macro: introduce new TAKE_FD() macro

This is similar to TAKE_PTR() but operates on file descriptors, and thus
assigns -1 to the fd parameter after returning it.

Removes 60 lines from our codebase. Pretty good too I think.

src/basic/fd-util.c

@@ -484,10 +484,7 @@ int acquire_data_fd(const void *data, size_t size, unsigned flags) {
                 if (r < 0)
                         return r;
 
-                r = fd;
-                fd = -1;
-
-                return r;
+                return TAKE_FD(fd);
         }
 
 try_pipe:
@@ -524,10 +521,7 @@ try_pipe:
 
                 (void) fd_nonblock(pipefds[0], false);
 
-                r = pipefds[0];
-                pipefds[0] = -1;
-
-                return r;
+                return TAKE_FD(pipefds[0]);
         }
 
 try_dev_shm:

src/basic/fd-util.h

@@ -105,3 +105,11 @@ int rearrange_stdio(int original_input_fd, int original_output_fd, int original_
 static inline int make_null_stdio(void) {
         return rearrange_stdio(-1, -1, -1);
 }
+
+/* Like TAKE_PTR() but for file descriptors, resetting them to -1 */
+#define TAKE_FD(fd)                             \
+        ({                                      \
+                int _fd_ = (fd);                \
+                (fd) = -1;                      \
+                _fd_;                           \
+        })

src/basic/fs-util.c

@@ -730,8 +730,7 @@ int chase_symlinks(const char *path, const char *original_root, unsigned flags,
                         }
 
                         safe_close(fd);
-                        fd = fd_parent;
-                        fd_parent = -1;
+                        fd = TAKE_FD(fd_parent);
 
                         continue;
                 }
@@ -849,8 +848,7 @@ int chase_symlinks(const char *path, const char *original_root, unsigned flags,
 
                 /* And iterate again, but go one directory further down. */
                 safe_close(fd);
-                fd = child;
-                child = -1;
+                fd = TAKE_FD(child);
         }
 
         if (!done) {
@@ -864,16 +862,11 @@ int chase_symlinks(const char *path, const char *original_root, unsigned flags,
                 *ret = TAKE_PTR(done);
 
         if (flags & CHASE_OPEN) {
-                int q;
-
                 /* Return the O_PATH fd we currently are looking to the caller. It can translate it to a proper fd by
                  * opening /proc/self/fd/xyz. */
 
                 assert(fd >= 0);
-                q = fd;
-                fd = -1;
-
-                return q;
+                return TAKE_FD(fd);
         }
 
         return exists;

src/basic/memfd-util.c

@@ -168,8 +168,5 @@ int memfd_new_and_map(const char *name, size_t sz, void **p) {
         if (r < 0)
                 return r;
 
-        r = fd;
-        fd = -1;
-
-        return r;
+        return TAKE_FD(fd);
 }

src/basic/terminal-util.c

@@ -496,10 +496,7 @@ int acquire_terminal(
                 fd = safe_close(fd);
         }
 
-        r = fd;
-        fd = -1;
-
-        return r;
+        return TAKE_FD(fd);
 }
 
 int release_terminal(void) {