lib: introduce i_close_fd_path()

It is like i_close_fd() but takes an argument with the name of the file
that's being closed.  The name is only used when printing the error
message due to a failed close() syscall.

src/lib/lib.c

@@ -29,8 +29,8 @@ struct atexit_callback {
 
 static ARRAY(struct atexit_callback) atexit_callbacks = ARRAY_INIT;
 
-void i_close_fd_real(int *fd, const char *arg, const char *func,
-		     const char *file, int line)
+void i_close_fd_path_real(int *fd, const char *path, const char *arg,
+			  const char *func, const char *file, int line)
 {
 	int saved_errno;
 
@@ -41,8 +41,11 @@ void i_close_fd_real(int *fd, const char *arg, const char *func,
 
 	saved_errno = errno;
 	if (unlikely(close(*fd) < 0))
-		i_error("%s: close(%s) @ %s:%d failed (fd=%d): %m",
-			func, arg, file, line, *fd);
+		i_error("%s: close(%s%s%s) @ %s:%d failed (fd=%d): %m",
+			func, arg,
+			(path == NULL) ? "" : " = ",
+			(path == NULL) ? "" : path,
+			file, line, *fd);
 	errno = saved_errno;
 
 	*fd = -1;

src/lib/macros.h

@@ -212,8 +212,10 @@
 /* Close the fd and set it to -1. This assert-crashes if fd == 0, and is a
    no-op if fd == -1. Normally fd == 0 would happen only if an uninitialized
    fd is attempted to be closed, which is a bug. */
-void i_close_fd_real(int *fd, const char *arg, const char *func, const char *file, int line);
-#define i_close_fd(fd) i_close_fd_real((fd), #fd, __func__, __FILE__, __LINE__)
+void i_close_fd_path_real(int *fd, const char *path, const char *arg,
+			  const char *func, const char *file, int line);
+#define i_close_fd(fd) i_close_fd_path_real((fd), NULL, #fd, __func__, __FILE__, __LINE__)
+#define i_close_fd_path(fd, path) i_close_fd_path_real((fd), (path), #fd, __func__, __FILE__, __LINE__)
 
 #ifndef STATIC_CHECKER
 #  define i_unreached() \