Tracking how *-sys crates use pkg-config and vcpkg

[weihanglo]

This is an issue tracking usages of pkg-config and vcpkg in common *-sys crates.

By having a better understanding of how they are used, we could come up with a common declarative interface covering most use cases.

[weihanglo]

curl-sys

pkg-config

• Calls when probing
  • pkg_config::Config::cargo_metadata(true)
• Prints one cargo:include={path} instruction per include paths.
• Risks
  • Has a cargo feature force-system-lib-on-osx that forces using system library.
  • Additional logic checking http2 cargo feature for different run of pkg-conig probe

vcpkg

• Calls when probing
  • vcpkg::Config::emit_includes(true)
  • vcpkg::Config::lib_names("libcurl_imp", "libcurl") for different lib/ddl names.
• Prints one cargo:include={path} instruction per include paths.
• Risks
  • Probes twice if the first call found nothing
  • Probes no only curl but also other libs, such as openssl, libssh2 and zlib.
  • Has some custom cargo:rustc-link-lib instructions for crypt32, gdi32, and user32.

[weihanglo]

libgit2-sys

pkg-config

• Calls:
  • pkg_config::Config::range_version("1.7.2".."1.8.0")
• Prints one cargo:root={path} instruction per include paths.
• Risks: None

vcpkg

None.

[weihanglo]

openssl-sys

pkg-config

• Calls:
  • set PKG_CONFIG_ALLOW_CROSS=1
  • pkg_config::Config::print_system_libs(false)
• Prints one cargo:include={path} instruction per include paths.
• Risks:
  • set PKG_CONFIG_ALLOW_CROSS=1 based on platforms.
  • Hard-coded some well-known locations before probing.
  • Retry with vcpkg when failed.

vcpkg

• Calls:
  • vcpkg::Config::emit_includes(true)
• Risks:
  • Has some custom cargo:rustc-link-lib instructions for crypt32, gdi32, and user32.
  • Hard-coded some well-known locations before probing.
  • Is a fallback when pkg-config failed.

[weihanglo]

libssh2-sys

pkg-config

• Calls: nothing special
• Prints one cargo:include={path} instruction per include paths.
• Risks:
  • Only when not in zlib-ng-compat mode will it probes.

vcpkg

• Calls:
  • vcpkg::Config::emit_includes(true)
• Prints one cargo:include={path} instruction per include paths.
• Risks:
  • Only when not in zlib-ng-compat mode will it probes.
  • Probes no only libssh2 but also other libs, such as openssl and zlib.
  • Has some custom cargo:rustc-link-lib instructions for crypt32, gdi32, and user32.

[weihanglo]

zstd-sys

pkg-config

• Calls:
  • pkg_config::Config::statik(true)
  • pkg_config::Config::cargo_metadata(!cfg!(feature = "non-cargo"))
• Prints cargo:include={} with ;-joined include paths
• Risks: None

vcpkg

None

[weihanglo]

lzma-sys

pkg-config

• Calls: nothing special
• Prints nothing. Only when vendoring will it print cargo:include={} with a local path.
• Risks:
  • There is a note that on MSVC if we use pkg-config, it may accidentally pick up lib from MingW, which is not desired.

vcpkg

None

[weihanglo]

libz-sys

pkg-config

• Calls:
  • pkg_config::Config::cargo_metadata(true)
  • pkg_config::Config::print_system_libs(false)
• Prints cargo:include={} with comma-joined include paths
• Risks:
  • Compile a smoke test c file to check if system zlib is linkable.
  • FreeBDS and Dragonfly are opted-out

vcpkg

• Calls:
  • vcpkg::Config::emit_includes(true)
• Risks:
  • For target.contains("windows"). Doesn't tell the different between gnu and msvc.