adopt the get[pw/gr]ent_r def used by FreeBSD

src/unix/solarish/compat.rs

@@ -1,7 +1,6 @@
 // Common functions that are unfortunately missing on illumos and
 // Solaris, but often needed by other crates.
 
-use core::convert::TryInto;
 use unix::solarish::*;
 
 const PTEM: &[u8] = b"ptem\0";
@@ -177,13 +176,18 @@ pub unsafe fn getpwent_r(
     buflen: ::size_t,
     result: *mut *mut passwd,
 ) -> ::c_int {
-    let res = native_getpwent_r(pwd, buf, buflen.try_into().unwrap());
-    if res.is_null() {
-        -1
+    let old_errno = *::___errno();
+    *::___errno() = 0;
+    *result = native_getpwent_r(pwd, buf, buflen.min(::c_int::MAX as ::size_t) as ::c_int);
+
+    let ret = if (*result).is_null() {
+        *::___errno()
     } else {
-        *result = res;
         0
-    }
+    };
+    *::___errno() = old_errno;
+
+    ret
 }
 
 pub unsafe fn getgrent_r(
@@ -192,11 +196,16 @@ pub unsafe fn getgrent_r(
     buflen: ::size_t,
     result: *mut *mut ::group,
 ) -> ::c_int {
-    let res = native_getgrent_r(grp, buf, buflen.try_into().unwrap());
-    if res.is_null() {
-        -1
+    let old_errno = *::___errno();
+    *::___errno() = 0;
+    *result = native_getgrent_r(grp, buf, buflen.min(::c_int::MAX as ::size_t) as ::c_int);
+
+    let ret = if (*result).is_null() {
+        *::___errno()
     } else {
-        *result = res;
         0
-    }
+    };
+    *::___errno() = old_errno;
+
+    ret
 }