Bug Summary

File:src/usr.bin/tail/forward.c
Warning:line 111, column 10
Although the value stored to 'ch' is used in the enclosing expression, the value is never actually read from 'ch'

Annotated Source Code

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clang -cc1 -cc1 -triple amd64-unknown-openbsd7.0 -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name forward.c -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -mrelocation-model pic -pic-level 1 -pic-is-pie -mframe-pointer=all -relaxed-aliasing -fno-rounding-math -mconstructor-aliases -munwind-tables -target-cpu x86-64 -target-feature +retpoline-indirect-calls -target-feature +retpoline-indirect-branches -tune-cpu generic -debugger-tuning=gdb -fcoverage-compilation-dir=/usr/src/usr.bin/tail/obj -resource-dir /usr/local/lib/clang/13.0.0 -internal-isystem /usr/local/lib/clang/13.0.0/include -internal-externc-isystem /usr/include -O2 -fdebug-compilation-dir=/usr/src/usr.bin/tail/obj -ferror-limit 19 -fwrapv -D_RET_PROTECTOR -ret-protector -fgnuc-version=4.2.1 -vectorize-loops -vectorize-slp -fno-builtin-malloc -fno-builtin-calloc -fno-builtin-realloc -fno-builtin-valloc -fno-builtin-free -fno-builtin-strdup -fno-builtin-strndup -analyzer-output=html -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /home/ben/Projects/vmm/scan-build/2022-01-12-194120-40624-1 -x c /usr/src/usr.bin/tail/forward.c
1/* $OpenBSD: forward.c,v 1.33 2019/06/28 13:35:04 deraadt Exp $ */
2/* $NetBSD: forward.c,v 1.7 1996/02/13 16:49:10 ghudson Exp $ */
3
4/*-
5 * Copyright (c) 1991, 1993
6 * The Regents of the University of California. All rights reserved.
7 *
8 * This code is derived from software contributed to Berkeley by
9 * Edward Sze-Tyan Wang.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 * notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in the
18 * documentation and/or other materials provided with the distribution.
19 * 3. Neither the name of the University nor the names of its contributors
20 * may be used to endorse or promote products derived from this software
21 * without specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * SUCH DAMAGE.
34 */
35
36#include <sys/types.h>
37#include <sys/stat.h>
38#include <sys/event.h>
39
40#include <err.h>
41#include <errno(*__errno()).h>
42#include <stdio.h>
43#include <stdlib.h>
44#include <string.h>
45#include <unistd.h>
46
47#include "extern.h"
48
49static int rlines(struct tailfile *, off_t);
50static inline void tfprint(FILE *fp);
51static int tfqueue(struct tailfile *tf);
52static const struct timespec *tfreopen(struct tailfile *tf);
53
54static int kq = -1;
55
56/*
57 * forward -- display the file, from an offset, forward.
58 *
59 * There are eight separate cases for this -- regular and non-regular
60 * files, by bytes or lines and from the beginning or end of the file.
61 *
62 * FBYTES byte offset from the beginning of the file
63 * REG seek
64 * NOREG read, counting bytes
65 *
66 * FLINES line offset from the beginning of the file
67 * REG read, counting lines
68 * NOREG read, counting lines
69 *
70 * RBYTES byte offset from the end of the file
71 * REG seek
72 * NOREG cyclically read characters into a wrap-around buffer
73 *
74 * RLINES
75 * REG step back until the correct offset is reached.
76 * NOREG cyclically read lines into a wrap-around array of buffers
77 */
78void
79forward(struct tailfile *tf, int nfiles, enum STYLE style, off_t origoff)
80{
81 int ch;
82 struct tailfile *ctf, *ltf;
83 struct kevent ke;
84 const struct timespec *ts = NULL((void *)0);
85 int i;
86 int nevents;
87
88 if (nfiles < 1)
89 return;
90
91 if (fflag && (kq = kqueue()) == -1)
92 warn("kqueue");
93
94 for (i = 0; i < nfiles; i++) {
95 off_t off = origoff;
96 if (nfiles > 1)
97 printfname(tf[i].fname);
98
99 switch(style) {
100 case FBYTES:
101 if (off == 0)
102 break;
103 if (S_ISREG(tf[i].sb.st_mode)((tf[i].sb.st_mode & 0170000) == 0100000)) {
104 if (tf[i].sb.st_size < off)
105 off = tf[i].sb.st_size;
106 if (fseeko(tf[i].fp, off, SEEK_SET0) == -1) {
107 ierr(tf[i].fname);
108 return;
109 }
110 } else while (off--)
111 if ((ch = getc(tf[i].fp)(!__isthreaded ? (--(tf[i].fp)->_r < 0 ? __srget(tf[i].
