Fix fdopen mode-compatibility test and errno setting.

diff --git a/libc/stdio/stdio.c b/libc/stdio/stdio.c
index 73b9d1a..fe1c6a0 100644 (file)
--- a/libc/stdio/stdio.c
+++ b/libc/stdio/stdio.c
@@ -701,8 +701,15 @@ const char *mode;
        if (fname) {                            /* Open the file itself */
                fd = open(fname, open_mode, 0666);
        } else {                                        /* fdopen -- check mode is compatible. */
+#if O_ACCMODE != 3 || O_RDONLY != 0 || O_WRONLY != 1 || O_RDWR != 2
+#error Assumption violated - mode constants
+#endif
                cur_mode = fcntl(fd, F_GETFL);
-               if ((cur_mode == -1) || ((cur_mode ^ open_mode) & O_ACCMODE)) {
+               if (cur_mode == -1) {
+                       fd = -1;
+               } else if (!(cur_mode & O_RDWR) 
+                                  && ((cur_mode ^ open_mode) & O_ACCMODE)) {
+                       errno = EINVAL;
                        fd = -1;
                }
        }