Movatterモバイル変換

[0]ホーム
URL:

Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly

 Sign up
Appearance settings

Commit4d6ad31

Browse files
committed
Provide overflow safe integer math inline functions.
It's not easy to get signed integer overflow checks correct andfast. Therefore abstract the necessary infrastructure into a commonheader providing addition, subtraction and multiplication for 16, 32,64 bit signed integers.The new macros aren't yet used, but a followup commit will convertseveral open coded overflow checks.Author: Andres Freund, with some code stolen from Greg StarkReviewed-By: Robert HaasDiscussion:https://postgr.es/m/20171024103954.ztmatprlglz3rwke@alap3.anarazel.de
1 parent95b5235 commit4d6ad31

File tree

6 files changed

+304
-0
lines changed

6 files changed

+304
-0
lines changed

‎config/c-compiler.m4‎

Lines changed: 22 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -299,6 +299,28 @@ fi])# PGAC_C_BUILTIN_CONSTANT_P
299299

300300

301301

302+
# PGAC_C_BUILTIN_OP_OVERFLOW
303+
# -------------------------
304+
# Check if the C compiler understands __builtin_$op_overflow(),
305+
# and define HAVE__BUILTIN_OP_OVERFLOW if so.
306+
#
307+
# Check for the most complicated case, 64 bit multiplication, as a
308+
# proxy for all of the operations.
309+
AC_DEFUN([PGAC_C_BUILTIN_OP_OVERFLOW],
310+
[AC_CACHE_CHECK(for__builtin_mul_overflow,pgac_cv__builtin_op_overflow,
311+
[AC_COMPILE_IFELSE([AC_LANG_PROGRAM([],
312+
[PG_INT64_TYPE result;
313+
__builtin_mul_overflow((PG_INT64_TYPE) 1, (PG_INT64_TYPE) 2, &result);]
314+
)],
315+
[pgac_cv__builtin_op_overflow=yes],
316+
[pgac_cv__builtin_op_overflow=no])])
317+
if test x"$pgac_cv__builtin_op_overflow" = xyes ; then
318+
AC_DEFINE(HAVE__BUILTIN_OP_OVERFLOW,1,
319+
[Define to 1 if your compiler understands __builtin_$op_overflow.])
320+
fi])# PGAC_C_BUILTIN_OP_OVERFLOW
321+
322+
323+
302324
# PGAC_C_BUILTIN_UNREACHABLE
303325
# --------------------------
304326
# Check if the C compiler understands __builtin_unreachable(),

‎configure‎

Lines changed: 33 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -14472,6 +14472,39 @@ esac
1447214472

1447314473
fi
1447414474

14475+
{$as_echo"$as_me:${as_lineno-$LINENO}: checking for __builtin_mul_overflow">&5
14476+
$as_echo_n"checking for __builtin_mul_overflow...">&6; }
14477+
if${pgac_cv__builtin_op_overflow+:}false;then:
14478+
$as_echo_n"(cached)">&6
14479+
else
14480+
cat confdefs.h -<<_ACEOF >conftest.$ac_ext
14481+
/* end confdefs.h. */
14482+
14483+
int
14484+
main ()
14485+
{
14486+
PG_INT64_TYPE result;
14487+
__builtin_mul_overflow((PG_INT64_TYPE) 1, (PG_INT64_TYPE) 2, &result);
14488+
14489+
;
14490+
return 0;
14491+
}
14492+
_ACEOF
14493+
if ac_fn_c_try_compile"$LINENO";then:
14494+
pgac_cv__builtin_op_overflow=yes
14495+
else
14496+
pgac_cv__builtin_op_overflow=no
14497+
fi
14498+
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
14499+
fi
14500+
{$as_echo"$as_me:${as_lineno-$LINENO}: result:$pgac_cv__builtin_op_overflow">&5
14501+
$as_echo"$pgac_cv__builtin_op_overflow">&6; }
14502+
iftest x"$pgac_cv__builtin_op_overflow" = xyes;then
14503+
14504+
$as_echo"#define HAVE__BUILTIN_OP_OVERFLOW 1">>confdefs.h
14505+
14506+
fi
14507+
1447514508
# Check size of void *, size_t (enables tweaks for > 32bit address space)
1447614509
# The cast to long int works around a bug in the HP C Compiler
1447714510
# version HP92453-01 B.11.11.23709.GP, which incorrectly rejects

