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NAME | SYNOPSIS | DESCRIPTION | COMMANDS | SUPPORTED FLAGS | FEATURE AREAS | ENVIRONMENT | FILES | EXAMPLES | COLOPHON |
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dpkg-buildflags(1) dpkg suite dpkg-buildflags(1)
dpkg-buildflags - returns build flags to use during package build
dpkg-buildflags [option...] [command]
dpkg-buildflags is a tool to retrieve compilation flags to use
during build of Debian packages.
The default flags are defined by the vendor but they can be
extended/overridden in several ways:
1. system-wide with /usr/local/etc/dpkg/buildflags.conf;
2. for the current user with
$XDG_CONFIG_HOME/dpkg/buildflags.conf where $XDG_CONFIG_HOME
defaults to $HOME/.config;
3. temporarily by the user with environment variables (see
section "ENVIRONMENT");
4. dynamically by the package maintainer with environment
variables set via debian/rules (see section "ENVIRONMENT").
The configuration files can contain four types of directives:
SET flag value
Override the flag named flag to have the value value.
STRIP flag value
Strip from the flag named flag all the build flags listed in
value.
Supported since dpkg 1.16.1.
APPEND flag value
Extend the flag named flag by appending the options given in
value. A space is prepended to the appended value if the
flag's current value is non-empty.
PREPEND flag value
Extend the flag named flag by prepending the options given in
value. A space is appended to the prepended value if the
flag's current value is non-empty.
Supported since dpkg 1.16.1.
The configuration files can contain comments on lines starting
with a hash (#). Empty lines are also ignored.
This program was introduced in dpkg 1.15.7.
--dump
Print to standard output all compilation flags and their
values. It prints one flag per line separated from its value
by an equal sign (“flag=value”). This is the default action.
--list
Print the list of flags supported by the current vendor (one
per line). See the "SUPPORTED FLAGS" section for more
information about them.
--status
Display any information that can be useful to explain the
behavior of dpkg-buildflags: relevant environment variables,
current vendor, state of all feature flags. Also print the
resulting compiler flags with their origin.
This is intended to be run from debian/rules, so that the
build log keeps a clear trace of the build flags used. This
can be useful to diagnose problems related to them.
Supported since dpkg 1.16.5.
--export=format
Print to standard output commands that can be used to export
all the compilation flags for some particular tool. If the
format value is not given, sh is assumed. Only compilation
flags starting with an upper case character are included,
others are assumed to not be suitable for the environment.
Supported formats:
sh Shell commands to set and export all the compilation flags
in the environment. The flag values are quoted so the
output is ready for evaluation by a shell.
cmdline
Arguments to pass to a build program's command line to use
all the compilation flags. The flag values are quoted in
shell syntax.
Supported since dpkg 1.17.0.
configure
This is a legacy alias for cmdline.
make
Make directives to set and export all the compilation
flags in the environment. Output can be written to a
Makefile fragment and evaluated using an include
directive.
--get flag
Print the value of the flag on standard output. Exits with 0
if the flag is known otherwise exits with 1.
--origin flag
Print the origin of the value that is returned by --get.
Exits with 0 if the flag is known otherwise exits with 1. The
origin can be one of the following values:
vendor
the original flag set by the vendor is returned;
system
the flag is set/modified by a system-wide configuration;
user
the flag is set/modified by a user-specific configuration;
env the flag is set/modified by an environment-specific
configuration.
--query
Print any information that can be useful to explain the
behavior of the program: current vendor, relevant environment
variables, feature areas, state of all feature flags, whether
a feature is handled as a builtin default by the compiler, and
the compiler flags with their origin.
For example:
Vendor: Debian
Environment:
DEB_CFLAGS_SET=-O0 -Wall
Area: qa
Features:
bug=no
canary=no
Builtins:
Area: hardening
Features:
pie=no
Builtins:
pie=yes
Area: reproducible
Features:
timeless=no
Builtins:
Flag: CFLAGS
Value: -O0 -Wall
Origin: env
Flag: CPPFLAGS
Value: -D_FORTIFY_SOURCE=2
Origin: vendor
Support for Flag stanza since dpkg 1.19.0. Support for
Builtins field in Area stanza since dpkg 1.21.14.
