Report a bug
If you spot a problem with this page, click here to create a Bugzilla issue.
Improve this page
Quickly fork, edit online, and submit a pull request for this page. Requires a signed-in GitHub account. This works well for small changes. If you'd like to make larger changes you may want to consider using a local clone.

DMD Compiler for Windows

Requirements and Downloads

  1. DMD Compiler
  2. Windows operating system, Windows 7 or later, 32 or 64 bit
  3. Download (C and C++ compiler) for Win32 (not required, but it complements dmd for Windows)


Hint - The official installer performs these steps automatically.

Open a console window (for Windows this is done by clicking on [Start][Command Prompt]). All the tools are command line tools, which means they are run from a console window. Switch to the root directory. Unzip the files in the root directory. will create a \dmd2 directory with all the files in it. will create a \dm directory with all the files in it.

A typical session might look like:

C:\Documents and Settings\Your Name>cd \




in the \dmd2\samples\d directory for several small examples.

Compiler Arguments and Switches

dmd files... -switches...
File Extensions
Extension File Type
none D source files
.c C source files
.d D source files
.dd Ddoc source files
.di D interface files
.i preprocessed C source files
.obj Object files to link in
.lib Object code libraries to search
.exe Output executable file
.def module definition file
.res resource file
If cmdfile is an environment variable, read the compiler arguments and switches from the value of that variable. Otherwise, read compiler arguments and switches from the text file cmdfile. The file may contain single-line comments starting with the hash symbol (#).
Generate code for all template instantiations
Adjusts the compiler to implement D as a better C:
  • Predefines D_BetterC version.
  • Assert Expressions, when they fail, call the C runtime library assert failure function rather than a function in the D runtime.
  • Array overflows call the C runtime library assert failure function rather than a function in the D runtime.
  • Final switch errors call the C runtime library assert failure function rather than a function in the D runtime.
  • Does not automatically link with phobos runtime library.
  • Module constructors and destructors are not generated meaning that static and shared static constructors and destructors will not get called.
  • ModuleInfo is not generated.
  • TypeInfo instances will not be generated for structs.
-boundscheck=[on|safeonly|off ]
Controls if bounds checking is enabled.
  • on: Bounds checks are enabled for all code. This is the default.
  • safeonly: Bounds checks are enabled only in @safe code. This is the default for -release builds.
  • off: Bounds checks are disabled completely (even in @safe code). This option should be used with caution and as a last resort to improve performance. Confirm turning off @safe bounds checks is worthwhile by benchmarking.
Compile only, do not link
-check=[assert|bounds|in|invariant|out|switch ][=[on|off]]
Overrides default, -boundscheck, -release and -unittest options to enable or disable specific checks.
  • assert: assertion checking
  • bounds: array bounds
  • in: in contracts
  • invariant: class/struct invariants
  • out: out contracts
  • switch: final switch failure checking
  • on or not specified: specified check is enabled.
  • off: specified check is disabled.
-check=[h|help|? ]
List information on all available checks
-checkaction=[D|C|halt|context ]
Sets behavior when an assert or an array bounds check fails, or a final switch errors.
  • D: Default behavior, which throws an unrecoverable AssertError.
  • C: Calls the C runtime library assert failure function.
  • halt: Executes a halt instruction, terminating the program.
  • context: Prints the error context as part of the unrecoverable AssertError.
-checkaction=[h|help|? ]
List information on all available check actions
Turn colored console output on
-color=[on|off|auto ]
Show colored console output. The default depends on terminal capabilities.
  • auto: use colored output if a tty is detected (default)
  • on: always use colored output.
  • off: never use colored output.
Use config file at filename
Do code coverage analysis
Include code executed during CTFE in coverage report
Perform code coverage analysis and generate .lst file with report.
dmd -cov -unittest myprog.d
Normally the C preprocessor used by the associated C compiler is used to preprocess ImportC files, this is overridden by the -cpp switch.

Generate documentation from source.

Note: mind the security considerations.