fp) : (int)(*(tf[i].fp)->_p++)) : (getc)(tf[i].fp))) == EOF(-1)) {
Although the value stored to 'ch' is used in the enclosing expression, the value is never actually read from 'ch'
112 if (ferror(tf[i].fp)(!__isthreaded ? (((tf[i].fp)->_flags & 0x0040) != 0) :
(ferror)(tf[i].fp))) {
113 ierr(tf[i].fname);
114 return;
115 }
116 break;
117 }
118 break;
119 case FLINES:
120 if (off == 0)
121 break;
122 for (;;) {
123 if ((ch = getc(tf[i].fp)(!__isthreaded ? (--(tf[i].fp)->_r < 0 ? __srget(tf[i].
fp) : (int)(*(tf[i].fp)->_p++)) : (getc)(tf[i].fp))) == EOF(-1)) {
124 if (ferror(tf[i].fp)(!__isthreaded ? (((tf[i].fp)->_flags & 0x0040) != 0) :
(ferror)(tf[i].fp))) {
125 ierr(tf[i].fname);
126 return;
127 }
128 break;
129 }
130 if (ch == '\n' && !--off)
131 break;
132 }
133 break;
134 case RBYTES:
135 if (S_ISREG(tf[i].sb.st_mode)((tf[i].sb.st_mode & 0170000) == 0100000)) {
136 if (tf[i].sb.st_size >= off &&
137 fseeko(tf[i].fp, -off, SEEK_END2) == -1) {
138 ierr(tf[i].fname);
139 return;
140 }
141 } else if (off == 0) {
142 while (getc(tf[i].fp)(!__isthreaded ? (--(tf[i].fp)->_r < 0 ? __srget(tf[i].
fp) : (int)(*(tf[i].fp)->_p++)) : (getc)(tf[i].fp)) != EOF(-1))
143 ;
144 if (ferror(tf[i].fp)(!__isthreaded ? (((tf[i].fp)->_flags & 0x0040) != 0) :
(ferror)(tf[i].fp))) {
145 ierr(tf[i].fname);
146 return;
147 }
148 } else {
149 if (bytes(&(tf[i]), off))
150 return;
151 }
152 break;
153 case RLINES:
154 if (S_ISREG(tf[i].sb.st_mode)((tf[i].sb.st_mode & 0170000) == 0100000)) {
155 if (!off) {
156 if (fseeko(tf[i].fp, (off_t)0,
157 SEEK_END2) == -1) {
158 ierr(tf[i].fname);
159 return;
160 }
161 } else if (rlines(&(tf[i]), off) != 0)
162 lines(&(tf[i]), off);
163 } else if (off == 0) {
164 while (getc(tf[i].fp)(!__isthreaded ? (--(tf[i].fp)->_r < 0 ? __srget(tf[i].
fp) : (int)(*(tf[i].fp)->_p++)) : (getc)(tf[i].fp)) != EOF(-1))
165 ;
166 if (ferror(tf[i].fp)(!__isthreaded ? (((tf[i].fp)->_flags & 0x0040) != 0) :
(ferror)(tf[i].fp))) {
167 ierr(tf[i].fname);
168 return;
169 }
170 } else {
171 if (lines(&(tf[i]), off))
172 return;
173 }
174 break;
175 default:
176 err(1, "Unsupported style");
177 }
178
179 tfprint(tf[i].fp);
180 if (fflag && tfqueue(&(tf[i])) == -1)
181 warn("Unable to follow %s", tf[i].fname);
182
183 }
184 ltf = &(tf[i-1]);
185
186 (void)fflush(stdout(&__sF[1]));
187 if (!fflag || kq == -1)
188 return;
189
190 while (1) {
191 if ((nevents = kevent(kq, NULL((void *)0), 0, &ke, 1, ts)) <= 0) {
192 if (errno(*__errno()) == EINTR4) {
193 close(kq);
194 return;
195 }
196 }
197
198 ctf = ke.udata;
199 if (nevents > 0) {
200 if (ke.filter == EVFILT_READ(-1)) {
201 if (ctf != ltf) {
202 printfname(ctf->fname);
203 ltf = ctf;
204 }
205 clearerr(ctf->fp)(!__isthreaded ? ((void)((ctf->fp)->_flags &= ~(0x0040
|0x0020))) : (clearerr)(ctf->fp));
206 tfprint(ctf->fp);
207 if (ferror(ctf->fp)(!__isthreaded ? (((ctf->fp)->_flags & 0x0040) != 0
) : (ferror)(ctf->fp))) {
208 ierr(ctf->fname);
209 fclose(ctf->fp);
210 warn("Lost file %s", ctf->fname);
211 continue;
212 }
213 (void)fflush(stdout(&__sF[1]));
214 clearerr(ctf->fp)(!__isthreaded ? ((void)((ctf->fp)->_flags &= ~(0x0040
|0x0020))) : (clearerr)(ctf->fp));
215 } else if (ke.filter == EVFILT_VNODE(-4)) {
216 if (ke.fflags & (NOTE_DELETE0x0001 | NOTE_RENAME0x0020)) {
217 /*
218 * File was deleted or renamed.
