Bug Summary

File:src/lib/libc/stdlib/merge.c
Warning:line 260, column 16
Dereference of null pointer

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 merge.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/lib/libc/obj -resource-dir /usr/local/lib/clang/13.0.0 -include namespace.h -I /usr/src/lib/libc/include -I /usr/src/lib/libc/hidden -D __LIBC__ -D APIWARN -D YP -I /usr/src/lib/libc/yp -I /usr/src/lib/libc -I /usr/src/lib/libc/gdtoa -I /usr/src/lib/libc/arch/amd64/gdtoa -D INFNAN_CHECK -D MULTIPLE_THREADS -D NO_FENV_H -D USE_LOCALE -I /usr/src/lib/libc -I /usr/src/lib/libc/citrus -D RESOLVSORT -D FLOATING_POINT -D PRINTF_WIDE_CHAR -D SCANF_WIDE_CHAR -D FUTEX -internal-isystem /usr/local/lib/clang/13.0.0/include -internal-externc-isystem /usr/include -O2 -fdebug-compilation-dir=/usr/src/lib/libc/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/lib/libc/stdlib/merge.c
1/* $OpenBSD: merge.c,v 1.10 2015/06/21 03:20:56 millert Exp $ */
2/*-
3 * Copyright (c) 1992, 1993
4 * The Regents of the University of California. All rights reserved.
5 *
6 * This code is derived from software contributed to Berkeley by
7 * Peter McIlroy.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 * 3. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34/*
35 * Hybrid exponential search/linear search merge sort with hybrid
36 * natural/pairwise first pass. Requires about .3% more comparisons
37 * for random data than LSMS with pairwise first pass alone.
38 * It works for objects as small as two bytes.
39 */
40
41#define NATURAL
42#define THRESHOLD16 16 /* Best choice for natural merge cut-off. */
43
44/* #define NATURAL to get hybrid natural merge.
45 * (The default is pairwise merging.)
46 */
47
48#include <sys/types.h>
49
50#include <errno(*__errno()).h>
51#include <stdlib.h>
52#include <string.h>
53
54static void setup(u_char *, u_char *, size_t, size_t, int (*)());
55static void insertionsort(u_char *, size_t, size_t, int (*)());
56
57#define ISIZEsizeof(int) sizeof(int)
58#define PSIZEsizeof(u_char *) sizeof(u_char *)
59#define ICOPY_LIST(src, dst, last)do *(int*)dst = *(int*)src, src += sizeof(int), dst += sizeof
(int); while(src < last) \
60 do \
61 *(int*)dst = *(int*)src, src += ISIZEsizeof(int), dst += ISIZEsizeof(int); \
62 while(src < last)
63#define ICOPY_ELT(src, dst, i)do *(int*) dst = *(int*) src, src += sizeof(int), dst += sizeof
(int); while (i -= sizeof(int)) \
64 do \
65 *(int*) dst = *(int*) src, src += ISIZEsizeof(int), dst += ISIZEsizeof(int); \
66 while (i -= ISIZEsizeof(int))
67
68#define CCOPY_LIST(src, dst, last)do *dst++ = *src++; while (src < last) \
69 do \
70 *dst++ = *src++; \
71 while (src < last)
72#define CCOPY_ELT(src, dst, i)do *dst++ = *src++; while (i -= 1) \
73 do \
74 *dst++ = *src++; \
75 while (i -= 1)
76
77/*
78 * Find the next possible pointer head. (Trickery for forcing an array
79 * to do double duty as a linked list when objects do not align with word
80 * boundaries.
81 */
82/* Assumption: PSIZE is a power of 2. */
83#define EVAL(p)(u_char **) ((u_char *)0 + (((u_char *)p + sizeof(u_char *) -
1 - (u_char *) 0) & ~(sizeof(u_char *) - 1))) (u_char **) \
84 ((u_char *)0 + \
85 (((u_char *)p + PSIZEsizeof(u_char *) - 1 - (u_char *) 0) & ~(PSIZEsizeof(u_char *) - 1)))
86
87/*
88 * Arguments are as for qsort.
