RPM provides a rich set of macros to make package maintenance simpler and consistent across packages. For example, it includes a list of default path definitions which are used by the build system macros, and definitions for RPM package build specific directories. They usually should be used instead of hard-coded directories. It also provides the default set of compiler flags as macros, which should be used when compiling manually and not relying on a build system.
Getting and setting Macros on the command line
It’s possible to let RPM evaluate arbitrary strings containing macros
on the command line by running rpm --eval on the command line:
$ rpm --eval "some text printed on %{_arch}"
some text printed on x86_64
Additionally, values for macros can be temporarily provided (and overridden)
by providing command line options to rpm and rpmbuild:
$ rpm --define "test Hello, World!" --eval "%{test}"
Hello, World!
Macros for paths set and used by build systems
The macros for build system invocations
(for example, %configure, %cmake, or %meson)
use the values defined by RPM to set installation paths for packages.
So, it’s usually preferable to not hard-code these paths in spec files either,
but use the same macros for consistency.
The values for these macros can be inspected
by looking at /usr/lib/rpm/platform/*/macros for the respective platform.
The following table lists macros which are widely used in fedora .spec files.
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can be defined to |
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default: |
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Some seldomly used macros are listed below for completeness.
Old .spec files might still use them,
and there might be cases where they are still needed.
| macro | definition | comment |
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default: |
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default: |
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default: |
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old misspelling, provided for compatiblity |
Macros set for the RPM (and SRPM) build process
RPM also exposes the locations of several directories that are relevant to the package build process via macros.
The only macro that’s widely used in .spec files is %{buildroot},
which points to the root of the installation target directory.
It is used for setting DESTDIR in the package’s %install step.
The other macros are usually only used outside .spec files.
For example, they are set by fedpkg to override the default directories.
| macro | definition | comment |
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same as |
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Macros providing compiler and linker flags
The default build flags for binaries on fedora are also available via macros.
They are used by the build system macros to setup the build environment,
so it is usually not necessary to use them directly — except, for example, when doing bare bones compilation with gcc directly.
The set of flags listed below reflects the current state of fedora 28
on a x86_64 machine, as defined in the file /usr/lib/rpm/redhat/macros.
The %{optflags} macro contains flags that determine CFLAGS, CXXFLAGS,
FFLAGS, etc. — the %{__global_cflags} macro evaluates to the same string.
The current definitions of these values
can be found in the redhat-rpm-macros package, in the build flags documentation.
$ rpm --eval "%{optflags}"
-O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -fexceptions -fstack-protector-strong -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection
The value of the LDFLAGS environment variable set by build systems
is determined by the %{build_flags} macro:
$ rpm -E "%{build_ldflags}"
-Wl,-z,relro -Wl,-z,now -specs=/usr/lib/rpm/redhat/redhat-hardened-ld