219 *
220 * Continue to look at it until
221 * a new file reappears with
222 * the same name.
223 */
224 (void) tfreopen(ctf);
225 } else if (ke.fflags & NOTE_TRUNCATE0x0080) {
226 warnx("%s has been truncated, "
227 "resetting.", ctf->fname);
228 fpurge(ctf->fp);
229 rewind(ctf->fp);
230 }
231 }
232 }
233 ts = tfreopen(NULL((void *)0));
234 }
235}
236
237/*
238 * rlines -- display the last offset lines of the file.
239 */
240static int
241rlines(struct tailfile *tf, off_t off)
242{
243 off_t pos;
244 int ch;
245
246 pos = tf->sb.st_size;
247 if (pos == 0)
248 return (0);
249
250 /*
251 * Position before char.
252 * Last char is special, ignore it whether newline or not.
253 */
254 pos -= 2;
255 ch = EOF(-1);
256 for (; off > 0 && pos >= 0; pos--) {
257 /* A seek per char isn't a problem with a smart stdio */
258 if (fseeko(tf[0].fp, pos, SEEK_SET0) == -1) {
259 ierr(tf->fname);
260 return (1);
261 }
262 if ((ch = getc(tf[0].fp)(!__isthreaded ? (--(tf[0].fp)->_r < 0 ? __srget(tf[0].
fp) : (int)(*(tf[0].fp)->_p++)) : (getc)(tf[0].fp))) == '\n')
263 off--;
264 else if (ch == EOF(-1)) {
265 if (ferror(tf[0].fp)(!__isthreaded ? (((tf[0].fp)->_flags & 0x0040) != 0) :
(ferror)(tf[0].fp))) {
266 ierr(tf->fname);
267 return (1);
268 }
269 break;
270 }
271 }
272 /* If we read until start of file, put back last read char */
273 if (pos < 0 && off > 0 && ch != EOF(-1) && ungetc(ch, tf[0].fp) == EOF(-1)) {
274 ierr(tf->fname);
275 return (1);
276 }
277
278 while (!feof(tf[0].fp)(!__isthreaded ? (((tf[0].fp)->_flags & 0x0020) != 0) :
(feof)(tf[0].fp)) && (ch = getc(tf[0].fp)(!__isthreaded ? (--(tf[0].fp)->_r < 0 ? __srget(tf[0].
fp) : (int)(*(tf[0].fp)->_p++)) : (getc)(tf[0].fp))) != EOF(-1))
279 if (putchar(ch)(!__isthreaded ? __sputc(ch, (&__sF[1])) : (putc)(ch, (&
__sF[1]))) == EOF(-1))
280 oerr();
281 if (ferror(tf[0].fp)(!__isthreaded ? (((tf[0].fp)->_flags & 0x0040) != 0) :
(ferror)(tf[0].fp))) {
282 ierr(tf->fname);
283 return (1);
284 }
285
286 return (0);
287}
288
289static inline void
290tfprint(FILE *fp)
291{
292 int ch;
293
294 while (!feof(fp)(!__isthreaded ? (((fp)->_flags & 0x0020) != 0) : (feof
)(fp)) && (ch = getc(fp)(!__isthreaded ? (--(fp)->_r < 0 ? __srget(fp) : (int)(
*(fp)->_p++)) : (getc)(fp))) != EOF(-1))
295 if (putchar(ch)(!__isthreaded ? __sputc(ch, (&__sF[1])) : (putc)(ch, (&
__sF[1]))) == EOF(-1))
296 oerr();
297}
298
299static int
300tfqueue(struct tailfile *tf)
301{
302 struct kevent ke[2];
303 int i = 1;
304
305 if (kq < 0) {
306 errno(*__errno()) = EBADF9;
307 return -1;
308 }
309
310 EV_SET(&(ke[0]), fileno(tf->fp), EVFILT_READ,do { struct kevent *__kevp = (&(ke[0])); (__kevp)->ident
= ((!__isthreaded ? ((tf->fp)->_file) : (fileno)(tf->
fp))); (__kevp)->filter = ((-1)); (__kevp)->flags = (0x0004
| 0x0001 | 0x0020); (__kevp)->fflags = (0); (__kevp)->
data = (0); (__kevp)->udata = (tf); } while(0)
311 EV_ENABLE | EV_ADD | EV_CLEAR, 0, 0, tf)do { struct kevent *__kevp = (&(ke[0])); (__kevp)->ident
= ((!__isthreaded ? ((tf->fp)->_file) : (fileno)(tf->
fp))); (__kevp)->filter = ((-1)); (__kevp)->flags = (0x0004
