utils.bzl

skylark utils for packaging tasks

Some handy functions for common packaging tasks for Skylark based buildsystems eg. Buck and Bazel.

extract(rule, path)

extracts file from a given rule

Example

load('//:utils.bzl', 'extract')

genrule(
  name = 'gen',
  out = 'out',
  cmd = 'mkdir $OUT && touch $OUT/foo.h && touch $OUT/foo.cpp'
)

cxx_library(
  name = 'foo',
  srcs = [extract(':gen', 'foo.cpp')]
  exported_headers = {
    'foo.h' : extract(':gen', 'foo.h')
  }
)

extractFolder(rule, path)

genrule(
  name = 'gen',
  out = 'out',
  cmd = 'mkdir -p $OUT/include/foo && touch $OUT/include/foo/foo.h && touch $OUT/include/foo/bar.h'
)

prebuilt_cxx_library(
  name = 'foo',
  header_only = True,
  header_dirs = [
    extractFolder(':gen', 'include')
  ]
)

pkgconfig(name, find, search)

generates a prebuilt_cxx_library using pkgconfig.

find specifies the pkgconfig library name. As per convention it will look for *.pc

search specifies the searchPath. It can be a macro, relative or absolute paths.

We advise against using absolute paths eg. /usr/lib to fetch system-libraries as this will make builds irreproducible.

Example

genrule(
  name = 'gen',
  out = 'out',
  cmd = '...'
)

pkgconfig(
  name = 'mylib',
  find = 'mylib-c'
  search = '$(location :gen)/lib/pkgconfig'
)

cmake(name, srcs, prefix = 'ROOT', options = [], targets = [])

creates a wrapper for cmake builds.

srcs all files required for cmake to run. The more precise you are the better as it will improve unnecessary rebuilts.

prefix defines the prefix that will be used when an install is performed. The install folder can then be used for extracting indidual files and folders.

options extra cmake options that will be supplied to the cmake configure call.

targets set of build targets. No build is performed if not specified. This comes handy if you only need the generated config.h.

A common target is install that will create a distributatble version of the library.

Examples

Version Header-Only Extraction

cmake(
  name = 'config',
  srcs = glob(['CMakeLists.txt', 'version.cpp.in', 'src/**/*.cpp'])  
)

cxx_library(
  name = 'lib',
  header_namespace = '',
  srcs = glob(['srcs/**/*.cpp']) + [extract(':config', 'version.cpp')],
  exported_headers = subdir_glob([
    ('include', '**/*.h')
  ])
)

Full CMake Build - Xerces

cmake(
  name = 'xerces-cmake',
  prefix = 'dist',
  targets = ['install'],
  srcs = glob([
    'cmake/**',
    'config/**',
    'doc/**',
    'src/**',
    'samples/**',
    'scripts/**',
    'tools/**',
    'tests/**',
    '*.txt',
    '*.in',
    '*.ac'
  ])
)

prebuilt_cxx_library(
  name = 'xerces',
  header_namespace = '',
  preferred_linkage = 'shared',
  shared_lib = extract(':xerces-cmake', 'dist/lib/libxerces-c.so'),
  header_dirs = [ 
    extractFolder(':xerces-cmake', 'dist/include')
  ],
)

cxx_binary(
  name = 'count',
  srcs = ['samples/src/DOMCount/DOMCount.cpp'],
  headers = {'DOMCount.hpp': 'samples/src/DOMCount/DOMCount.hpp'},
  deps = [':xerces']
)

subdir_glob

see https://buckbuild.com/function/subdir_glob.html#content