alganet

Polyglot Makefiles

Alexandre Gomes Gaigalas – December 17, 2025

While Unix-like systems typically use GNU make, Windows environments based on Microsoft toolchains, traditionally use nmake. Although alternatives like GNU make on Windows exist (MSYS2, MinGW, WSL), many projects still need to support native nmake workflows.

Unfortunately, GNU make and nmake are similar tools with different syntax and features. This often leads to duplicated makefiles or forcing contributors to install a non-native tool. Here we explore a technique to create a single Makefile that works for both.

Why this is useful

• One source of truth: Common variables, targets and documentation live in a single Makefile.
• Platform delegation: Tool or platform-specific rules live in small, focused include files.
• Controlled complexity: The polyglot logic is isolated to a tiny, well-documented block.

The key bit

The polyglot solution for the unified Makefile looks like this:

SHARED_VAR = some_value

shared_target:
	echo 123

# --- POLYGLOT MAGIC BEGINS
# \
!ifndef 0 # \
!include "nmake-specific.mk" # \
!else
include gnu-specific.mk
# \
!endif
# --- POLYGLOT MAGIC ENDS

This single block allows each tool to include its own implementation file while sharing the same variables and targets.

How it works

This snippet relies on subtle but well-defined differences between GNU make and nmake parsing rules.

What GNU make sees:

GNU make supports line continuation (\) inside comments. Because of this, the !-prefixed nmake directives become part of a multi-line comment and are ignored.

# --- POLYGLOT MAGIC BEGINS
# \
!ifndef 0 # \
!include "nmake-specific.mk" # \
!else
include gnu-specific.mk
# \
!endif
# --- POLYGLOT MAGIC ENDS

What nmake sees:

nmake does not support multi-line comments. It recognizes the !ifndef, !include, !else, and !endif directives and evaluates the first branch.

The condition !ifndef 0 is intentionally chosen: 0 is not a predefined macro in nmake, so the condition is always true. This reliably selects the nmake-specific branch without depending on environment variables.

# --- POLYGLOT MAGIC BEGINS
# \
!ifndef 0 # \
!include "nmake-specific.mk" # \
!else
include gnu-specific.mk
# \
!endif
# --- POLYGLOT MAGIC ENDS

Typical file layout

Makefile
gnu-specific.mk
nmake-specific.mk

Caveats and limitations

• This relies on GNU make’s handling of line continuation inside comments.
• The polyglot block should remain small and self-contained.
• Editors or formatters that alter trailing backslashes may silently break this construct.

Final thoughts

Polyglot Makefiles are a powerful technique when used sparingly. They allow a single shared build definition while preserving native workflows on each platform.

This technique was used in the PHL repository to simplify the build process. Both Unix and Windows builds share a lot of variables and targets, leveraging a single source of truth for the built objects, dependencies and more.

CC BY-NC-SA 4.0