--query-features area
Print the features enabled for a given area. If the feature
is handled (even if only on some architectures) as a builtin
default by the compiler, then a Builtin field is printed. See
the "FEATURE AREAS" section for more details about the
currently recognized areas. Exits with 0 if the area is known
otherwise exits with 1.
The output is in deb822(5) format, with one section per
feature. For example:
Feature: pie
Enabled: yes
Builtin: yes
Feature: stackprotector
Enabled: yes
Supported since dpkg 1.16.2. Support for Builtin field since
dpkg 1.21.14.
--help
Show the usage message and exit.
--version
Show the version and exit.
ASFLAGS
Options for the host assembler. Default value: empty.
Supported since dpkg 1.21.0.
CFLAGS
Options for the host C compiler. The default value set by the
vendor includes -g and the default optimization level (-O2
usually, or -O0 if the DEB_BUILD_OPTIONS environment variable
defines noopt).
CPPFLAGS
Options for the host C preprocessor. Default value: empty.
CXXFLAGS
Options for the host C++ compiler. Same as CFLAGS.
OBJCFLAGS
Options for the host Objective C compiler. Same as CFLAGS.
Supported since dpkg 1.17.7.
OBJCXXFLAGS
Options for the host Objective C++ compiler. Same as
CXXFLAGS.
Supported since dpkg 1.17.7.
DFLAGS
Options for the host D compiler (ldc or gdc).
Supported since dpkg 1.20.6.
FFLAGS
Options for the host Fortran 77 compiler. A subset of CFLAGS.
FCFLAGS
Options for the host Fortran 9x compiler. Same as FFLAGS.
Supported since dpkg 1.17.7.
LDFLAGS
Options passed to the host compiler when linking executables
or shared objects.
Note: It is not safe to pass this variable directly to ld(1),
but if the variable needs to be passed anyway, then these
options should be sanitized to allow only options known to
work. In general -Wl, -l and -L options should be safe, with
-Wl getting stripped and , in its arguments replaced with
spaces. But whether any sanitized option is safe to be passed
through, will depend on the intended semantics of the ld(1)
invocation.
Default value: empty.
ASFLAGS_FOR_BUILD
Options for the build assembler. Default value: empty.
Supported since dpkg 1.22.1.
CFLAGS_FOR_BUILD
Options for the build C compiler. The default value set by
the vendor includes -g and the default optimization level (-O2
usually, or -O0 if the DEB_BUILD_OPTIONS environment variable
defines noopt).
Supported since dpkg 1.22.1.
CPPFLAGS_FOR_BUILD
Options for the build C preprocessor. Default value: empty.
Supported since dpkg 1.22.1.
CXXFLAGS_FOR_BUILD
Options for the build C++ compiler. Same as CFLAGS_FOR_BUILD.
Supported since dpkg 1.22.1.
OBJCFLAGS_FOR_BUILD
Options for the build Objective C compiler. Same as
CFLAGS_FOR_BUILD.
Supported since dpkg 1.22.1.
OBJCXXFLAGS_FOR_BUILD
Options for the build Objective C++ compiler. Same as
CXXFLAGS_FOR_BUILD.
Supported since dpkg 1.22.1.
DFLAGS_FOR_BUILD
Options for the build D compiler (ldc or gdc).
Supported since dpkg 1.22.1.
FFLAGS_FOR_BUILD
Options for the build Fortran 77 compiler. A subset of
CFLAGS_FOR_BUILD.
Supported since dpkg 1.22.1.
FCFLAGS_FOR_BUILD
Options for the build Fortran 9x compiler. Same as
FFLAGS_FOR_BUILD.
Supported since dpkg 1.22.1.
LDFLAGS_FOR_BUILD
Options passed to the build compiler when linking executables
or shared objects.
Note: It is not safe to pass this variable directly to ld(1),
but if the variable needs to be passed anyway, then these
options should be sanitized to allow only options known to
work. In general -Wl, -l and -L options should be safe, with
-Wl getting stripped and , in its arguments replaced with
spaces. But whether any sanitized option is safe to be passed
through, will depend on the intended semantics of the ld(1)
invocation.
Default value: empty.
Supported since dpkg 1.22.1.
