greatly improve freopen behavior

1. don't open /dev/null just as a basis to copy flags; use shared
__fmodeflags function to get the right file flags for the mode.

2. handle the case (probably invalid, but whatever) case where the
original stream's file descriptor was closed; previously, the logic
re-closed it.

3. accept the "e" mode flag for close-on-exec; update dup3 to fallback
to using dup2 so we can simply call __dup3 instead of putting fallback
logic in freopen itself.

1 files changed, 1 insertions, 8 deletions

diff --git a/src/stdio/fopen.c b/src/stdio/fopen.c
index 03c10cd1..c741aede 100644
--- a/src/stdio/fopen.c
+++ b/src/stdio/fopen.c
@@ -13,14 +13,7 @@ FILE *fopen(const char *restrict filename, const char *restrict mode)
 	}
 
 	/* Compute the flags to pass to open() */
-	if (strchr(mode, '+')) flags = O_RDWR;
-	else if (*mode == 'r') flags = O_RDONLY;
-	else flags = O_WRONLY;
-	if (strchr(mode, 'x')) flags |= O_EXCL;
-	if (strchr(mode, 'e')) flags |= O_CLOEXEC;
-	if (*mode != 'r') flags |= O_CREAT;
-	if (*mode == 'w') flags |= O_TRUNC;
-	if (*mode == 'a') flags |= O_APPEND;
+	flags = __fmodeflags(mode);
 
 	fd = syscall_cp(SYS_open, filename, flags|O_LARGEFILE, 0666);
 	if (fd < 0) return 0;