On Tue, 2020-01-14 at 08:22 +0000, Baptiste Daroussin wrote:
> Author: bapt
> Date: Tue Jan 14 08:22:28 2020
> New Revision: 356725
> URL: https://svnweb.freebsd.org/changeset/base/356725
>
> Log:
> When system calls indicate an error they return -1, not some
> arbitrary
> value < 0. errno is only updated in this case.
>
What's the point of these changes, other than almost certainly leading
to worse code generation?
In most instruction sets, you can test for a value < 0 without using
any instructions, you only need to examine the condition flags after
loading the value. To compare equal to -1 typically requires at least
1 extra instruction, and on risc architectures typically at least two
extra (load -1 to a register then compare).
-- Ian
> Obtained from: OpenBSD
> MFC after: 3 days
>
> Modified:
> head/usr.bin/diff/diff.c
> head/usr.bin/diff/diffreg.c
>
> Modified: head/usr.bin/diff/diff.c
> =====================================================================
> =========
> --- head/usr.bin/diff/diff.c Tue Jan 14 08:18:04 2020 (r356724)
> +++ head/usr.bin/diff/diff.c Tue Jan 14 08:22:28 2020 (r356725)
> @@ -1,4 +1,4 @@
> -/* $OpenBSD: diff.c,v 1.65 2015/12/29 19:04:46 gsoares Exp $ */
> +/* $OpenBSD: diff.c,v 1.67 2019/06/28 13:35:00 deraadt Exp $ */
>
> /*
> * Copyright (c) 2003 Todd C. Miller <todd.mil...@courtesan.com>
> @@ -316,12 +316,12 @@ main(int argc, char **argv)
> } else {
> if (S_ISDIR(stb1.st_mode)) {
> argv[0] = splice(argv[0], argv[1]);
> - if (stat(argv[0], &stb1) < 0)
> + if (stat(argv[0], &stb1) == -1)
> err(2, "%s", argv[0]);
> }
> if (S_ISDIR(stb2.st_mode)) {
> argv[1] = splice(argv[1], argv[0]);
> - if (stat(argv[1], &stb2) < 0)
> + if (stat(argv[1], &stb2) == -1)
> err(2, "%s", argv[1]);
> }
> print_status(diffreg(argv[0], argv[1], dflags, 1),
> argv[0],
>
> Modified: head/usr.bin/diff/diffreg.c
> =====================================================================
> =========
> --- head/usr.bin/diff/diffreg.c Tue Jan 14 08:18:04 2020 (r356
> 724)
> +++ head/usr.bin/diff/diffreg.c Tue Jan 14 08:22:28 2020 (r356
> 725)
> @@ -1,4 +1,4 @@
> -/* $OpenBSD: diffreg.c,v 1.92 2019/06/28 05:35:34 deraadt Exp $
> */
> +/* $OpenBSD: diffreg.c,v 1.93 2019/06/28 13:35:00 deraadt Exp $
> */
>
> /*-
> * SPDX-License-Identifier: BSD-4-Clause
> @@ -277,7 +277,7 @@ diffreg(char *file1, char *file2, int flags, int
> capsi
> else {
> if (!S_ISREG(stb1.st_mode)) {
> if ((f1 = opentemp(file1)) == NULL ||
> - fstat(fileno(f1), &stb1) < 0) {
> + fstat(fileno(f1), &stb1) == -1) {
> warn("%s", file1);
> status |= 2;
> goto closem;
> @@ -298,7 +298,7 @@ diffreg(char *file1, char *file2, int flags, int
> capsi
> else {
> if (!S_ISREG(stb2.st_mode)) {
> if ((f2 = opentemp(file2)) == NULL ||
> - fstat(fileno(f2), &stb2) < 0) {
> + fstat(fileno(f2), &stb2) == -1) {
> warn("%s", file2);
> status |= 2;
> goto closem;
> @@ -446,7 +446,7 @@ opentemp(const char *f)
>
> if (strcmp(f, "-") == 0)
> ifd = STDIN_FILENO;
> - else if ((ifd = open(f, O_RDONLY, 0644)) < 0)
> + else if ((ifd = open(f, O_RDONLY, 0644)) == -1)
> return (NULL);
>
> (void)strlcpy(tempfile, _PATH_TMP "/diff.XXXXXXXX",
> sizeof(tempfile));
> @@ -942,7 +942,7 @@ preadline(int fd, size_t rlen, off_t off)
> ssize_t nr;
>
> line = xmalloc(rlen + 1);
> - if ((nr = pread(fd, line, rlen, off)) < 0)
> + if ((nr = pread(fd, line, rlen, off)) == -1)
> err(2, "preadline");
> if (nr > 0 && line[nr-1] == '\n')
> nr--;
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