New flags might be added in the future if the need arises (for
example to support other languages).
Feature areas are currently vendor specific, and the ones
described below are only recognized on Debian and derivatives.
Each area feature can be enabled and disabled in the
DEB_BUILD_OPTIONS and DEB_BUILD_MAINT_OPTIONS environment
variable's area value with the ‘+’ and ‘-’ modifier. Following
the general syntax of these variables (described in
dpkg-buildpackage(1)), multiple feature areas can be specified
separated by spaces, where each get feature specifiers as
mandatory parameters after an equal sign (‘=’). The feature
specifiers are comma-separated and parsed from left to right,
where the settings within the same feature specifier override
previous ones, even if the feature specifiers are split across
multiple space-separated feature area settings for the same area.
For example, to enable the hardening “pie” feature and disable the
“fortify” feature you can do this in debian/rules:
export DEB_BUILD_MAINT_OPTIONS = hardening=+pie,-fortify
The special feature all (valid in any area) can be used to enable
or disable all area features at the same time. Thus disabling
everything in the hardening area and enabling only “format” and
“fortify” can be achieved with:
export DEB_BUILD_MAINT_OPTIONS = hardening=-all,+format,+fortify
Multiple feature areas can be set:
export DEB_BUILD_MAINT_OPTIONS = hardening=+pie abi=+lfs
The override behavior applies as much to the all special feature,
as to specific features, which should allow for composition. Thus
to enable “lfs” in the abi area, and only “pie” and “fortify” in
the hardening area, but “format” only when CONDITION is defined,
this could be done with:
export DEB_BUILD_MAINT_OPTIONS = hardening=-all,+pie,+format abi=+lfs
…
DEB_BUILD_MAINT_OPTIONS += hardening=+fortify
ifdef CONDITION
DEB_BUILD_MAINT_OPTIONS += hardening=-format
endif
abi
Several compile-time options (detailed below) can be used to
enable features that can change the ABI of a package, but cannot
be enabled by default due to backwards compatibility reasons
unless coordinated or checked individually.
lfs This setting enables Large File Support on 32-bit
architectures where their ABI does not include LFS by default,
by adding -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 to
CPPFLAGS.
Note: The getconf(1) interface to query LFS build flags, such
as LFS_CFLAGS or LFS_LDFLAGS, must not be used because this
interface does not support cross-building.
When this feature is enabled it will override the value from
the same feature in the future feature area.
Disabled by default.
Supported since dpkg 1.22.0.
time64
This setting enables 64-bit time_t support on 32-bit
architectures where their ABI does not include it by default,
by adding -D_TIME_BITS=64 to CPPFLAGS. This setting
automatically enables the lfs feature from the abi feature
area.
If the setting is enabled explicitly then it gets enabled on
all architectures including i386 but not hurd-i386 (where the
kernel does not have time64 interfaces), ignoring the binary
backwards compatibility default.
It is also enabled by default by gcc on the armel, armhf,
hppa, m68k, mips, mipsel, powerpc and sh4 Debian
architectures, where disabling the feature will add instead
-U_LARGEFILE_SOURCE -U_FILE_OFFSET_BITS -U_TIME_BITS to
CPPFLAGS.
Enabled by default except for i386 and hurd-i386 since dpkg
1.22.5.
Supported since dpkg 1.22.0.
future
Several compile-time options (detailed below) can be used to
enable features that should be enabled by default, but cannot due
to backwards compatibility reasons.
lfs This setting is now an alias for the lfs feature in the abi
area, use that instead. The feature from the abi area
overrides this setting.
Disabled by default.
Supported since dpkg 1.19.0.
qa
Several compile-time options (detailed below) can be used to help
detect problems in the source code or build system.
bug-implicit-func
This setting adds -Werror=implicit-function-declaration to
CFLAGS.
Enabled by default since dpkg 1.22.6.
Supported since dpkg 1.22.3.
bug This setting adds any warning option that reliably detects
problematic source code. The warnings are fatal. The only
currently supported flags are CFLAGS and CXXFLAGS with flags
set to -Werror=array-bounds, -Werror=clobbered,
-Werror=implicit-function-declaration and
-Werror=volatile-register-var.
