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, 5 deletions

diff --git a/libgcompat/math.c b/libgcompat/math.c
index 42ed032..2982116 100644
--- a/libgcompat/math.c
+++ b/libgcompat/math.c
@@ -1,26 +1,27 @@
 #include <math.h> /* isinf, isnan */
 
+#include "alias.h" /* weak_alias */
+
 int __isinff(float number)
 {
 	return isinf(number);
 }
+weak_alias(__isinff, isinff);
 
 int __isinf(double number)
 {
 	return isinf(number);
 }
+weak_alias(__isinf, isinf);
 
 int __isnanf(float number)
 {
 	return isnan(number);
 }
+weak_alias(__isnanf, isnanf);
 
 int __isnan(double number)
 {
 	return isnan(number);
 }
-
-extern __typeof(__isnanf) isnanf __attribute__((weak, alias("__isnanf")));
-extern __typeof(__isnan) isnan __attribute__((weak, alias("__isnan")));
-extern __typeof(__isinff) isinff __attribute__((weak, alias("__isinff")));
-extern __typeof(__isinf) isinf __attribute__((weak, alias("__isinf")));
+weak_alias(__isnan, isnan);