Write documentation file to directory . -op can be used if the original package hierarchy should be retained
Write documentation file to filename
Silently allow deprecated features and use of symbols with deprecated attributes.
Issue an error when deprecated features or symbols are used (halt compilation)
Issue a message when deprecated features or symbols are used (default)
Compile in debug code
Compile in debug level <= level
Compile in debug identifier ident
Link in libname as the default library when compiling for symbolic debugging instead of phobos.lib. If libname is not supplied, then no default library is linked in.
Link in libname as the default library when not compiling for symbolic debugging instead of phobos.lib. If libname is not supplied, then no default library is linked in.
Print module dependencies (imports/file/version/debug/lib)
Without filename, print module dependencies (imports/file/version/debug/lib). With filename, write module dependencies as text to filename (only imports).
Which global variables to dllimport implicitly if not defined in a root module
  • none: None
  • defaultLibsOnly: Only druntime/Phobos symbols
  • all: All
Standards supported are:
  • c++98: Use C++98 name mangling, Sets __traits(getTargetInfo, "cppStd") to 199711
  • c++11 (default): Use C++11 name mangling, Sets __traits(getTargetInfo, "cppStd") to 201103
  • c++14: Use C++14 name mangling, Sets __traits(getTargetInfo, "cppStd") to 201402
  • c++17: Use C++17 name mangling, Sets __traits(getTargetInfo, "cppStd") to 201703
  • c++20: Use C++20 name mangling, Sets __traits(getTargetInfo, "cppStd") to 202002
-extern-std=[h|help|? ]
List all supported standards
Generate Indirect Branch Tracking code
Generate position independent code
Generate position independent executables
Add CodeView symbolic debug info. See Debugging on Windows.
The value of version may be 3, 4 or 5, defaulting to 3.
Symbolic debug info is emitted for all types referenced by the compiled code, even if the definition is in an imported file not currently being compiled.
Always emit stack frame
Adds stack stomp code, which overwrites the stack frame memory upon function exit.
Generate D interface file
Write D interface file to directory. -op can be used if the original package hierarchy should be retained.
Write 'header' file to filename
-HC[=[?|h|help|silent|verbose ]]
Write C++ 'header' equivalent to stdout configured with:",
list available options for C++ 'header' file generation
only list extern(C[++]) declarations (default)
also add comments for ignored declarations (e.g. extern(D))
Write C++ 'header' file to directory, ignored if -HCf= is not present
Write C++ 'header' file to filename instead of stdout
Print help and exit
Look for imports also in directory
-i[=pattern ]

Enables "include imports" mode, where the compiler will include imported modules in the compilation, as if they were given on the command line. By default, when this option is enabled, all imported modules are included except those in druntime/phobos. This behavior can be overridden by providing patterns via -i=<pattern>. A pattern of the form -i=<package> is an "inclusive pattern", whereas a pattern of the form -i=-<package> is an "exclusive pattern". Inclusive patterns will include all module's whose names match the pattern, whereas exclusive patterns will exclude them. For example. all modules in the package can be included using or excluded using Note that each component of the fully qualified name must match the pattern completely, so the pattern would not match a module named foo.barx.

The default behavior of excluding druntime/phobos is accomplished by internally adding a set of standard exclusions, namely, -i=-std -i=-core -i=-etc -i=-object. Note that these can be overridden with -i=std -i=core -i=etc -i=object.

When a module matches multiple patterns, matches are prioritized by their component length, where a match with more components takes priority (i.e. pattern has priority over

By default modules that don't match any pattern will be included. However, if at least one inclusive pattern is given, then modules not matching any pattern will be excluded. This behavior can be overridden by usig -i=. to include by default or -i=-. to exclude by default.

Note that multiple -i=... options are allowed, each one adds a pattern.