89 */
90int
91mergesort(void *base, size_t nmemb, size_t size,
92 int (*cmp)(const void *, const void *))
93{
94 int i, sense;
95 int big, iflag;
96 u_char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2;
97 u_char *list2, *list1, *p2, *p, *last, **p1;
98
99 if (size < PSIZEsizeof(u_char *) / 2) { /* Pointers must fit into 2 * size. */
1
Assuming the condition is false
→
2
←
Taking false branch
→
100 errno(*__errno()) = EINVAL22;
101 return (-1);
102 }
103
104 if (nmemb == 0)
3
←
Assuming 'nmemb' is not equal to 0
→
4
←
Taking false branch
→
105 return (0);
106
107 /*
108 * XXX
109 * Stupid subtraction for the Cray.
110 */
111 iflag = 0;
112 if (!(size % ISIZEsizeof(int)) && !(((char *)base - (char *)0) % ISIZEsizeof(int)))
5
←
Assuming the condition is false
→
113 iflag = 1;
114
115 if ((list2 = malloc(nmemb * size + PSIZEsizeof(u_char *))) == NULL((void *)0))
6
←
Assuming the condition is false
→
7
←
Taking false branch
→
116 return (-1);
117
118 list1 = base;
119 setup(list1, list2, nmemb, size, cmp);
8
←
Calling 'setup'
→
120 last = list2 + nmemb * size;
121 i = big = 0;
122 while (*EVAL(list2)(u_char **) ((u_char *)0 + (((u_char *)list2 + sizeof(u_char *
) - 1 - (u_char *) 0) & ~(sizeof(u_char *) - 1))) != last) {
123 l2 = list1;
124 p1 = EVAL(list1)(u_char **) ((u_char *)0 + (((u_char *)list1 + sizeof(u_char *
) - 1 - (u_char *) 0) & ~(sizeof(u_char *) - 1)));
125 for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)(u_char **) ((u_char *)0 + (((u_char *)l2 + sizeof(u_char *) -
1 - (u_char *) 0) & ~(sizeof(u_char *) - 1)))) {
126 p2 = *EVAL(p2)(u_char **) ((u_char *)0 + (((u_char *)p2 + sizeof(u_char *) -
1 - (u_char *) 0) & ~(sizeof(u_char *) - 1)));
127 f1 = l2;
128 f2 = l1 = list1 + (p2 - list2);
129 if (p2 != last)
130 p2 = *EVAL(p2)(u_char **) ((u_char *)0 + (((u_char *)p2 + sizeof(u_char *) -
1 - (u_char *) 0) & ~(sizeof(u_char *) - 1)));
131 l2 = list1 + (p2 - list2);
132 while (f1 < l1 && f2 < l2) {
133 if ((*cmp)(f1, f2) <= 0) {
134 q = f2;
135 b = f1, t = l1;
136 sense = -1;
137 } else {
138 q = f1;
139 b = f2, t = l2;
140 sense = 0;
141 }
142 if (!big) { /* here i = 0 */
143 while ((b += size) < t && cmp(q, b) >sense)
144 if (++i == 6) {
145 big = 1;
146 goto EXPONENTIAL;
147 }
148 } else {
149EXPONENTIAL: for (i = size; ; i <<= 1)
150 if ((p = (b + i)) >= t) {
151 if ((p = t - size) > b &&
152 (*cmp)(q, p) <= sense)
153 t = p;
154 else
155 b = p;
156 break;
157 } else if ((*cmp)(q, p) <= sense) {
158 t = p;
159 if (i == size)
160 big = 0;
161 goto FASTCASE;
162 } else
163 b = p;
164 while (t > b+size) {
165 i = (((t - b) / size) >> 1) * size;
166 if ((*cmp)(q, p = b + i) <= sense)
167 t = p;
168 else
169 b = p;
170 }
171 goto COPY;
172FASTCASE: while (i > size)
173 if ((*cmp)(q,
174 p = b + (i >>= 1)) <= sense)
175 t = p;
176 else
177 b = p;
178COPY: b = t;
179 }
180 i = size;
181 if (q == f1) {
182 if (iflag) {
