Added the necessary comments for all the skips in the libc-test/build.rs

Author: gautam899

libc-test/build.rs

@@ -3334,7 +3334,8 @@ fn test_neutrino(target: &str) {
 }
 
 fn which_vxworks() -> Option<(u32, u32)> {
-    let version = env::var("WIND_RELEASE_ID").ok()?;
+    let version = env::var("WIND_RELEASE_ID").ok()?; // When in VxWorks setup, WIND_RELEASE_ID is
+                                                     // always set as the version of the release.
 
     let mut pieces = version.trim().split(['.']);
 
@@ -3430,8 +3431,12 @@ fn test_vxworks(target: &str) {
     cfg.skip_const(move |constant| match constant.ident() {
         // sighandler_t weirdness
         "SIG_DFL" | "SIG_ERR" | "SIG_IGN"
-        // This is not defined in vxWorks
-        | "RTLD_DEFAULT" | "S_ISVTX" | "SIGIO" | "SIGWINCH" | "SIGLOST" | "PRIO_PROCESS"  => true,
+        // These are not defined in VxWorks
+        | "RTLD_DEFAULT" | "PRIO_PROCESS"
+        // Sticky bits not supported
+        | "S_ISVTX"
+        // The following are obsolete for VxWorks
+        | "SIGIO" | "SIGWINCH" | "SIGLOST" => true,
         _ => false,
     });
     // FIXME(vxworks)
@@ -3444,7 +3449,9 @@ fn test_vxworks(target: &str) {
         move |struct_, field| match (struct_.ident(), field.ident()) {
             ("siginfo_t", "si_value")
             | ("stat", "st_size")
+            // sighandler_t type is super weird
             | ("sigaction", "sa_sigaction")
+            // sa_u_t type is not defined in vxworks
             | ("sigaction", "sa_u") => true,
             _ => false,
         },
@@ -3462,12 +3469,14 @@ fn test_vxworks(target: &str) {
     cfg.skip_fn(move |func| match func.ident() {
         // sighandler_t
         "signal"
+        // This is used a realpath and not _realpath
         | "_realpath"
         // not used in static linking by default
         | "dlerror" => true,
         _ => false,
     });
 
+    // Not defined in vxworks. Just a crate specific union type.
     cfg.skip_union(move |u| u.ident() == "sa_u_t");
 
     ctest::generate_test(&mut cfg, "../src/lib.rs", "ctest_output.rs").unwrap();