Set the identifier table to use for the non-ASCII values.
  • UAX31: UAX31
  • c99: C99
  • c11: C11
  • all: All, the least restrictive set, which comes with all others (default)
Set the identifier table to use for the non-ASCII values.
  • UAX31: UAX31
  • c99: C99
  • c11: C11 (default)
  • all: All, the least restrictive set, which comes with all others
Deprecated flag, unsupported pragmas are always ignored now
Inline functions at the discretion of the compiler. This can improve performance, at the expense of making it more difficult to use a debugger on it.
Where to look for files for ImportExpressions. This switch is required in order to use ImportExpressions. path is a ; separated list of paths. Multiple -J's can be used, and the paths are searched in the same order.
Pass linkerflag to the linker optlink.exe , for example, ld
Generate library file as output instead of object file(s). All compiled source files, as well as object files and library files specified on the command line, are inserted into the output library. Compiled source modules may be partitioned into several object modules to improve granularity. The name of the library is taken from the name of the first source module to be compiled. This name can be overridden with the -of switch.
Enable the garbage collector for the compiler, reducing the compiler memory requirements but increasing compile times.
Generate 32 bit code and write MS-COFF object files (deprecated use -m32)
The generated object code is in MS-COFF and is meant to be used with the Microsoft Visual Studio 10 or later compiler.
Add a default main() function when compiling. This is useful when unittesting a library, as it enables running the unittests in a library without having to manually define an entry-point function.
-makedeps[=filename ]
Print dependencies in Makefile compatible format. If filename is omitted, it prints to stdout. The emitted targets are the compiled artifacts (executable, object files, libraries). The emitted dependencies are imported modules and imported string files (via -J switch). Special characters in a dependency or target filename are escaped in the GNU Make manner.
Open default browser on this page
Generate a .map file
Set the target architecture for code generation, where:
list alternatives
the minimum architecture for the target platform (default)
generate AVX instructions instead of SSE instructions for vector and floating point operations. Not available for 32 bit memory models other than OSX32.
use the architecture the compiler is running on
-mcpu=[h|help|? ]
List all architecture options
Expand and save mixins to file specified by filename
If building MS-COFF object files when targeting Windows, embed a reference to the given C runtime library libname into the object file containing main, DllMain or WinMain for automatic linking. The default is libcmt (release version with static linkage), the other usual alternatives are libcmtd, msvcrt and msvcrtd. If no Visual C installation is detected, a wrapper for the redistributable VC2010 dynamic runtime library and mingw based platform import libraries will be linked instead using the LLD linker provided by the LLVM project. The detection can be skipped explicitly if msvcrt120 is specified as libname. If libname is empty, no C runtime library is automatically linked in.
-mv=package.module =
Use path/filename as the source file for package.module. This is used when the source file path and names are not the same as the package and module hierarchy. The rightmost components of the path/filename and package.module can be omitted if they are the same.
Turns off all array bounds checking, even for safe functions. Deprecated (use -boundscheck=off instead).
Turns off generation of exception stack unwinding code, enables more efficient code for RAII objects.
Optimize generated code. For fastest executables, compile with the -O -release -inline -boundscheck=off switches together.
Suppress generation of object file. Useful in conjuction with -D or -H flags.
Write object files relative to directory objdir instead of to the current directory. -op can be used if the original package hierarchy should be retained
Set output file name to filename in the output directory. The output file can be an object file, executable file, or library file depending on the other switches.
Normally the path for .d source files is stripped off when generating an object, interface, or Ddoc file name. -op will leave it on.
Set the target operating system as other than the host.
  • host: Target the host operating system (default).
  • dragonflybsd: DragonFlyBSD
  • freebsd: FreeBSD
  • linux: Linux
  • openbsd: OpenBSD
  • osx: OSX
  • solaris: Solaris
  • windows: Windows
Pass preprocessorflag to cl.exe
Preview an upcoming language change identified by id
-preview=[h|help|? ]
List all upcoming language changes
Instrument the generated code so that runtime performance data is collected when the generated program is run. Upon completion of the generated program, the files trace.log and trace.def are generated. trace.log has two sections,
  1. Fan in and fan out for each profiled function. The name of the function is left-justified, the functions immediately preceding it are the other functions that call it (fan in) and how many times it is called. The functions immediately following are the functions that are called (fan out) and how many times it calls that function. The function itself has 3 numbers appended: the aggregate of the fan in counts, the tree time used by the function which is the function time plus the tree times of all the functions it calls, and the time used excluding the time used by fan out.
  2. Timing data for each function, sorted from most used to least.
The trace.def file contains linker commands to associate functions which are strongly coupled so they appear adjacent in the resulting executable file. For more information see profile
  • gc: Instrument calls to GC memory allocation and write a report to the file profilegc.log upon program termination. Note: Only instrumented calls will be logged. These include:
    • Language constructs that allocate memory
    • Phobos functions that allocate GC memory
    • GC allocations via core.memory.GC
    Allocations made by other means will not be logged, including direct calls to the GC's C API.
Compile release version, which means not emitting run-time checks for contracts and asserts. Array bounds checking is not done for system and trusted functions, and assertion failures are undefined behaviour.
Revert language change identified by id
-revert=[h|help|? ]
List all revertable language changes
-run srcfile
Compile, link, and run the program srcfile with the rest of the command line, args..., as the arguments to the program. No .obj or executable file is left behind.
Generate DLL library
arch is the architecture: either x86, x64, x86_64 or x32, vendor is always ignored, but supported for easier interoperability, os is the operating system, this may have a trailing version number: freestanding for no operating system, darwin or osx for MacOS, dragonfly or dragonflybsd for DragonflyBSD, freebsd, openbsd, linux, solaris or windows for their respective operating systems. cenv is the C runtime environment and is optional: musl for musl-libc, msvc for the MSVC runtime, bionic for the Andriod libc, gnu or glibc for the GCC C runtime, newlib or uclibc for their respective C runtimes. ($ I cppenv) is the C++ runtime environment: clang for the LLVM C++ runtime, gcc for GCC's C++ runtime, msvc for microsoft's MSVC C++ runtime, sun for Sun's C++ runtime.
Show additional info about language change identified by id
-transition=[h|help|? ]
List all language changes
Compile in unittest code, turns on asserts, and sets the unittest version identifier
Enable verbose output for each compiler pass
List generated assembler for each function
Print character (column) numbers in diagnostics
-verror-style=[digitalmars|gnu ]
Set the style for file/line number annotations on compiler messages, where:
'file(line[,column]): message'. This is the default.
'file:line[:column]: message', conforming to the GNU standard used by gcc and clang.
Limit the number of supplemental messages for each error (0 means unlimited)
Limit the number of error/deprecation messages (0 means unlimited)
Show error messages with the context of the erroring source line
Show errors from speculative compiles such as __traits(compiles,...)
Print compiler version and exit
Compile in version level >= level
Compile in version identifier ident
List all gc allocations including hidden ones
  • default: Hidden for Windows targets without -shared, otherwise public
  • hidden: Only export symbols marked with 'export'
  • public: Export all symbols
List all variables going into thread local storage
-vtemplates=[list-instances ]
An optional argument determines extra diagnostics, where:
Also shows all instantiation contexts for each template.
Enable warnings
Enable informational warnings (i.e. compilation still proceeds normally)
Enable warnings about use of obsolete features that may be problematic (compilation still proceeds normally)
Generate JSON file
Write JSON file to filename
Pass driverflag to the linker driver ($CC or cc)

