Try harder to define FFS correctly.

augustss · Oct 6, 2024 · 2d84d9d · 2d84d9d
1 parent def8252
commit 2d84d9d
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Showing 2 changed files with 14 additions and 1 deletion.
diff --git a/src/runtime/config-unix-32.h b/src/runtime/config-unix-32.h
@@ -4,4 +4,7 @@
 //#define WORD_SIZE 32
 
 #undef FFS
+#if _POSIX_VERSION >= 200112L
 #define FFS ffs
+#endif
+
diff --git a/src/runtime/config-unix-64.h b/src/runtime/config-unix-64.h
@@ -45,11 +45,21 @@
 
 /*
  * Find First Set
- * This macro must be defined.
+ * This macro should be defined.
  * It returns the number of the least significant bit that is set.
  * Numberings starts from 1.  If no bit is set, it should return 0.
  */
+#if defined(__gnu_linux__) || defined(__APPLE__) || defined(__FreeBSD__)
+/* Only some platforms have 64 bit ffsl function directly. */
 #define FFS ffsl
+#elif defined(__GNUC__)
+/* GCC has ffsl as a builtin. */
+#define FFS __builtin_ffsl
+/* CLANG has ffsl as a builtin. */
+#elif defined(__clang__) && __has_builtin(__builtin__ffsl)
+#define FFS __builtin_ffsl
+#endif
+
 
 /*
  * This is the character used for comma-separation in printf.