This feature handles -Werror=implicit-function-declaration via
the bug-implicit-func feature, if that has not been specified.
Disabled by default.
Supported since dpkg 1.17.4.
canary
This setting adds dummy canary options to the build flags, so
that the build logs can be checked for how the build flags
propagate and to allow finding any omission of normal build
flag settings. The only currently supported flags are
CPPFLAGS, CFLAGS, OBJCFLAGS, CXXFLAGS and OBJCXXFLAGS with
flags set to -D__DEB_CANARY_flag_random-id__, and LDFLAGS set
to -Wl,-z,deb-canary-random-id.
Disabled by default.
Supported since dpkg 1.17.14.
optimize
Several compile-time options (detailed below) can be used to help
optimize a resulting binary. Note: Enabling all these options can
result in unreproducible binary artifacts.
Supported since dpkg 1.21.0.
lto This setting enables Link Time Optimization by adding
-flto=auto -ffat-lto-objects to CFLAGS, CXXFLAGS, OBJCFLAGS,
OBJCXXFLAGS, FFLAGS, FCFLAGS and LDFLAGS.
Disabled by default.
Supported since dpkg 1.21.0.
sanitize
Several compile-time options (detailed below) can be used to help
sanitize a resulting binary against memory corruptions, memory
leaks, use after free, threading data races and undefined behavior
bugs. Note: These options should not be used for production
builds as they can reduce reliability for conformant code, reduce
security or even functionality.
address
This setting adds -fsanitize=address to LDFLAGS and
-fsanitize=address -fno-omit-frame-pointer to CFLAGS and
CXXFLAGS.
Disabled by default.
Supported since dpkg 1.18.0.
thread
This setting adds -fsanitize=thread to CFLAGS, CXXFLAGS and
LDFLAGS.
Disabled by default.
Supported since dpkg 1.18.0.
leak
This setting adds -fsanitize=leak to LDFLAGS. It gets
automatically disabled if either the address or the thread
features are enabled, as they imply it.
Disabled by default.
Supported since dpkg 1.18.0.
undefined
This setting adds -fsanitize=undefined to CFLAGS, CXXFLAGS and
LDFLAGS.
Disabled by default.
Supported since dpkg 1.18.0.
hardening
Several compile-time options (detailed below) can be used to help
harden a resulting binary against memory corruption attacks, or
provide additional warning messages during compilation. Except as
noted below, these are enabled by default for architectures that
support them.
format
This setting adds -Wformat -Werror=format-security to CFLAGS,
CXXFLAGS, OBJCFLAGS and OBJCXXFLAGS. This will warn about
improper format string uses, and will fail when format
functions are used in a way that represent possible security
problems. At present, this warns about calls to printf and
scanf functions where the format string is not a string
literal and there are no format arguments, as in printf(foo);
instead of printf("%s", foo); This may be a security hole if
the format string came from untrusted input and contains ‘%n’.
Enabled by default.
Supported since dpkg 1.16.1.
fortify
This setting adds -D_FORTIFY_SOURCE=2 to CPPFLAGS. During
code generation the compiler knows a great deal of information
about buffer sizes (where possible), and attempts to replace
insecure unlimited length buffer function calls with
length-limited ones. This is especially useful for old,
crufty code. Additionally, format strings in writable memory
that contain ‘%n’ are blocked. If an application depends on
such a format string, it will need to be worked around.
Note that for this option to have any effect, the source must
also be compiled with -O1 or higher. If the environment
variable DEB_BUILD_OPTIONS contains noopt, then fortify
support will be disabled, due to new warnings being issued by
glibc 2.16 and later.
Enabled by default.
Supported since dpkg 1.16.1.
stackprotector
This setting adds -fstack-protector --param=ssp-buffer-size=4
to CFLAGS, CXXFLAGS, OBJCFLAGS, OBJCXXFLAGS, FFLAGS and
FCFLAGS. This adds safety checks against stack overwrites.
This renders many potential code injection attacks into
aborting situations. In the best case this turns code
injection vulnerabilities into denial of service or into
non-issues (depending on the application).
This feature requires linking against glibc (or another
provider of __stack_chk_fail), so needs to be disabled when
building with -nostdlib or -ffreestanding or similar.
