Merge pull request #15573 from motiejus/resolv_dn

glibc hacks: also add a few dn_* functions

lib/libc/glibc/README.md

@@ -6,3 +6,4 @@ need to be cherry-picked in the future glibc header upgrades:
 
 - 39083c31a550ed80f369f60d35791e98904b8096
 - a89813ef282c092a9caf699731c7faaf485acabe
+- 3eaca9bbc6fee4b6be0f22b844f7d3214222f434

lib/libc/include/generic-glibc/resolv.h

@@ -170,16 +170,20 @@ __END_DECLS
 #define res_isourserver		__res_isourserver
 
 /* In glibc 2.33 and earlier res_search, res_nsearch, res_query, res_nquery,
- * res_querydomain, res_nquerydomain were #define'd to __res_search,
- * __res_nsearch, etc. glibc 2.34 onwards removes the macros and exposes the
- * symbols directly. New glibc exposes compat symbols with underscores for
- * backwards compatibility. Applications linked to glibc 2.34+ are expected
- * to use the non-underscored symbols.
+ * res_querydomain, res_nquerydomain, dn_skipname, dn_comp, dn_expand were
+ * #define'd to __res_search, __res_nsearch, etc. glibc 2.34 onwards removes
+ * the macros and exposes the symbols directly. New glibc exposes compat
+ * symbols with underscores for backwards compatibility. Applications linked to
+ * glibc 2.34+ are expected to use the non-underscored symbols.
  *
- * It will be enough to bring the macros back when compiling against the older
- * glibc versions.
+ * It is enough to bring the macros back when compiling against the older glibc
+ * versions.
  *
- * See glibc commit ea9878ec271c791880fcbbe519d70c42f8113750.
+ * See glibc commits:
+ * - ea9878ec271c791880fcbbe519d70c42f8113750 res_*
+ * - 391e02236b931132c0e8b5ba4c3b087c2aaa1044 dn_skipname
+ * - fd8a87c0c1932de591e7ad108ff6288a4b6b18c9 dn_comp
+ * - 640bbdf71c6f10ac26252ac67a22902e26657bd8 dn_expand
  */
 #if (__GLIBC__ == 2 && __GLIBC_MINOR__ < 34)
 #define res_search        __res_search
@@ -188,6 +192,9 @@ __END_DECLS
 #define res_nquery        __res_nquery
 #define res_querydomain   __res_querydomain
 #define res_nquerydomain  __res_nquerydomain
+#define dn_skipname       __dn_skipname
+#define dn_comp           __dn_comp
+#define dn_expand         __dn_expand
 #endif
 /* end glibc compat hacks */
 
@@ -327,4 +334,4 @@ void		res_nclose (res_state) __THROW;
 
 __END_DECLS
 
-#endif /* !_RESOLV_H_ */
+#endif /* !_RESOLV_H_ */

test/link/glibc_compat/main.c

@@ -34,4 +34,7 @@ int main() {
     printf("address to res_nquery: %p\n", res_nquery);
     printf("address to res_querydomain: %p\n", res_querydomain);
     printf("address to res_nquerydomain: %p\n", res_nquerydomain);
+    printf("address to dn_skipname: %p\n", dn_skipname);
+    printf("address to dn_comp: %p\n", dn_comp);
+    printf("address to dn_expand: %p\n", dn_expand);
 }