Manual: dpkg-buildflags
dpkg-buildflags(1) dpkg suite dpkg-buildflags(1)
NAME
dpkg-buildflags - returns build flags to use during package build
SYNOPSIS
dpkg-buildflags [option...] [command]
DESCRIPTION
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 /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. 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. 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.
COMMANDS
--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 (since dpkg
1.16.5): 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.
--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 (since
dpkg 1.17.0). The flag values are quoted in shell syntax.
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 (since dpkg 1.21.14), and the compiler flags with
their origin (since dpkg 1.19.0).
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=3
Origin: vendor
--query-features area
Print the features enabled for a given area (since dpkg 1.16.2). If the feature is handled (even
if only on some architectures) as a builtin default by the compiler, then a Builtin field is
printed (since dpkg 1.21.14). 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 RFC822 format, with one section per feature. For example:
Feature: pie
Enabled: yes
Builtin: yes
Feature: stackprotector
Enabled: yes
--help
Show the usage message and exit.
--version
Show the version and exit.
SUPPORTED FLAGS
ASFLAGS
Options for the host assembler. Default value: empty. 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. Since dpkg 1.17.7.
OBJCXXFLAGS
Options for the host Objective C++ compiler. Same as CXXFLAGS. Since dpkg 1.17.7.
DFLAGS
Options for the host D compiler (ldc or gdc). 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. Since dpkg 1.17.7.
RUSTFLAGS
Options for the host Rust compiler (rustc). Since dpkg 1.22.6ubuntu12.
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. 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). Since dpkg 1.22.1.
CPPFLAGS_FOR_BUILD
Options for the build C preprocessor. Default value: empty. Since dpkg 1.22.1.
CXXFLAGS_FOR_BUILD
Options for the build C++ compiler. Same as CFLAGS_FOR_BUILD. Since dpkg 1.22.1.
OBJCFLAGS_FOR_BUILD
Options for the build Objective C compiler. Same as CFLAGS_FOR_BUILD. Since dpkg 1.22.1.
OBJCXXFLAGS_FOR_BUILD
Options for the build Objective C++ compiler. Same as CXXFLAGS_FOR_BUILD. Since dpkg 1.22.1.
DFLAGS_FOR_BUILD
Options for the build D compiler (ldc or gdc). Since dpkg 1.22.1.
FFLAGS_FOR_BUILD
Options for the build Fortran 77 compiler. A subset of CFLAGS_FOR_BUILD. Since dpkg 1.22.1.
FCFLAGS_FOR_BUILD
Options for the build Fortran 9x compiler. Same as FFLAGS_FOR_BUILD. 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.
Since dpkg 1.22.1.
RUSTFLAGS_FOR_BUILD
Options for the build Rust compiler (rustc). Since dpkg 1.22.6ubuntu12.
New flags might be added in the future if the need arises (for example to support other languages).
FEATURE AREAS
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 (since dpkg 1.22.0; disabled by default) 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.
When this feature is enabled it will override the value from the same feature in the future
feature area.
time64
This setting (since dpkg 1.22.0; enabled by default except for i386 and hurd-i386 since dpkg
1.22.5) 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.
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 (since dpkg 1.19.0; disabled by default) is now an alias for the lfs feature in the
abi area, use that instead. The feature from the abi area overrides this setting.
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 (since dpkg 1.22.3; enabled by default since dpkg 1.22.6) adds
-Werror=implicit-function-declaration to CFLAGS.
bug This setting (since dpkg 1.17.4; disabled by default) 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.
canary
This setting (since dpkg 1.17.14; disabled by default) 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.
elfpackagemetadata
This setting (since dpkg 1.22.6ubuntu11; enabled by default) adds an ELF note containing package
metadata to every ELF binary being built. If the $DEB_BUILD_DEBUG_INFO_URL environment variable
is defined, it will be used to include the value as a debuginfod URL. This follows the
specification defined at: https://systemd.io/ELF_PACKAGE_METADATA/
optimize
Several compile-time options (detailed below) can be used to help optimize a resulting binary (since
dpkg 1.21.0). Note: Enabling all these options can result in unreproducible binary artifacts.
lto This setting (since dpkg 1.21.0) enables Link Time Optimization by adding -flto=auto
-ffat-lto-objects to CFLAGS, CXXFLAGS, OBJCFLAGS, OBJCXXFLAGS, FFLAGS, FCFLAGS and LDFLAGS.
Note: this option is enabled by default in Ubuntu on all 64bit architectures, except for riscv64.
A list of packages with LTO disabled by default is maintained in
/usr/share/lto-disabled-list/lto-disabled-list, provided by the lto-disabled-list package.
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 (since dpkg 1.18.0; disabled by default) adds -fsanitize=address to LDFLAGS and
-fsanitize=address -fno-omit-frame-pointer to CFLAGS and CXXFLAGS.
thread
This setting (since dpkg 1.18.0; disabled by default) adds -fsanitize=thread to CFLAGS, CXXFLAGS
and LDFLAGS.
leak
This setting (since dpkg 1.18.0; disabled by default) adds -fsanitize=leak to LDFLAGS. It gets
automatically disabled if either the address or the thread features are enabled, as they imply
it.
undefined
This setting (since dpkg 1.18.0; disabled by default) adds -fsanitize=undefined to CFLAGS,
CXXFLAGS and LDFLAGS.
