683b7d7a3f
We use pkg-config where we can, which generally replaces libtool at a higher level and does not have the same downsides as libtool. These archives sit in our depends tree with no purpose and pollute the final bitcoin build with massive overlinking.
183 lines
6.7 KiB
Markdown
183 lines
6.7 KiB
Markdown
Each recipe consists of 3 main parts: defining identifiers, setting build
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variables, and defining build commands.
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The package "mylib" will be used here as an example
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General tips:
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- mylib_foo is written as $(package)_foo in order to make recipes more similar.
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- Secondary dependency packages relative to the bitcoin binaries/libraries (i.e.
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those not in `ALLOWED_LIBRARIES` in `contrib/devtools/symbol-check.py`) don't
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need to be shared and should be built statically whenever possible. See
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[below](#secondary-dependencies) for more details.
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## Identifiers
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Each package is required to define at least these variables:
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$(package)_version:
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Version of the upstream library or program. If there is no version, a
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placeholder such as 1.0 can be used.
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$(package)_download_path:
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Location of the upstream source, without the file-name. Usually http, https
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or ftp. Secure transmission options like https should be preferred if
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available.
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$(package)_file_name:
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The upstream source filename available at the download path.
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$(package)_sha256_hash:
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The sha256 hash of the upstream file
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These variables are optional:
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$(package)_build_subdir:
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cd to this dir before running configure/build/stage commands.
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$(package)_download_file:
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The file-name of the upstream source if it differs from how it should be
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stored locally. This can be used to avoid storing file-names with strange
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characters.
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$(package)_dependencies:
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Names of any other packages that this one depends on.
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$(package)_patches:
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Filenames of any patches needed to build the package
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$(package)_extra_sources:
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Any extra files that will be fetched via $(package)_fetch_cmds. These are
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specified so that they can be fetched and verified via 'make download'.
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## Build Variables:
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After defining the main identifiers, build variables may be added or customized
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before running the build commands. They should be added to a function called
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$(package)_set_vars. For example:
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define $(package)_set_vars
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...
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endef
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Most variables can be prefixed with the host, architecture, or both, to make
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the modifications specific to that case. For example:
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Universal: $(package)_cc=gcc
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Linux only: $(package)_linux_cc=gcc
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x86_64 only: $(package)_x86_64_cc = gcc
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x86_64 linux only: $(package)_x86_64_linux_cc = gcc
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These variables may be set to override or append their default values.
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$(package)_cc
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$(package)_cxx
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$(package)_objc
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$(package)_objcxx
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$(package)_ar
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$(package)_ranlib
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$(package)_libtool
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$(package)_nm
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$(package)_cflags
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$(package)_cxxflags
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$(package)_ldflags
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$(package)_cppflags
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$(package)_config_env
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$(package)_build_env
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$(package)_stage_env
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$(package)_build_opts
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$(package)_config_opts
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The *_env variables are used to add environment variables to the respective
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commands.
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Many variables respect a debug/release suffix as well, in order to use them for
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only the appropriate build config. For example:
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$(package)_cflags_release = -O3
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$(package)_cflags_i686_debug = -g
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$(package)_config_opts_release = --disable-debug
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These will be used in addition to the options that do not specify
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debug/release. All builds are considered to be release unless DEBUG=1 is set by
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the user. Other variables may be defined as needed.
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## Build commands:
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For each build, a unique build dir and staging dir are created. For example,
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`work/build/mylib/1.0-1adac830f6e` and `work/staging/mylib/1.0-1adac830f6e`.
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The following build commands are available for each recipe:
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$(package)_fetch_cmds:
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Runs from: build dir
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Fetch the source file. If undefined, it will be fetched and verified
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against its hash.
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$(package)_extract_cmds:
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Runs from: build dir
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Verify the source file against its hash and extract it. If undefined, the
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source is assumed to be a tarball.
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$(package)_preprocess_cmds:
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Runs from: build dir/$(package)_build_subdir
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Preprocess the source as necessary. If undefined, does nothing.
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$(package)_config_cmds:
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Runs from: build dir/$(package)_build_subdir
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Configure the source. If undefined, does nothing.
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$(package)_build_cmds:
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Runs from: build dir/$(package)_build_subdir
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Build the source. If undefined, does nothing.
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$(package)_stage_cmds:
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Runs from: build dir/$(package)_build_subdir
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Stage the build results. If undefined, does nothing.
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The following variables are available for each recipe:
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$(1)_staging_dir: package's destination sysroot path
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$(1)_staging_prefix_dir: prefix path inside of the package's staging dir
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$(1)_extract_dir: path to the package's extracted sources
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$(1)_build_dir: path where configure/build/stage commands will be run
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$(1)_patch_dir: path where the package's patches (if any) are found
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Notes on build commands:
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For packages built with autotools, $($(package)_autoconf) can be used in the
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configure step to (usually) correctly configure automatically. Any
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$($(package)_config_opts) will be appended.
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Most autotools projects can be properly staged using:
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$(MAKE) DESTDIR=$($(package)_staging_dir) install
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## Build outputs:
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In general, the output of a depends package should not contain any libtool
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archives. Instead, the package should output `.pc` (`pkg-config`) files where
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possible.
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From the [Gentoo Wiki entry](https://wiki.gentoo.org/wiki/Project:Quality_Assurance/Handling_Libtool_Archives):
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> Libtool pulls in all direct and indirect dependencies into the .la files it
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> creates. This leads to massive overlinking, which is toxic to the Gentoo
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> ecosystem, as it leads to a massive number of unnecessary rebuilds.
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## Secondary dependencies:
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Secondary dependency packages relative to the bitcoin binaries/libraries (i.e.
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those not in `ALLOWED_LIBRARIES` in `contrib/devtools/symbol-check.py`) don't
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need to be shared and should be built statically whenever possible. This
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improves general build reliability as illustrated by the following example:
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When linking an executable against a shared library `libprimary` that has its
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own shared dependency `libsecondary`, we may need to specify the path to
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`libsecondary` on the link command using the `-rpath/-rpath-link` options, it is
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not sufficient to just say `libprimary`.
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For us, it's much easier to just link a static `libsecondary` into a shared
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`libprimary`. Especially because in our case, we are linking against a dummy
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`libprimary` anyway that we'll throw away. We don't care if the end-user has a
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static or dynamic `libseconday`, that's not our concern. With a static
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`libseconday`, when we need to link `libprimary` into our executable, there's no
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dependency chain to worry about as `libprimary` has all the symbols.
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