Home > Articles > Programming > C/C++

This chapter is from the book

Using qmake

The qmake tool is supplied with Qt. It is used to build Qt itself as well as the tools and examples that accompany it. Throughout the book, we have used qmake project (.pro) files to build our example applications and plugins. In this section, we will study the .pro file syntax in a more systematic (although by no means comprehensive) way, and we will review a few fundamental qmake concepts. For complete coverage, see the qmake manual, available online at http://doc.trolltech.com/4.3/qmake-manual.html.

The purpose of a .pro file is to list the source files that are involved in a project. Since qmake is used for building Qt and its associated tools, it knows Qt very well and can generate rules for invoking moc, uic, and rcc. As a result, the syntax is very concise and easy to learn.

The three main types of project files are app (for stand-alone applications), lib (for static and shared libraries), and subdirs (for recursive subdirectory builds). This can be specified using the TEMPLATE variable, as follows:


The subdirs template can be used for building targets in subdirectories. In that case, we need to specify only the SUBDIRS variable in addition to TEMPLATE = subdirs. In each subdirectory, qmake looks for a .pro file named after the directory and will build that project. The examples.pro file supplied with the examples provided for this book uses the subdirs template to run qmake on the individual examples.

If no TEMPLATE entry is present, the default is app. For app or lib projects, the most commonly used variables are the following:

  • HEADERS specifies the project's C++ header (.h) files.
  • SOURCES specifies the project's C++ implementation (.cpp) files.
  • FORMS specifies the Qt Designer .ui files to be processed by uic.
  • RESOURCES specifies the .qrc files to be processed by rcc.
  • DEFINES specifies the C++ preprocessor symbols that should be predefined.
  • INCLUDEPATH specifies the directories that should be searched by the C++ preprocessor for locating global header files.
  • LIBS specifies the libraries to link to the project. The libraries are specified either as absolute paths or using the Unix-inspired -L and -l flags (e.g., -L/usr/local/lib and -ldb_cxx).
  • CONFIG specifies various project configuration and compiler options.
  • QT specifies the Qt modules that are used by the project. (The default is core gui, corresponding to the QtCore and QtGui modules.)
  • VERSION specifies the version number of the target library.
  • TARGET specifies the base name of the target executable or library, excluding any extension, prefix, or version number. (The default is the name of the current directory.)
  • DESTDIR specifies the directory in which the target executable should be put. (The default is platform-dependent; for example, on Linux, it is the current directory, and on Windows, it is the debug or release subdirectory.)
  • DLLDESTDIR specifies the directory in which the target library file should be put. (It has the same default as DESTDIR.)

The CONFIG variable is used to control various aspects of the build process. The following options are supported:

  • debug means that an executable or library with debugging information should be built, and links against the debug versions of the Qt libraries.
  • release means that an executable or library without debugging information should be built, and links against the release versions of the Qt libraries. If both debug and release are specified, debug wins.
  • warn_off switches off as many warnings as possible. By default, builds are done with warnings switched on.
  • qt means that the application or library uses Qt. This option is included by default.
  • dll means that a shared library should be built.
  • staticlib means that a static library should be built.
  • plugin means that a plugin should be built. Plugins are always shared libraries, so this option implies the dll option.
  • console means that the application needs to write to the console (using cout, cerr, qWarning(), etc.).
  • app_bundle applies only to Mac OS X builds, and means that the executable should be put in a bundle, which is the default on Mac OS X.
  • lib_bundle applies only to Mac OS X builds, and means that the library should be put in a framework.

To generate a makefile for a project file called hello.pro, we type

qmake hello.pro

After that, we can invoke make or nmake to build the project. We can also use qmake to generate a Microsoft Visual Studio project (.dsp or .vproj) file by typing

qmake -tp vc hello.pro

On Mac OS X, we can generate an Xcode project file using

qmake -spec macx-xcode hello.pro

and makefiles using

qmake -spec macx-g++ hello.pro

The -spec command-line option lets us specify a platform/compiler combination. Normally, qmake detects the correct platform, but in some cases it may be necessary to specify it explicitly. For example, to generate a makefile that invokes the Intel C++ Compiler (ICC) for Linux in 64-bit mode, we would type

qmake -spec linux-icc-64 hello.pro

The possible specifications are located in Qt's mkspecs directory.

Although qmake's primary purpose is to generate makefiles from .pro files, we can also use qmake to generate a .pro file for the current directory, using the -project option. For example:

qmake -project

In this mode, qmake will search the current directory for files with known extensions (.h, .cpp, .ui, etc.) and produce a .pro file that lists these files.