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 (since dpkg 1.16.1; enabled by default) 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’.
fortify
This setting (since dpkg 1.16.1; enabled by default) adds -D_FORTIFY_SOURCE=3 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.
stackprotector
This setting (since dpkg 1.16.1; enabled by default if stackprotectorstrong is not in use) 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.
stackprotectorstrong
This setting (since dpkg 1.17.11; enabled by default) adds -fstack-protector-strong to CFLAGS,
CXXFLAGS, OBJCFLAGS, OBJCXXFLAGS, FFLAGS and FCFLAGS. This is a stronger variant of
stackprotector, but without significant performance penalties.
Disabling stackprotector will also disable this setting.
This feature has the same requirements as stackprotector, and in addition also requires gcc 4.9
and later.
stackclash
This setting (since dpkg 1.22.0; enabled by default) 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.
branch
This setting (since dpkg 1.22.0; enabled by default) 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.
relro
This setting (since dpkg 1.16.1; enabled by default) 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.
bindnow
This setting (since dpkg 1.16.1; disabled by default) 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.
pie This setting (since dpkg 1.16.1; with 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) 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/share/dpkg/pie-compiler.specs) to CFLAGS, CXXFLAGS, OBJCFLAGS,
OBJCXXFLAGS, FFLAGS and FCFLAGS, and -fPIE -pie (via /usr/share/dpkg/pie-link.specs) to LDFLAGS.
When the setting is disabled and gcc injects the flags, it adds -fno-PIE (via
/usr/share/dpkg/no-pie-compile.specs) to CFLAGS, CXXFLAGS, OBJCFLAGS, OBJCXXFLAGS, FFLAGS and
FCFLAGS, and -fno-PIE -no-pie (via /usr/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.
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 (since dpkg 1.17.14; enabled by default) adds -Wdate-time to CPPFLAGS. This will
cause warnings when the __TIME__, __DATE__ and __TIMESTAMP__ macros are used.
fixfilepath
This setting (since dpkg 1.19.1; enabled by default) 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.
fixdebugpath
This setting (since dpkg 1.18.5; enabled by default) adds
-fdebug-prefix-map=BUILDPATH=/usr/src/PKGNAME-PKGVER 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 and replacing it
with /usr/src/PKGNAME-PKGVER, where PKGNAME is the source package name and PKGVER is the source
package version.
Note: This feature has similar reproducible properties as fixfilepath.
ENVIRONMENT
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 (since dpkg 1.16.1)
This variable can be used to force the value returned for the given flag.
DEB_flag_STRIP (since dpkg 1.16.1)
DEB_flag_MAINT_STRIP (since dpkg 1.16.1)
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.
DEB_flag_APPEND
DEB_flag_MAINT_APPEND (since dpkg 1.16.1)
This variable can be used to append supplementary options to the value returned for the given
flag.
DEB_flag_PREPEND (since dpkg 1.16.1)
DEB_flag_MAINT_PREPEND (since dpkg 1.16.1)
This variable can be used to prepend supplementary options to the value returned for the given
flag.
DEB_BUILD_OPTIONS
DEB_BUILD_MAINT_OPTIONS (since dpkg 1.16.1)
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).
DEB_VENDOR
This setting defines the current vendor. If not set, it will discover the current vendor by
reading /etc/dpkg/origins/default.
DEB_BUILD_PATH
This variable sets the build path (since dpkg 1.18.8) to use in features such as fixfilepath so
that they can be controlled by the caller. This variable is currently Debian and derivatives-
specific.
DEB_BUILD_DEBUGPATH
This variable sets the debug build path (since dpkg 1.21.9ubuntu2) to use in features such as
fixdebugpath so that they can be controlled by the caller. This variable is currently Ubuntu-
specific.
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 (since dpkg 1.18.5). The currently accepted values are: auto (default),
always and never.
DPKG_NLS
If set, it will be used to decide whether to activate Native Language Support, also known as
internationalization (or i18n) support (since dpkg 1.19.0). The accepted values are: 0 and 1
(default).
FILES
Configuration files
/etc/dpkg/buildflags.conf
System wide configuration file.
$XDG_CONFIG_HOME/dpkg/buildflags.conf or
$HOME/.config/dpkg/buildflags.conf
User configuration file.
Packaging support
/usr/share/dpkg/buildflags.mk
Makefile snippet that loads (and optionally exports) all flags supported by dpkg-buildflags into
variables (since dpkg 1.16.1).
/usr/share/dpkg/buildtools.mk
Makefile snippet that sets suitable host and build tools (and optionally exports them) into
variables (since dpkg 1.19.0).
LTO exclusion list
/usr/share/lto-disabled-list/lto-disabled-list
A text file, listing source packages and architectures where LTO should not be enabled, allowing
the package to build without modifying it.
EXAMPLES
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/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/share/dpkg/buildflags.mk
export CPPFLAGS CFLAGS LDFLAGS
And you can of course pass the flags to commands manually:
include /usr/share/dpkg/buildflags.mk
build-arch:
$(CC) -o hello hello.c $(CPPFLAGS) $(CFLAGS) $(LDFLAGS)
1.23.7 2026-03-31 dpkg-buildflags(1)