[i]);
-    }
-    free(files);
-
-    return 0;
-}
-
-
-/* Add a directory name to the file name */
-char* addDirectoryName(const char* dirName, const char* fileName)
-{
-    char* pathName = (char*)malloc(strlen(dirName) + strlen(fileName) + 2);
-    strcpy(pathName, dirName);
-
-    if (dirName[strlen(dirName)-1] != '/')
-    {
-        strcat(pathName, "/");
-    }
-
-    strcat(pathName, fileName);
-
-    return pathName;
-}
-
-
-/* Open a file and create buffer and put on stack */
-void nextFile(const char* fileName)
-{
-    if (lookUp(visitedFiles, fileName))
-    {
-        return;   /* Already existed (did not insert) */
-    }
-
-    if (currentBuffer >= FILE_STACK_SIZE)
-    {
-        fprintf
-        (
-            stderr,
-            "depth of file search exceeds stack size %d "
-            "while opening %s for file %s\n",
-            FILE_STACK_SIZE, fileName, sourceFile
-        );
-        exit(1);
-    }
-
-    /* Pointer to new file which is set if the file is successfully opened */
-    FILE* newyyin = NULL;
-
-    /* Check if the file has same path as the file in the current buffer */
-    if (bufferPaths[currentBuffer] != NULL)
-    {
-        char* pathName = addDirectoryName(bufferPaths[currentBuffer], fileName);
-
-        if ((newyyin = fopen(pathName, "r")))
-        {
-            processFile(pathName);
-
-            buffers[currentBuffer++] = YY_CURRENT_BUFFER;
-            bufferPaths[currentBuffer] = bufferPaths[currentBuffer-1];
-
-            yy_switch_to_buffer(yy_create_buffer(newyyin, YY_BUF_SIZE));
-
-            return;
-        }
-
-        free(pathName);
-    }
-
-    if (!(newyyin = fopen(fileName, "r")))
-    {
-        int d;
-        for (d=0; d<nDirectories; d++)
-        {
-            char* pathName = addDirectoryName(directories[d], fileName);
-
-            if ((newyyin = fopen(pathName, "r")))
-            {
-                processFile(pathName);
-
-                buffers[currentBuffer++] = YY_CURRENT_BUFFER;
-                bufferPaths[currentBuffer] = directories[d];
-
-                yy_switch_to_buffer(yy_create_buffer(newyyin, YY_BUF_SIZE));
-
-                return;
-            }
-
-            free(pathName);
-        }
-
-        if (nDirectories == 0)
-        {
-            fprintf
-            (
-                stderr,
-                "could not open file %s for source file %s\n",
-                fileName, sourceFile
-            );
-        }
-        else
-        {
-            fprintf
-            (
-                stderr,
-                "could not open file %s for source file %s due to %s\n",
-                fileName, sourceFile, strerror(errno)
-            );
-        }
-
-        fflush(stdout);
-        fflush(stderr);
-
-        /* Only report the first occurrence */
-        lookUp(visitedFiles, fileName);
-    }
-    else
-    {
-        printFile(fileName);
-        fflush(stdout);
-
-        buffers[currentBuffer++] = YY_CURRENT_BUFFER;
-        bufferPaths[currentBuffer] = NULL;
-
-        yy_switch_to_buffer(yy_create_buffer(newyyin, YY_BUF_SIZE));
-    }
-}
-
-
-void printFile(const char* pathName)
-{
-    printf("%s \\\n", pathName);
-}
-
-
-/* Replace path strings and print resulting path */
-void processFile(char* pathName)
-{
-    if (nFiles == maxNfiles - 1)
-    {
-        maxNfiles *= 2;
-        files = (char**)realloc(files, sizeof(char*)*maxNfiles);
-    }
-
-    if (nReplacements)
-    {
-        int i;
-        for (i=0; i<nReplacements; i++)
-        {
-            pathName = strRep(pathName, &replacements[i]);
-        }
-    }
-
-    printFile(pathName);
-    files[nFiles++] = pathName;
-}
-
-
-/* Replace all '.' with '/' */
-void dotToSlash(char* fileName)
-{
-    const int len = strlen(fileName);
-
-    int i;
-    for (i=0; i<len; i++)
-    {
-        if (fileName[i] == '.') fileName[i] = '/';
-    }
-}
-
-
-/* The lexer calls yywrap to handle EOF conditions */
-int yywrap()
-{
-    /* Delete the buffer */
-    yy_delete_buffer(YY_CURRENT_BUFFER);
-
-    /* Set buffer counter to previous buffer */
-    currentBuffer--;
-
-    /* Close the file for the buffer which has just reached EOF */
-    fclose(yyin);
-    yyin = 0;
-
-    if (currentBuffer > 0) /* If buffer counter refers to a valid file */
-    {
-        /* Reset input buffer to the previous buffer on the stack */
-        yy_switch_to_buffer(buffers[currentBuffer]);
-
-        /* Return to the normal state for the previous buffer on the stack */
-        BEGIN(INITIAL);
-
-        /* Return 0 to inform lex to continue reading */
-        return 0;
-    }
-    else                 /* Else there are no more buffers on the stack */
-    {
-        /* Return 1 to inform lex finish now that all buffers have been read */
-        return 1;
-    }
-}
-
-
-/*****************************************************************************/