Empty switches, i.e. "", are ignored.


D runtime library source
D compiler front end source under dual (GPL and Artistic) license
Sample D programs
D symbol demangler
D manual lookup tool
D compiler executable
D's package manager
D source code minimizer
\dmd2\windows\bin$(LINK2, make.exe)
Digitalmars Make
Find/replace text in files
D build tool for script-like D code execution
Global compiler settings
\dmd2\windows\bin$(LINK2, shell.exe)
Simple command line shell
D runtime library


Linking is done directly by the dmd compiler after a successful compile. To prevent dmd from running the linker, use the -c switch.

32 bit programs must be linked with the D runtime library phobos.lib, followed by the Digital Mars C runtime library snn.lib. This is done automatically as long as the directories for the libraries are on the LIB environment variable path. A typical way to set LIB would be:

set LIB=\dmd2\lib;\dm\lib

If the dmd command is used to both compile and link to an executable, it will make certain optimizations that are valid only for Windows executable files. Do not use the resulting .obj files in a DLL. To compile modules into .obj files that can be used in an exe or DLL, compile with -c and -shared.

Linking 32 bit programs is done using Digital Mars optlink.exe.

Linking 64 bit programs is done using the Microsoft linker by default. If the Microsoft linker is not found, the included LLVM linker LLD will be used.

