libgcompat: Add and use a macro for defining symbol aliases

* Prefer providing the underscore-prefixed symbol as the strong
  definition.
* Do not use a weak alias if the alias is also underscore-prefixed.
* Make libgcompat objects depend on the new header.

[NOTE: I originally took the weak_alias macro from musl's libc.h, but
       it's trivial and the same pattern already in use. If desired, I
       can add the musl copyright notice.]

Signed-off-by: Samuel Holland <samuel@sholland.org>

1 files changed, 6 insertions, 7 deletions

diff --git a/libgcompat/resolv.c b/libgcompat/resolv.c
index 3566dcd..7ad984f 100644
--- a/libgcompat/resolv.c
+++ b/libgcompat/resolv.c
@@ -9,7 +9,9 @@
 #include <resolv.h> /* res_state */
 #include <string.h> /* memcpy, memset */
 
-static inline int res_ninit(res_state statp)
+#include "alias.h" /* weak_alias */
+
+static inline int __res_ninit(res_state statp)
 {
 	int rc = res_init();
 	if (statp != &_res) {
@@ -17,8 +19,9 @@ static inline int res_ninit(res_state statp)
 	}
 	return rc;
 }
+weak_alias(__res_ninit, res_ninit);
 
-static inline int res_nclose(res_state statp)
+static inline int __res_nclose(res_state statp)
 {
 	if (!statp) {
 		return -1;
@@ -28,8 +31,4 @@ static inline int res_nclose(res_state statp)
 	}
 	return 0;
 }
-
-extern __typeof(res_ninit) __res_ninit
-    __attribute__((weak, alias("res_ninit")));
-extern __typeof(res_nclose) __res_nclose
-    __attribute__((weak, alias("res_nclose")));
+weak_alias(__res_nclose, res_nclose);