Enabled by default if stackprotectorstrong is not in use.
Supported since dpkg 1.16.1.
stackprotectorstrong
This setting adds -fstack-protector-strong to CFLAGS,
CXXFLAGS, OBJCFLAGS, OBJCXXFLAGS, FFLAGS and FCFLAGS. This is
a stronger variant of stackprotector, but without significant
performance penalties.
This feature has the same requirements as stackprotector, and
in addition also requires gcc 4.9 and later.
Enabled by default. Disabling stackprotector will also
disable this setting.
Supported since dpkg 1.17.11.
stackclash
This setting adds -fstack-clash-protection on amd64, arm64,
armhf and armel to CFLAGS, CXXFLAGS, OBJCFLAGS, OBJCXXFLAGS,
FFLAGS and FCFLAGS. This adds code to prevent stack clash
style attacks.
Enabled by default.
Supported since dpkg 1.22.0.
branch
This setting adds -fcf-protection on amd64 and
-mbranch-protection=standard on arm64 to CFLAGS, CXXFLAGS,
OBJCFLAGS, OBJCXXFLAGS, FFLAGS and FCFLAGS. This adds branch
protection to indirect calls, jumps and returns to check
whether these are valid at run-time.
Enabled by default.
Supported since dpkg 1.22.0.
relro
This setting adds -Wl,-z,relro to LDFLAGS. During program
load, several ELF memory sections need to be written to by the
linker. This flags the loader to turn these sections
read-only before turning over control to the program. Most
notably this prevents GOT overwrite attacks. If this option
is disabled, bindnow will become disabled as well.
Enabled by default.
Supported since dpkg 1.16.1.
bindnow
This setting adds -Wl,-z,now to LDFLAGS. During program load,
all dynamic symbols are resolved, allowing for the entire PLT
to be marked read-only (due to relro above). The option
cannot become enabled if relro is not enabled.
Disabled by default.
Supported since dpkg 1.16.1.
pie This setting adds the required options to enable or disable
PIE via gcc specs files, if needed, depending on whether gcc
injects on that architecture the flags by itself or not. When
the setting is enabled and gcc injects the flags, it adds
nothing. When the setting is enabled and gcc does not inject
the flags, it adds -fPIE (via
/usr/local/share/dpkg/pie-compiler.specs) to CFLAGS, CXXFLAGS,
OBJCFLAGS, OBJCXXFLAGS, FFLAGS and FCFLAGS, and -fPIE -pie
(via /usr/local/share/dpkg/pie-link.specs) to LDFLAGS. When
the setting is disabled and gcc injects the flags, it adds
-fno-PIE (via /usr/local/share/dpkg/no-pie-compile.specs) to
CFLAGS, CXXFLAGS, OBJCFLAGS, OBJCXXFLAGS, FFLAGS and FCFLAGS,
and -fno-PIE -no-pie (via
/usr/local/share/dpkg/no-pie-link.specs) to LDFLAGS.
Position Independent Executable (PIE) is needed to take
advantage of Address Space Layout Randomization (ASLR),
supported by some kernel versions. While ASLR can already be
enforced for data areas in the stack and heap (brk and mmap),
the code areas must be compiled as position-independent.
Shared libraries already do this (-fPIC), so they gain ASLR
automatically, but binary .text regions need to be built as
PIE to gain ASLR. When this happens, ROP (Return Oriented
Programming) attacks are much harder since there are no static
locations to bounce off of during a memory corruption attack.
PIE is not compatible with -fPIC, so in general care must be
taken when building shared objects. But because the PIE flags
emitted get injected via gcc specs files, it should always be
safe to unconditionally set them regardless of the object type
being compiled or linked.
Static libraries can be used by programs or other shared
libraries. Depending on the flags used to compile all the
objects within a static library, these libraries will be
usable by different sets of objects:
none
Cannot be linked into a PIE program, nor a shared library.
-fPIE
Can be linked into any program, but not a shared library
(recommended).
-fPIC
Can be linked into any program and shared library.
