unix: work around arm-linux-gnueabihf-gcc bug (#4537)

bnoordhuis · web-flow · commit 32603fd5ff56 · 2024-09-19T19:53:19.000+02:00
Both gcc 11 and 12 emit wrong code for a function call pointer in one very specific context. Fixes: #4532
diff --git a/src/unix/fs.c b/src/unix/fs.c
@@ -482,7 +482,10 @@ static ssize_t uv__preadv_or_pwritev(int fd,
     atomic_store_explicit(cache, (uintptr_t) p, memory_order_relaxed);
   }
 
-  f = p;
+  /* Use memcpy instead of `f = p` to work around a compiler bug,
+   * see https://github.com/libuv/libuv/issues/4532
+   */
+  memcpy(&f, &p, sizeof(p));
   return f(fd, bufs, nbufs, off);
 }
 

Original file line number	Diff line number	Diff line change
`@@ -482,7 +482,10 @@ static ssize_t uv__preadv_or_pwritev(int fd,`
`482`	`482`	`atomic_store_explicit(cache, (uintptr_t) p, memory_order_relaxed);`
`483`	`483`	`}`
`484`	`484`
`485`		`- f = p;`
	`485`	+ /* Use memcpy instead of `f = p` to work around a compiler bug,
	`486`	`+ * see https://github.com/libuv/libuv/issues/4532`
	`487`	`+ */`
	`488`	`+ memcpy(&f, &p, sizeof(p));`
`486`	`489`	`return f(fd, bufs, nbufs, off);`
`487`	`490`	`}`
`488`	`491`