dpkg-buildflags(1) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | COMMANDS | SUPPORTED FLAGS | FEATURE AREAS | ENVIRONMENT | FILES | EXAMPLES | COLOPHON

dpkg-buildflags(1)             dpkg suite             dpkg-buildflags(1)

NAME         top

       dpkg-buildflags - returns build flags to use during package build

SYNOPSIS         top

       dpkg-buildflags [option...] [command]

DESCRIPTION         top

       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.  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         top

       --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=2
            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).  The only
           currently recognized areas on Debian and derivatives are
           future, qa, reproducible, sanitize and hardening, see the
           FEATURE AREAS section for more details.  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         top

       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.

       LDFLAGS
           Options passed to the host compiler when linking executables
           or shared objects (if the linker is called directly, then -Wl
           and , have to be stripped from these options). 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 (if the linker is called directly, then -Wl
           and , have to be stripped from these options).  Default
           value: empty.  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         top

       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.  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

   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; disabled by default) 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
           as it requires it.

   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 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.

       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.

   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; disabled by default) enables
           Link Time Optimization by adding -flto=auto -ffat-lto-objects
           to CFLAGS, CXXFLAGS, OBJCFLAGS, OBJCXXFLAGS, FFLAGS, FCFLAGS
           and LDFLAGS.

   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=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.

       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, kfreebsd-amd64,
           kfreebsd-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/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.

   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=.  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.

ENVIRONMENT         top

       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.

       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 (since dpkg 1.18.8) to use
           in features such as fixdebugpath so that they can be
           controlled by the caller.  This variable is currently Debian
           and derivatives-specific.

       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         top

   Configuration files
       /usr/local/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/local/share/dpkg/buildflags.mk
           Makefile snippet that will load (and optionally export) all
           flags supported by dpkg-buildflags into variables (since dpkg
           1.16.1).

EXAMPLES         top

       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)

COLOPHON         top

       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 2023-12-22.  (At
       that time, the date of the most recent commit that was found in
       the repository was 2023-12-18.)  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

1.22.1-2-gddb42                2023-10-30             dpkg-buildflags(1)

Pages that refer to this page: dpkg-buildpackage(1)deb-src-rules(5)debhelper(7)