| 0x0001 | 0x0020); (__kevp)->fflags = (0); (__kevp)->
data = (0); (__kevp)->udata = (tf); } while(0);
312
313 if (S_ISREG(tf->sb.st_mode)((tf->sb.st_mode & 0170000) == 0100000)) {
314 i = 2;
315 EV_SET(&(ke[1]), fileno(tf->fp), EVFILT_VNODE,do { struct kevent *__kevp = (&(ke[1])); (__kevp)->ident
= ((!__isthreaded ? ((tf->fp)->_file) : (fileno)(tf->
fp))); (__kevp)->filter = ((-4)); (__kevp)->flags = (0x0004
| 0x0001 | 0x0020); (__kevp)->fflags = (0x0001 | 0x0020 |
0x0080); (__kevp)->data = (0); (__kevp)->udata = (tf);
} while(0)
316 EV_ENABLE | EV_ADD | EV_CLEAR,do { struct kevent *__kevp = (&(ke[1])); (__kevp)->ident
= ((!__isthreaded ? ((tf->fp)->_file) : (fileno)(tf->
fp))); (__kevp)->filter = ((-4)); (__kevp)->flags = (0x0004
| 0x0001 | 0x0020); (__kevp)->fflags = (0x0001 | 0x0020 |
0x0080); (__kevp)->data = (0); (__kevp)->udata = (tf);
} while(0)
317 NOTE_DELETE | NOTE_RENAME | NOTE_TRUNCATE,do { struct kevent *__kevp = (&(ke[1])); (__kevp)->ident
= ((!__isthreaded ? ((tf->fp)->_file) : (fileno)(tf->
fp))); (__kevp)->filter = ((-4)); (__kevp)->flags = (0x0004
| 0x0001 | 0x0020); (__kevp)->fflags = (0x0001 | 0x0020 |
0x0080); (__kevp)->data = (0); (__kevp)->udata = (tf);
} while(0)
318 0, tf)do { struct kevent *__kevp = (&(ke[1])); (__kevp)->ident
= ((!__isthreaded ? ((tf->fp)->_file) : (fileno)(tf->
fp))); (__kevp)->filter = ((-4)); (__kevp)->flags = (0x0004
| 0x0001 | 0x0020); (__kevp)->fflags = (0x0001 | 0x0020 |
0x0080); (__kevp)->data = (0); (__kevp)->udata = (tf);
} while(0);
319 }
320 if (kevent(kq, ke, i, NULL((void *)0), 0, NULL((void *)0)) == -1) {
321 ierr(tf->fname);
322 return -1;
323 }
324 return 0;
325}
326
327#define AFILESINCR8 8
328static const struct timespec *
329tfreopen(struct tailfile *tf) {
330 static struct tailfile **reopen = NULL((void *)0);
331 static int nfiles = 0, afiles = 0;
332 static const struct timespec ts = {1, 0};
333
334 struct stat sb;
335 struct tailfile **treopen, *ttf;
336 int i;
337
338 if (tf && !(tf->fp == stdin(&__sF[0])) &&
339 ((stat(tf->fname, &sb) != 0) || sb.st_ino != tf->sb.st_ino)) {
340 if (afiles < ++nfiles) {
341 afiles += AFILESINCR8;
342 treopen = reallocarray(reopen, afiles, sizeof(*reopen));
343 if (treopen)
344 reopen = treopen;
345 else
346 afiles -= AFILESINCR8;
347 }
348 if (nfiles <= afiles) {
349 for (i = 0; i < nfiles - 1; i++)
350 if (strcmp(reopen[i]->fname, tf->fname) == 0)
351 break;
352 if (i < nfiles - 1)
353 nfiles--;
354 else
355 reopen[nfiles-1] = tf;
356 } else {
357 warnx("Lost track of %s", tf->fname);
358 nfiles--;
359 }
360 }
361
362 for (i = 0; i < nfiles; i++) {
363 ttf = reopen[i];
364 if (stat(ttf->fname, &sb) == -1)
365 continue;
366 if (sb.st_ino != ttf->sb.st_ino) {
367 (void) memcpy(&(ttf->sb), &sb, sizeof(ttf->sb));
368 ttf->fp = freopen(ttf->fname, "r", ttf->fp);
369 if (ttf->fp == NULL((void *)0))
370 ierr(ttf->fname);
371 else {
372 warnx("%s has been replaced, reopening.",
373 ttf->fname);
374 tfqueue(ttf);
375 }
376 }
377 reopen[i] = reopen[--nfiles];
378 }
379
380 return nfiles ? &ts : NULL((void *)0);
381}