If there is a need to set these flags manually, bypassing the
gcc specs injection, there are several things to take into
account. Unconditionally and explicitly passing -fPIE, -fpie
or -pie to a build-system using libtool is safe as these flags
will get stripped when building shared libraries. Otherwise
on projects that build both programs and shared libraries you
might need to make sure that when building the shared
libraries -fPIC is always passed last (so that it overrides
any previous -PIE) to compilation flags such as CFLAGS, and
-shared is passed last (so that it overrides any previous
-pie) to linking flags such as LDFLAGS. Note: This should not
be needed with the default gcc specs machinery.
Additionally, since PIE is implemented via a general register,
some register starved architectures (but not including i386
anymore since optimizations implemented in gcc >= 5) can see
performance losses of up to 15% in very text-segment-heavy
application workloads; most workloads see less than 1%.
Architectures with more general registers (e.g. amd64) do not
see as high a worst-case penalty.
No global default since dpkg 1.18.23, as it is enabled by
default now by gcc on the amd64, arm64, armel, armhf,
hurd-i386, i386, mips, mipsel, mips64el, powerpc, ppc64,
ppc64el, riscv64, s390x, sparc and sparc64 Debian
architectures.
Supported since dpkg 1.16.1.
reproducible
The compile-time options detailed below can be used to help
improve build reproducibility or provide additional warning
messages during compilation. Except as noted below, these are
enabled by default for architectures that support them.
timeless
This setting adds -Wdate-time to CPPFLAGS. This will cause
warnings when the __TIME__, __DATE__ and __TIMESTAMP__ macros
are used.
Enabled by default.
Supported since dpkg 1.17.14.
fixfilepath
This setting adds -ffile-prefix-map=BUILDPATH=. to CFLAGS,
CXXFLAGS, OBJCFLAGS, OBJCXXFLAGS, FFLAGS and FCFLAGS where
BUILDPATH is set to the top-level directory of the package
being built. This has the effect of removing the build path
from any generated file.
If both fixdebugpath and fixfilepath are set, this option
takes precedence, because it is a superset of the former.
Note: If the build process captures the build flags into the
resulting built objects, that will make the package
unreproducible. And while disabling this option might make
some of the objects reproducible again this would also require
disabling fixdebugpath, which might make any generated debug
symbols objects unreproducible. The ideal fix is to stop
capturing build flags.
Enabled by default.
Supported since dpkg 1.19.1.
fixdebugpath
This setting adds -fdebug-prefix-map=BUILDPATH=. to CFLAGS,
CXXFLAGS, OBJCFLAGS, OBJCXXFLAGS, FFLAGS and FCFLAGS where
BUILDPATH is set to the top-level directory of the package
being built. This has the effect of removing the build path
from any generated debug symbols.
Note: This feature has similar reproducible properties as
fixfilepath.
Enabled by default.
Supported since dpkg 1.18.5.
There are 2 sets of environment variables doing the same
operations, the first one (DEB_flag_op) should never be used
within debian/rules. It's meant for any user that wants to
rebuild the source package with different build flags. The second
set (DEB_flag_MAINT_op) should only be used in debian/rules by
package maintainers to change the resulting build flags.
DEB_flag_SET
DEB_flag_MAINT_SET
This variable can be used to force the value returned for the
given flag.
Support for DEB_flag_MAINT_SET since dpkg 1.16.1.
DEB_flag_STRIP
DEB_flag_MAINT_STRIP
This variable can be used to provide a space separated list of
options that will be stripped from the set of flags returned
for the given flag.
Supported since dpkg 1.16.1.
DEB_flag_APPEND
DEB_flag_MAINT_APPEND
This variable can be used to append supplementary options to
the value returned for the given flag.
Support for DEB_flag_MAINT_APPEND since dpkg 1.16.1.
DEB_flag_PREPEND
DEB_flag_MAINT_PREPEND
This variable can be used to prepend supplementary options to
the value returned for the given flag.
Supported since dpkg 1.16.1.
DEB_BUILD_OPTIONS
DEB_BUILD_MAINT_OPTIONS
These variables can be used by a user or maintainer to
disable/enable various area features that affect build flags.
The DEB_BUILD_MAINT_OPTIONS variable overrides any setting in
the DEB_BUILD_OPTIONS feature areas. See the "FEATURE AREAS"
section for details.
