build: fix missing function prototype on older gcc

vtjnash · KristofferC · commit 6b89ea656cfa · 2020-02-17T15:35:56.000+01:00
The ffs function is not always available under that name, use instead the compiler name for it which may always be used. (cherry picked from commit ef17985)
diff --git a/src/gc.h b/src/gc.h
@@ -374,7 +374,7 @@ STATIC_INLINE unsigned ffs_u32(uint32_t bitvec)
     _BitScanForward(&j, bitvec);
     return j;
 #else
-    return ffs(bitvec) - 1;
+    return __builtin_ffs(bitvec) - 1;
 #endif
 }
 #endif

Original file line number	Diff line number	Diff line change
`@@ -374,7 +374,7 @@ STATIC_INLINE unsigned ffs_u32(uint32_t bitvec)`
`374`	`374`	`_BitScanForward(&j, bitvec);`
`375`	`375`	`return j;`
`376`	`376`	`#else`
`377`		`- return ffs(bitvec) - 1;`
	`377`	`+ return __builtin_ffs(bitvec) - 1;`
`378`	`378`	`#endif`
`379`	`379`	`}`
`380`	`380`	`#endif`