adjust types in FILE struct to make line buffering check less expensive

the choice of signed char for lbf was a theoretically space-saving
hack that was not helping, and was unwantedly expensive. while
comparing bytes against a byte-sized member sounds easy, the trick
here was that the byte to be compared was unsigned while the lbf
member was signed, making it possible to set lbf negative to disable
line buffering. however, this imposed a requirement to promote both
operands, zero-extending one and sign-extending the other, in order to
compare them.

to fix this, repurpose the waiters count slot (unused since commit
c21f750727515602a9e84f2a190ee8a0a2aeb2a1). while we're at it, switch
mode (orientation) from signed char to int as well. this makes no
semantic difference (its only possible values are -1, 0, and 1) but it
might help on archs where byte access is awkward.

diff --git a/src/internal/stdio_impl.h b/src/internal/stdio_impl.h
index 055ef718f94a0f0d8819c4f28fa503edbaabf503..d7398f5913bed58de2c97c884aa262ab6514c121 100644 (file)
--- a/src/internal/stdio_impl.h
+++ b/src/internal/stdio_impl.h
@@ -34,11 +34,9 @@ struct _IO_FILE {
        int fd;
        int pipe_pid;
        long lockcount;
-       short dummy3;
-       signed char mode;
-       signed char lbf;
+       int mode;
        volatile int lock;
-       volatile int waiters;
+       int lbf;
        void *cookie;
        off_t off;
        char *getln_buf;