refactor build script to use a function to set cfgs

Author: pietroalbini

build.rs

@@ -25,94 +25,92 @@ fn main() {
     // On CI, we detect the actual FreeBSD version and match its ABI exactly,
     // running tests to ensure that the ABI is correct.
     match which_freebsd() {
-        Some(10) if libc_ci || rustc_dep_of_std => {
-            println!("cargo:rustc-cfg=freebsd10")
-        }
-        Some(11) if libc_ci => println!("cargo:rustc-cfg=freebsd11"),
-        Some(12) if libc_ci => println!("cargo:rustc-cfg=freebsd12"),
-        Some(13) if libc_ci => println!("cargo:rustc-cfg=freebsd13"),
-        Some(14) if libc_ci => println!("cargo:rustc-cfg=freebsd14"),
-        Some(_) | None => println!("cargo:rustc-cfg=freebsd11"),
+        Some(10) if libc_ci || rustc_dep_of_std => set_cfg("freebsd10"),
+        Some(11) if libc_ci => set_cfg("freebsd11"),
+        Some(12) if libc_ci => set_cfg("freebsd12"),
+        Some(13) if libc_ci => set_cfg("freebsd13"),
+        Some(14) if libc_ci => set_cfg("freebsd14"),
+        Some(_) | None => set_cfg("freebsd11"),
     }
 
     // On CI: deny all warnings
     if libc_ci {
-        println!("cargo:rustc-cfg=libc_deny_warnings");
+        set_cfg("libc_deny_warnings");
     }
 
     // Rust >= 1.15 supports private module use:
     if rustc_minor_ver >= 15 || rustc_dep_of_std {
-        println!("cargo:rustc-cfg=libc_priv_mod_use");
+        set_cfg("libc_priv_mod_use");
     }
 
     // Rust >= 1.19 supports unions:
     if rustc_minor_ver >= 19 || rustc_dep_of_std {
-        println!("cargo:rustc-cfg=libc_union");
+        set_cfg("libc_union");
     }
 
     // Rust >= 1.24 supports const mem::size_of:
     if rustc_minor_ver >= 24 || rustc_dep_of_std {
-        println!("cargo:rustc-cfg=libc_const_size_of");
+        set_cfg("libc_const_size_of");
     }
 
     // Rust >= 1.25 supports repr(align):
     if rustc_minor_ver >= 25 || rustc_dep_of_std || align_cargo_feature {
-        println!("cargo:rustc-cfg=libc_align");
+        set_cfg("libc_align");
     }
 
     // Rust >= 1.26 supports i128 and u128:
     if rustc_minor_ver >= 26 || rustc_dep_of_std {
-        println!("cargo:rustc-cfg=libc_int128");
+        set_cfg("libc_int128");
     }
 
     // Rust >= 1.30 supports `core::ffi::c_void`, so libc can just re-export it.
     // Otherwise, it defines an incompatible type to retaining
     // backwards-compatibility.
     if rustc_minor_ver >= 30 || rustc_dep_of_std {
-        println!("cargo:rustc-cfg=libc_core_cvoid");
+        set_cfg("libc_core_cvoid");
     }
 
     // Rust >= 1.33 supports repr(packed(N)) and cfg(target_vendor).
     if rustc_minor_ver >= 33 || rustc_dep_of_std {
-        println!("cargo:rustc-cfg=libc_packedN");
-        println!("cargo:rustc-cfg=libc_cfg_target_vendor");
+        set_cfg("libc_packedN");
+        set_cfg("libc_cfg_target_vendor");
     }
 
     // Rust >= 1.40 supports #[non_exhaustive].
     if rustc_minor_ver >= 40 || rustc_dep_of_std {
-        println!("cargo:rustc-cfg=libc_non_exhaustive");
+        set_cfg("libc_non_exhaustive");
     }
 
     // Rust >= 1.47 supports long array:
     if rustc_minor_ver >= 47 || rustc_dep_of_std {
-        println!("cargo:rustc-cfg=libc_long_array");
+        set_cfg("libc_long_array");
     }
 
     if rustc_minor_ver >= 51 || rustc_dep_of_std {
-        println!("cargo:rustc-cfg=libc_ptr_addr_of");
+        set_cfg("libc_ptr_addr_of");
     }
 
     // Rust >= 1.37.0 allows underscores as anonymous constant names.
     if rustc_minor_ver >= 37 || rustc_dep_of_std {
-        println!("cargo:rustc-cfg=libc_underscore_const_names");
+        set_cfg("libc_underscore_const_names");
     }
 
     // #[thread_local] is currently unstable
     if rustc_dep_of_std {
-        println!("cargo:rustc-cfg=libc_thread_local");
+        set_cfg("libc_thread_local");
     }
 
     // Rust >= 1.62.0 allows to use `const_extern_fn` for "Rust" and "C".
     if rustc_minor_ver >= 62 {
-        println!("cargo:rustc-cfg=libc_const_extern_fn");
+        set_cfg("libc_const_extern_fn");
     } else {
         // Rust < 1.62.0 requires a crate feature and feature gate.
         if const_extern_fn_cargo_feature {
             if !is_nightly || rustc_minor_ver < 40 {
                 panic!("const-extern-fn requires a nightly compiler >= 1.40");
             }
-            println!("cargo:rustc-cfg=libc_const_extern_fn_unstable");
-            println!("cargo:rustc-cfg=libc_const_extern_fn");
+            set_cfg("libc_const_extern_fn_unstable");
+            set_cfg("libc_const_extern_fn");
         }
     }
 }
@@ -181,3 +179,7 @@ fn which_freebsd() -> Option<i32> {
         _ => None,
     }
 }
+
+fn set_cfg(cfg: &str) {
+    println!("cargo:rustc-cfg={}", cfg);
+}