Environment Variables

The D compiler dmd uses the following environment variables:

The value of DFLAGS is treated as if it were appended to the command line to dmd.exe.
The linker uses LIB to search for library files. For D, it will normally be set to:
set LIB=\dmd2\lib;\dm\lib
dmd normally runs the linker by looking for optlink.exe along the PATH. To use a specific linker for 32 bit programs instead, set the LINKCMD environment variable to it. For example:
set LINKCMD=\dmd\windows\bin\link
dmd normally runs the linker by looking for optlink.exe along the PATH. To use a specific linker for 64 bit programs instead, set the LINKCMD64 environment variable to it. For example:
set LINKCMD64=C:\Program Files (x86)\Microsoft Visual Studio 15.0\VC\bin\amd64\link.exe
If the linker is not found in the same directory as dmd.exe is in, the PATH is searched for it. Note: other linkers named link.exe will likely not work. Make sure the Digital Mars optlink.exe is found first in the PATH before other link.exes, or use LINKCMD to specifically identify which linker to use.

sc.ini Initialization File

dmd will look for the initialization file sc.ini in the following sequence of directories:

  1. current working directory
  2. directory specified by the HOME environment variable
  3. directory dmd.exe resides in

If found, environment variable settings in the file will override any existing settings. This is handy to make dmd independent of programs with conflicting use of environment variables.

Initialization File Format

Comments are lines that begin with ; and are ignored.

Environment variables follow the [Environment] section heading, in NAME=value pairs. The NAMEs are treated as upper case. Comments are lines that start with ;. For example:

; sc.ini file for dmd
; Names enclosed by %% are searched for in the existing environment
; and inserted. The special name %@P% is replaced with the path
; to this file.

DFLAGS="-I%@P%..\src\phobos" "-I%@P%..\src\druntime\import"

Location Independence of sc.ini

The %@P% is replaced with the path to sc.ini. Thus, if the fully qualified file name sc.ini is c:\dmd2\bin\sc.ini, then %@P% will be replaced with c:\dmd2\bin, and the above sc.ini will be interpreted as:


DFLAGS="-Ic:\dmd2\bin..\src\phobos" "-Ic:\dmd2\bin..\src\druntime\import"

This enables your dmd setup to be moved around without having to re-edit sc.ini.

Common Installation Problems

Differences between Windows and Linux versions

D Interface Files

When an import declaration is processed in a D source file, the compiler searches for the D source file corresponding to the import, and processes that source file to extract the information needed from it. Alternatively, the compiler can instead look for a corresponding D interface file. A D interface file contains only what an import of the module needs, rather than the whole implementation of that module.

The advantages of using a D interface file for imports rather than a D source file are:

D interface files can be created by the compiler from a D source file by using the -H switch to the compiler. D interface files have the .di file extension. When the compiler resolves an import declaration, it first looks for a .di D interface file, then it looks for a D source file.

D interface files bear some analogous similarities to C++ header files. But they are not required in the way that C++ header files are, and they are not part of the D language. They are a feature of the compiler, and serve only as an optimization of the build process.

Building Executables

dmd can build an executable much faster if as many of the source files as possible are put on the command line.

Another advantage to putting multiple source files on the same invocation of dmd is that dmd will be able to do some level of cross-module optimizations, such as function inlining across modules.

The -i flag can be used to automatically compile imported modules

Building Libraries

There are three ways to build a library. For example, given foo.d and bar.d which are to be compiled, and existing object file abc.obj and existing library def.lib which are all to be combined into a library foo.lib:

  1. Compile modules separately and then run the librarian on them:
    dmd -c foo.d
    dmd -c bar.d
    phobos.lib -c -p32 foo.lib foo.obj bar.obj abc.obj def.lib
    del foo.obj bar.obj
    This option is typical when using a makefile to avoid compiling modules that have already been compiled.
  2. Compile modules together and then run the librarian on them:
    dmd -c foo.d bar.d
    phobos.lib -c -p32 foo.lib foo.obj bar.obj abc.obj def.lib
    del foo.obj bar.obj
  3. Use dmd to compile and build library in one operation:
    dmd -lib foo.d bar.d abc.obj def.lib
    No object files are written to disk, it's all done in memory. Using -lib also has the advantage that modules may be compiled into multiple object files rather than exactly one per module. This improves granularity of the library without having to break up the modules.

Compiling dmd

Complete source code is provided to build the compiler. Follow these steps:

cd \dmd2\src\dmd
make -f win32.mak

Compiling Phobos

Complete source code is provided to build Phobos, the D runtime library. Follow these steps:

cd \dmd2\src\druntime
make -f win32.mak
cd ..\phobos
make -f win32.mak