Class: Rubycc::Pkgconf::SystemPathFilter

Inherits:
Object
  • Object
show all
Defined in:
lib/rubycc/pkgconf/system_path_filter.rb

Overview

Drops the -I<dir>/-L<dir> tokens whose directory the toolchain already searches on its own. pkg-config suppresses those in its --cflags/--libs output (emitting them would let a package silently reorder the compiler's or linker's default search order), so a shim that kept them would disagree with the real tool on the most common packages of all: this environment's zlib.pc alone carries -I/usr/include and -L${libdir}.

The two escape hatches are the ones the environment exposes: PKG_CONFIG_ALLOW_SYSTEM_CFLAGS / PKG_CONFIG_ALLOW_SYSTEM_LIBS turn the respective filter off, and PKG_CONFIG_SYSTEM_INCLUDE_PATH / PKG_CONFIG_SYSTEM_LIBRARY_PATH (colon-separated, mirroring PATH) replace the directory lists below.

Constant Summary collapse

DEFAULT_INCLUDE_DIRECTORIES =

What counts as a system directory when nothing overrides it.

["/usr/include"].freeze
MULTIARCH_LIBRARY_DIRECTORIES =

What counts as a system library directory, in two groups.

The multiarch pair is here because CI measured the real pkg-config against a Debian zlib.pc (libdir=$prefix/lib/x86_64-linux-gnu) and found it drops the -L for that directory too, not just plain /usr/lib: on Debian/Ubuntu the multiarch libdir is a system libdir as far as pkg-config is concerned. It is applied only when the directory exists, because a multiarch libdir is a Debian/Ubuntu layout: on a host without one (Alpine, measured in CI) the real pkg-config keeps a -L naming it, since there it is an ordinary directory rather than one the linker already searches. Dropping it there made this shim emit -lz where the real tool emitted -L/usr/lib/x86_64-linux-gnu -lz (docs/development/STEPS.md Step 196).

/usr/lib, /lib and /usr/lib64 are unconditional: they are system libdirs wherever they exist, and gating them on existence would change what this shim emits on the hosts the other measurements were taken on.

The lists are deliberately kept in step with the other hardcoded "default search directory" lists in this codebase -- Link::LibraryResolver::DEFAULT_SYSTEM_DIRS and SearchPath::DEFAULT_DIRECTORIES both already special-case the same multiarch path -- on the theory that a directory this shim's own linker searches by default is never worth emitting a -L for; that is the whole point of this filter.

/usr/local/lib is deliberately not included even though LibraryResolver::DEFAULT_SYSTEM_DIRS lists it: the real pkg-config does not treat it as a system directory, and adding it would make this shim diverge from the measured behaviour instead of matching it.

[
  "/usr/lib/x86_64-linux-gnu",
  "/lib/x86_64-linux-gnu"
].freeze
UNIVERSAL_LIBRARY_DIRECTORIES = 
[
  "/usr/lib",
  "/lib",
  "/usr/lib64"
].freeze

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(env = ENV) ⇒ SystemPathFilter

env is an argument (defaulting to the process environment) for the same reason SearchPath.directories takes one: it keeps the lookup injectable from a test without mutating the global ENV.



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# File 'lib/rubycc/pkgconf/system_path_filter.rb', line 71

def initialize(env = ENV)
  @include_directories = directory_list(env["PKG_CONFIG_SYSTEM_INCLUDE_PATH"], DEFAULT_INCLUDE_DIRECTORIES)
  @library_directories = directory_list(env["PKG_CONFIG_SYSTEM_LIBRARY_PATH"],
                                       self.class.default_library_directories)
  @keep_system_includes = set?(env["PKG_CONFIG_ALLOW_SYSTEM_CFLAGS"])
  @keep_system_libraries = set?(env["PKG_CONFIG_ALLOW_SYSTEM_LIBS"])
end

Class Method Details

.default_library_directories ⇒ Object

The system libdirs on this host, in the order above.



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# File 'lib/rubycc/pkgconf/system_path_filter.rb', line 64

def self.default_library_directories
  MULTIARCH_LIBRARY_DIRECTORIES.select { |d| File.directory?(d) } + UNIVERSAL_LIBRARY_DIRECTORIES
end

Instance Method Details

#cflags(tokens) ⇒ Object

tokens with the system -I<dir> entries removed. Every other token (-D..., a bare -I, -l..., ...) is passed through untouched.



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# File 'lib/rubycc/pkgconf/system_path_filter.rb', line 81

def cflags(tokens)
  return tokens if @keep_system_includes

  reject_system(tokens, "-I", @include_directories)
end

#libs(tokens) ⇒ Object

tokens with the system -L<dir> entries removed; -l and the rest are passed through untouched.



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# File 'lib/rubycc/pkgconf/system_path_filter.rb', line 89

def libs(tokens)
  return tokens if @keep_system_libraries

  reject_system(tokens, "-L", @library_directories)
end