183 ICOPY_LIST(f2, tp2, b)do *(int*)tp2 = *(int*)f2, f2 += sizeof(int), tp2 += sizeof(int
); while(f2 < b);
184 ICOPY_ELT(f1, tp2, i)do *(int*) tp2 = *(int*) f1, f1 += sizeof(int), tp2 += sizeof
(int); while (i -= sizeof(int));
185 } else {
186 CCOPY_LIST(f2, tp2, b)do *tp2++ = *f2++; while (f2 < b);
187 CCOPY_ELT(f1, tp2, i)do *tp2++ = *f1++; while (i -= 1);
188 }
189 } else {
190 if (iflag) {
191 ICOPY_LIST(f1, tp2, b)do *(int*)tp2 = *(int*)f1, f1 += sizeof(int), tp2 += sizeof(int
); while(f1 < b);
192 ICOPY_ELT(f2, tp2, i)do *(int*) tp2 = *(int*) f2, f2 += sizeof(int), tp2 += sizeof
(int); while (i -= sizeof(int));
193 } else {
194 CCOPY_LIST(f1, tp2, b)do *tp2++ = *f1++; while (f1 < b);
195 CCOPY_ELT(f2, tp2, i)do *tp2++ = *f2++; while (i -= 1);
196 }
197 }
198 }
199 if (f2 < l2) {
200 if (iflag)
201 ICOPY_LIST(f2, tp2, l2)do *(int*)tp2 = *(int*)f2, f2 += sizeof(int), tp2 += sizeof(int
); while(f2 < l2);
202 else
203 CCOPY_LIST(f2, tp2, l2)do *tp2++ = *f2++; while (f2 < l2);
204 } else if (f1 < l1) {
205 if (iflag)
206 ICOPY_LIST(f1, tp2, l1)do *(int*)tp2 = *(int*)f1, f1 += sizeof(int), tp2 += sizeof(int
); while(f1 < l1);
207 else
208 CCOPY_LIST(f1, tp2, l1)do *tp2++ = *f1++; while (f1 < l1);
209 }
210 *p1 = l2;
211 }
212 tp2 = list1; /* swap list1, list2 */
213 list1 = list2;
214 list2 = tp2;
215 last = list2 + nmemb*size;
216 }
217 if (base == list2) {
218 memmove(list2, list1, nmemb*size);
219 list2 = list1;
220 }
221 free(list2);
222 return (0);
223}
224
225#define swap(a, b){ s = b; i = size; do { tmp = *a; *a++ = *s; *s++ = tmp; } while
(--i); a -= size; } { \
226 s = b; \
227 i = size; \
228 do { \
229 tmp = *a; *a++ = *s; *s++ = tmp; \
230 } while (--i); \
231 a -= size; \
232 }
233#define reverse(bot, top){ s = top; do { i = size; do { tmp = *bot; *bot++ = *s; *s++ =
tmp; } while (--i); s -= size2; } while(bot < s); } { \
234 s = top; \
235 do { \
236 i = size; \
237 do { \
238 tmp = *bot; *bot++ = *s; *s++ = tmp; \
239 } while (--i); \
240 s -= size2; \
241 } while(bot < s); \
242}
243
244/*
245 * Optional hybrid natural/pairwise first pass. Eats up list1 in runs of
246 * increasing order, list2 in a corresponding linked list. Checks for runs
247 * when THRESHOLD/2 pairs compare with same sense. (Only used when NATURAL
248 * is defined. Otherwise simple pairwise merging is used.)
249 */
250void
251setup(u_char *list1, u_char *list2, size_t n, size_t size,
252 int (*cmp)(const void *, const void *))
253{
254 int i, length, size2, sense;
255 u_char tmp, *f1, *f2, *s, *l2, *last, *p2;
256
257 size2 = size*2;
258 if (n <= 5) {
9
←
Assuming 'n' is <= 5
→
10
←
Taking true branch
→
259 insertionsort(list1, n, size, cmp);
260 *EVAL(list2)(u_char **) ((u_char *)0 + (((u_char *)list2 + sizeof(u_char *
) - 1 - (u_char *) 0) & ~(sizeof(u_char *) - 1))) = (u_char*) list2 + n*size;
11
←
Dereference of null pointer
261 return;
262 }
263 /*
264 * Avoid running pointers out of bounds; limit n to evens
265 * for simplicity.