‎configure.in‎

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1770,6 +1770,10 @@ if test $pgac_need_repl_snprintf = yes; then
17701770
AC_LIBOBJ(snprintf)
17711771
fi
17721772

1773+
# has to be down here, rather than with the other builtins, because
1774+
# the test uses PG_INT64_TYPE.
1775+
PGAC_C_BUILTIN_OP_OVERFLOW
1776+
17731777
# Check size of void *, size_t (enables tweaks for > 32bit address space)
17741778
AC_CHECK_SIZEOF([void *])
17751779
AC_CHECK_SIZEOF([size_t])

‎src/include/common/int.h‎

Lines changed: 239 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,239 @@
1+
/*-------------------------------------------------------------------------
2+
*
3+
* int.h
4+
* Routines to perform integer math, while checking for overflows.
5+
*
6+
* The routines in this file are intended to be well defined C, without
7+
* relying on compiler flags like -fwrapv.
8+
*
9+
* To reduce the overhead of these routines try to use compiler intrinsics
10+
* where available. That's not that important for the 16, 32 bit cases, but
11+
* the 64 bit cases can be considerably faster with intrinsics. In case no
12+
* intrinsics are available 128 bit math is used where available.
13+
*
14+
* Copyright (c) 2017, PostgreSQL Global Development Group
15+
*
16+
* src/include/common/int.h
17+
*
18+
*-------------------------------------------------------------------------
19+
*/
20+
#ifndefCOMMON_INT_H
21+
#defineCOMMON_INT_H
22+
23+
/*
24+
* If a + b overflows, return true, otherwise store the result of a + b into
25+
* *result. The content of *result is implementation defined in case of
26+
* overflow.
27+
*/
28+
staticinlinebool
29+
pg_add_s16_overflow(int16a,int16b,int16*result)
30+
{
31+
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
32+
return__builtin_add_overflow(a,b,result);
33+
#else
34+
int32res= (int32)a+ (int32)b;
35+
36+
if (res>PG_INT16_MAX||res<PG_INT16_MIN)
37+
return true;
38+
*result= (int16)res;
39+
return false;
40+
#endif
41+
}
42+
43+
/*
44+
* If a - b overflows, return true, otherwise store the result of a + b into
45+
* *result. The content of *result is implementation defined in case of
46+
* overflow.
47+
*/
48+
staticinlinebool
49+
pg_sub_s16_overflow(int16a,int16b,int16*result)
50+
{
51+
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
52+
return__builtin_sub_overflow(a,b,result);
53+
#else
54+
int32res= (int32)a- (int32)b;
55+
56+
if (res>PG_INT16_MAX||res<PG_INT16_MIN)
57+
return true;
58+
*result= (int16)res;
59+
return false;
60+
#endif
61+
}
62+
63+
/*
64+
* If a * b overflows, return true, otherwise store the result of a + b into
65+
* *result. The content of *result is implementation defined in case of
66+
* overflow.
67+
*/
68+
staticinlinebool
69+
pg_mul_s16_overflow(int16a,int16b,int16*result)
70+
{
71+
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
72+
return__builtin_mul_overflow(a,b,result);
73+
#else
74+
int32res= (int32)a* (int32)b;
75+
76+
if (res>PG_INT16_MAX||res<PG_INT16_MIN)
77+
return true;
78+
*result= (int16)res;
79+
return false;
80+
#endif
81+
}
82+
83+
/*
84+
* If a + b overflows, return true, otherwise store the result of a + b into
85+
* *result. The content of *result is implementation defined in case of
86+
* overflow.
87+
*/
88+
staticinlinebool
89+
pg_add_s32_overflow(int32a,int32b,int32*result)
