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comparison libpam-sys/src/pam_impl.rs @ 134:6c1e1bdb4164

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Use standard #[cfg] directives rather than custom proc macros. Instead of having to do a bunch of custom parsing and other logic that tools often choke on, this change introduces an easy way to depend upon custom #[cfg]s provided by the libpam-sys crate.
author Paul Fisher <paul@pfish.zone>
date Thu, 03 Jul 2025 11:03:36 -0400
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133:32b2a545ca3e 134:6c1e1bdb4164
1 /// An enum that knows its own values.
2 macro_rules! self_aware_enum {
3 (
4 $(#[$enumeta:meta])*
5 $viz:vis enum $name:ident {
6 $(
7 $(#[$itemeta:meta])*
8 $item:ident,
9 )*
10 }
11 ) => {
12 $(#[$enumeta])*
13 $viz enum $name {
14 $(
15 $(#[$itemeta])*
16 $item,
17 )*
18 }
19
20 // The implementations in this block are private for now
21 // to avoid putting a contract into the public API.
22 #[allow(dead_code)]
23 impl $name {
24 /// Iterator over the items in the enum. For internal use.
25 fn items() -> Vec<Self> {
26 vec![$(Self::$item),*]
27 }
28
29 /// Attempts to parse the enum from the string. For internal use.
30 fn try_from(value: &str) -> Result<Self, String> {
31 match value {
32 $(stringify!($item) => Ok(Self::$item),)*
33 _ => Err(value.into()),
34 }
35 }
36 }
37 };
38 }
39
40 self_aware_enum! {
41 /// The PAM implementations supported by `libpam-sys`.
42 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
43 #[cfg_attr(pam_impl, non_exhaustive)]
44 pub enum PamImpl {
45 /// [Linux-PAM] is provided by most Linux distributions.
46 ///
47 /// [Linux-PAM]: https://github.com/linux-pam/linux-pam
48 LinuxPam,
49 /// [OpenPAM] is used by most BSDs, including Mac OS X.
50 ///
51 /// [OpenPAM]: https://git.des.dev/OpenPAM/OpenPAM
52 OpenPam,
53 /// Illumos and Solaris use a derivative of [Sun's implementation][sun].
54 ///
55 /// [sun]: https://code.illumos.org/plugins/gitiles/illumos-gate/+/refs/heads/master/usr/src/lib/libpam
56 Sun,
57 /// Only the functionality and constants in [the PAM spec].
58 ///
59 /// [the PAM spec]: https://pubs.opengroup.org/onlinepubs/8329799/toc.htm
60 XSso,
61 }
62 }
63
64 #[cfg(pam_impl)]
65 include!(concat!(env!("OUT_DIR"), "/pam_impl_const.rs"));
66
67 /// Generates `cargo` directives for build scripts to enable `cfg(pam_impl)`.
68 ///
69 /// Print this in your `build.rs` script to be able to use the custom `pam_impl`
70 /// configuration directive.
71 ///
72 /// ```
73 /// // build.rs
74 /// use libpam_sys::pam_impl;
75 /// fn main() {
76 /// println!("{}", pam_impl::enable_pam_impl_cfg())
77 ///
78 /// // Whatever other stuff you do in your build.rs.
79 /// }
80 /// ```
81 ///
82 /// This will set the current `pam_impl` as well as registering all known
83 /// PAM implementations with `rustc-check-cfg` so you can easily use them:
84 ///
85 /// ```
86 /// #[cfg(pam_impl = "OpenPam")]
87 /// fn openpam_specific_func(handle: *const libpam_sys::pam_handle) {
88 /// let environ = libpam_sys::pam_getenvlist(handle);
89 /// // ...
90 /// libpam_sys::openpam_free_envlist()
91 /// }
92 ///
93 /// // This will give you a warning since "UnknownImpl" is not in the cfg.
94 /// #[cfg(not(pam_impl = "UnknownImpl"))]
95 /// fn do_something() {
96 /// // ...
97 /// }
98 /// ```
99 #[cfg(pam_impl)]
100 pub fn enable_pam_impl_cfg() -> String {
101 format!("{}\n{}", checkcfg(), implcfg(PamImpl::CURRENT_STR))
102 }
103
104 /// Generates the `cargo:rustc-check-cfg` directive to print in build scripts.
105 fn checkcfg() -> String {
106 let impls: Vec<_> = PamImpl::items()
107 .into_iter()
108 .map(|i| format!(r#""{i:?}""#))
109 .collect();
110 format!(
111 "\
112 cargo:rustc-check-cfg=cfg(pam_impl)\n\
113 cargo:rustc-check-cfg=cfg(pam_impl, values({impls}))\
114 ",
115 impls = impls.join(",")
116 )
117 }
118
119 fn implcfg(name: &str) -> String {
120 format!("cargo:rustc-cfg=pam_impl\ncargo:rustc-cfg=pam_impl={name:?}")
121 }