266 */
267 i = 4 + (n & 1);
268 insertionsort(list1 + (n - i) * size, i, size, cmp);
269 last = list1 + size * (n - i);
270 *EVAL(list2 + (last - list1))(u_char **) ((u_char *)0 + (((u_char *)list2 + (last - list1)
+ sizeof(u_char *) - 1 - (u_char *) 0) & ~(sizeof(u_char
*) - 1))) = list2 + n * size;
271
272#ifdef NATURAL
273 p2 = list2;
274 f1 = list1;
275 sense = (cmp(f1, f1 + size) > 0);
276 for (; f1 < last; sense = !sense) {
277 length = 2;
278 /* Find pairs with same sense. */
279 for (f2 = f1 + size2; f2 < last; f2 += size2) {
280 if ((cmp(f2, f2+ size) > 0) != sense)
281 break;
282 length += 2;
283 }
284 if (length < THRESHOLD16) { /* Pairwise merge */
285 do {
286 p2 = *EVAL(p2)(u_char **) ((u_char *)0 + (((u_char *)p2 + sizeof(u_char *) -
1 - (u_char *) 0) & ~(sizeof(u_char *) - 1))) = f1 + size2 - list1 + list2;
287 if (sense > 0)
288 swap (f1, f1 + size){ s = f1 + size; i = size; do { tmp = *f1; *f1++ = *s; *s++ =
tmp; } while (--i); f1 -= size; };
289 } while ((f1 += size2) < f2);
290 } else { /* Natural merge */
291 l2 = f2;
292 for (f2 = f1 + size2; f2 < l2; f2 += size2) {
293 if ((cmp(f2-size, f2) > 0) != sense) {
294 p2 = *EVAL(p2)(u_char **) ((u_char *)0 + (((u_char *)p2 + sizeof(u_char *) -
1 - (u_char *) 0) & ~(sizeof(u_char *) - 1))) = f2 - list1 + list2;
295 if (sense > 0)
296 reverse(f1, f2-size){ s = f2-size; do { i = size; do { tmp = *f1; *f1++ = *s; *s++
= tmp; } while (--i); s -= size2; } while(f1 < s); };
297 f1 = f2;
298 }
299 }
300 if (sense > 0)
301 reverse (f1, f2-size){ s = f2-size; do { i = size; do { tmp = *f1; *f1++ = *s; *s++
= tmp; } while (--i); s -= size2; } while(f1 < s); };
302 f1 = f2;
303 if (f2 < last || cmp(f2 - size, f2) > 0)
304 p2 = *EVAL(p2)(u_char **) ((u_char *)0 + (((u_char *)p2 + sizeof(u_char *) -
1 - (u_char *) 0) & ~(sizeof(u_char *) - 1))) = f2 - list1 + list2;
305 else
306 p2 = *EVAL(p2)(u_char **) ((u_char *)0 + (((u_char *)p2 + sizeof(u_char *) -
1 - (u_char *) 0) & ~(sizeof(u_char *) - 1))) = list2 + n*size;
307 }
308 }
309#else /* pairwise merge only. */
310 for (f1 = list1, p2 = list2; f1 < last; f1 += size2) {
311 p2 = *EVAL(p2)(u_char **) ((u_char *)0 + (((u_char *)p2 + sizeof(u_char *) -
1 - (u_char *) 0) & ~(sizeof(u_char *) - 1))) = p2 + size2;
312 if (cmp (f1, f1 + size) > 0)
313 swap(f1, f1 + size){ s = f1 + size; i = size; do { tmp = *f1; *f1++ = *s; *s++ =
tmp; } while (--i); f1 -= size; };
314 }
315#endif /* NATURAL */
316}
317
318/*
319 * This is to avoid out-of-bounds addresses in sorting the
320 * last 4 elements.
321 */
322static void
323insertionsort(u_char *a, size_t n, size_t size,
324 int (*cmp)(const void *, const void *))
325{
326 u_char *ai, *s, *t, *u, tmp;
327 int i;
328
329 for (ai = a+size; --n >= 1; ai += size)
330 for (t = ai; t > a; t -= size) {
331 u = t - size;
332 if (cmp(u, t) <= 0)
333 break;
334 swap(u, t){ s = t; i = size; do { tmp = *u; *u++ = *s; *s++ = tmp; } while
(--i); u -= size; };
335 }
336}