In the rest of this section, we will look in more detail at the .pro file syntax. A .pro file entry normally has the syntax

variable = values

where values is a list of string values. Comments start with the pound sign (#) and terminate at the end of the line. For example, the line

CONFIG = qt release warn_off       # I know what I'm doing

assigns the list ["qt", "release", "warn_off"] to the CONFIG variable, overwriting any previous values. Additional operators are provided to supplement the = operator. The += operator lets us append values to a variable. Thus, the lines

CONFIG  = qt
CONFIG += release
CONFIG += warn_off

effectively assign the list ["qt", "release", "warn_off"] to CONFIG, just as the previous example did. The -= operator removes all occurrences of the specified values from the variable's current value. Thus,

CONFIG  = qt release warn_off
CONFIG -= qt

leaves CONFIG with the list ["release", "warn_off"]. The *= operator adds a value to a variable, but only if the value is not already in the variable's list; otherwise, it does nothing. For example, the line

SOURCES *= main.cpp

will add the implementation file main.cpp to the project only if it isn't specified already. Finally, the ~= operator can be used to replace any values that match a regular expression with the specified replacement text, using a syntax inspired by sed (the Unix stream editor). For example,

SOURCES ~= s/\.cpp\b/.cxx/

replaces all .cpp file extensions with .cxx in the SOURCES variable.

Inside the list of values, qmake provides ways to access the values of other qmake variables, of environment variables, and of Qt configuration options. The syntaxes are listed in Figure B.2.

Table B.2. Variable accessors available in qmake



$$ varName or $${ varName }

Value of qmake variable at that point in the .pro file

$$( varName )

Value of environment variable when qmake is run

$( varName )

Value of environment variable when makefile is processed

$$[ varName ]

Value of Qt configuration option

In the examples so far, we always used standard variables, such as SOURCES and CONFIG, but it is possible to set the value of any variable and to refer to it later using the $$ varName or $${ varName } syntax. For example:

MY_VERSION    = 1.2
SOURCES_BASIC = alphadialog.cpp                 main.cpp                 windowpanel.cpp
SOURCES_EXTRA = bezierextension.cpp                 xplot.cpp
SOURCES       = $$SOURCES_BASIC                 $$SOURCES_EXTRA
TARGET        = imgpro_$${MY_VERSION}

The next example combines several of the syntaxes shown earlier and uses the built-in function $$lower() to convert strings to lowercase:

# List of classes in the project
MY_CLASSES    = Annotation                 CityBlock                 CityScape                 CityView

# Append .cpp extension to lowercased class names, and add main.cpp
SOURCES       = $$lower($$MY_CLASSES)
SOURCES      ~= s/([a-z0-9_]+)/\1.cpp/
SOURCES      += main.cpp
# Append .h extension to lowercased class names
HEADERS       = $$lower($$MY_CLASSES)
HEADERS      ~= s/([a-z0-9_]+)/\1.h/

Sometimes we may need to specify file names that include spaces in a .pro file. In that case, we can simply put quotes around the file name.

When compiling a project on different platforms, it might be necessary to specify different files or different options based on the platform. The general syntax for conditionals in qmake is

condition {
} else {

The condition part can be a platform name (e.g., win32, unix, or macx) or a more complex predicate. The then-case and else-case parts specify the values of variables using the standard syntax. For example:

win32 {
    SOURCES += serial_win.cpp
} else {
    SOURCES += serial_unix.cpp

The else branch is optional. For convenience, qmake also supports a one-line syntax when the then-case part consists of only one variable assignment and there is no else-case :


For example:

macx:SOURCES += serial_mac.cpp

If we have several project files that need to share some of the same entries, we can factor out the common entries in a separate file and include it in the individual .pro files that need it using the include() directive:


HEADERS      += window.h
SOURCES      += main.cpp                 window.cpp

Conventionally, project files that are meant to be included by other project files are given a .pri (project include) extension.

In a previous example, we saw the $$lower() built-in function, which returns a lowercase version of its argument. Another useful function is $$system(): It allows us to generate strings from external applications. For example, if we need to determine which version of Unix is being used, we can write

OS_VERSION = $$system(uname -r).

We can then use the resulting variable in a condition, together with contains():

contains(OS_VERSION, SunOS):SOURCES += mythread_sun.c

In this section, we have barely skimmed the surface. The qmake tool provides many more options and features than we presented here, including support for precompiled headers, for Mac OS X universal binaries, and for user-defined compilers or tools. Refer to the online qmake manual for full details.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020