Some build profiles might currently require their counterpart
to also be included in the build options, the list of such
build profiles is vendor specific. For more information about
build profiles, see dpkg-buildpackage(1).
Support for DEB_BUILD_MAINT_OPTIONS since dpkg 1.16.1.
DEB_VENDOR
This setting defines the current vendor. If not set, it will
discover the current vendor by reading
/usr/local/etc/dpkg/origins/default.
DEB_BUILD_PATH
This variable sets the build path to use in features such as
fixdebugpath so that they can be controlled by the caller.
This variable is currently Debian and derivatives-specific.
Supported since dpkg 1.18.8.
DEB_HOST_ARCH
Sets the host architecture. This affects the build flags that
are emitted, which is typically relevant when cross-compiling,
where DEB_HOST_ARCH is different to DEB_BUILD_ARCH.
DPKG_COLORS
Sets the color mode. The currently accepted values are: auto
(default), always and never.
Supported since dpkg 1.18.5.
DPKG_NLS
If set, it will be used to decide whether to activate Native
Language Support, also known as internationalization (or i18n)
support. The accepted values are: 0 and 1 (default).
Supported since dpkg 1.19.0.
Configuration files
/usr/local/etc/dpkg/buildflags.conf
System wide configuration file.
$XDG_CONFIG_HOME/dpkg/buildflags.conf
$HOME/.config/dpkg/buildflags.conf
User configuration file.
Packaging support
/usr/local/share/dpkg/buildflags.mk
Makefile snippet that loads (and optionally exports) all flags
supported by dpkg-buildflags into variables.
Supported since dpkg 1.16.1.
/usr/local/share/dpkg/buildtools.mk
Makefile snippet that sets suitable host and build tools (and
optionally exports them) into variables.
Supported since dpkg 1.19.0.
To pass build flags to a build command in a Makefile:
$(MAKE) $(shell dpkg-buildflags --export=cmdline)
./configure $(shell dpkg-buildflags --export=cmdline)
To set build flags in a shell script or shell fragment, eval can
be used to interpret the output and to export the flags in the
environment:
eval "$(dpkg-buildflags --export=sh)" && make
or to set the positional parameters to pass to a command:
eval "set -- $(dpkg-buildflags --export=cmdline)"
for dir in a b c; do (cd $dir && ./configure "$@" && make); done
Usage in debian/rules
You should call dpkg-buildflags or include buildflags.mk from the
debian/rules file to obtain the needed build flags to pass to the
build system. Note that older versions of dpkg-buildpackage
(before dpkg 1.16.1) exported these flags automatically. However,
you should not rely on this, since this breaks manual invocation
of debian/rules.
For packages with autoconf-like build systems, you can pass the
relevant options to configure or make(1) directly, as shown above.
For other build systems, or when you need more fine-grained
control about which flags are passed where, you can use --get. Or
you can include buildflags.mk instead, which takes care of calling
dpkg-buildflags and storing the build flags in make variables.
If you want to export all buildflags into the environment (where
they can be picked up by your build system):
DPKG_EXPORT_BUILDFLAGS = 1
include /usr/local/share/dpkg/buildflags.mk
For some extra control over what is exported, you can manually
export the variables (as none are exported by default):
include /usr/local/share/dpkg/buildflags.mk
export CPPFLAGS CFLAGS LDFLAGS
And you can of course pass the flags to commands manually:
include /usr/local/share/dpkg/buildflags.mk
build-arch:
$(CC) -o hello hello.c $(CPPFLAGS) $(CFLAGS) $(LDFLAGS)
This page is part of the dpkg (Debian Package Manager) project.
Information about the project can be found at
⟨https://wiki.debian.org/Teams/Dpkg/⟩. If you have a bug report
for this manual page, see
⟨http://bugs.debian.org/cgi-bin/pkgreport.cgi?src=dpkg⟩. This
page was obtained from the project's upstream Git repository ⟨git
clone https://git.dpkg.org/git/dpkg/dpkg.git⟩ on 2026-08-03. (At
that time, the date of the most recent commit that was found in
the repository was 2026-08-01.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
1.23.7-216-gff7e9 2026-03-07 dpkg-buildflags(1)
Pages that refer to this page: dpkg-buildpackage(1), deb-src-rules(5), debhelper(7)
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