90+
{
91+
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
92+
return__builtin_add_overflow(a,b,result);
93+
#else
94+
int64res= (int64)a+ (int64)b;
95+
96+
if (res>PG_INT32_MAX||res<PG_INT32_MIN)
97+
return true;
98+
*result= (int32)res;
99+
return false;
100+
#endif
101+
}
102+
103+
/*
104+
* If a - b overflows, return true, otherwise store the result of a + b into
105+
* *result. The content of *result is implementation defined in case of
106+
* overflow.
107+
*/
108+
staticinlinebool
109+
pg_sub_s32_overflow(int32a,int32b,int32*result)
110+
{
111+
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
112+
return__builtin_sub_overflow(a,b,result);
113+
#else
114+
int64res= (int64)a- (int64)b;
115+
116+
if (res>PG_INT32_MAX||res<PG_INT32_MIN)
117+
return true;
118+
*result= (int32)res;
119+
return false;
120+
#endif
121+
}
122+
123+
/*
124+
* If a * b overflows, return true, otherwise store the result of a + b into
125+
* *result. The content of *result is implementation defined in case of
126+
* overflow.
127+
*/
128+
staticinlinebool
129+
pg_mul_s32_overflow(int32a,int32b,int32*result)
130+
{
131+
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
132+
return__builtin_mul_overflow(a,b,result);
133+
#else
134+
int64res= (int64)a* (int64)b;
135+
136+
if (res>PG_INT32_MAX||res<PG_INT32_MIN)
137+
return true;
138+
*result= (int32)res;
139+
return false;
140+
#endif
141+
}
142+
143+
/*
144+
* If a + b overflows, return true, otherwise store the result of a + b into
145+
* *result. The content of *result is implementation defined in case of
146+
* overflow.
147+
*/
148+
staticinlinebool
149+
pg_add_s64_overflow(int64a,int64b,int64*result)
150+
{
151+
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
152+
return__builtin_add_overflow(a,b,result);
153+
#elif defined(HAVE_INT128)
154+
int128res= (int128)a+ (int128)b;
155+
156+
if (res>PG_INT64_MAX||res<PG_INT64_MIN)
157+
return true;
158+
*result= (int64)res;
159+
return false;
160+
#else
161+
if ((a>0&&b>0&&a>PG_INT64_MAX-b)||
162+
(a<0&&b<0&&a<PG_INT64_MIN-b))
163+
return true;
164+
*result=a+b;
165+
return false;
166+
#endif
167+
}
168+
169+
/*
170+
* If a - b overflows, return true, otherwise store the result of a + b into
171+
* *result. The content of *result is implementation defined in case of
172+
* overflow.
173+
*/
174+
staticinlinebool
175+
pg_sub_s64_overflow(int64a,int64b,int64*result)
176+
{
177+
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
178+
return__builtin_sub_overflow(a,b,result);
179+
#elif defined(HAVE_INT128)
180+
int128res= (int128)a- (int128)b;
181+
182+
if (res>PG_INT64_MAX||res<PG_INT64_MIN)
183+
return true;
184+
*result= (int64)res;
185+
return false;
186+
#else
187+
if ((a<0&&b>0&&a<PG_INT64_MIN+b)||
188+
(a>0&&b<0&&a>PG_INT64_MAX+b))
189+
return true;
190+
*result=a-b;
191+
return false;
192+
#endif
193+
}
194+
195+
/*
196+
* If a * b overflows, return true, otherwise store the result of a + b into
197+
* *result. The content of *result is implementation defined in case of
198+
* overflow.
199+
*/
200+
staticinlinebool
201+
pg_mul_s64_overflow(int64a,int64b,int64*result)
202+
{
203+
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
204+
return__builtin_mul_overflow(a,b,result);
205+
#elif defined(HAVE_INT128)
206+
int128res= (int128)a* (int128)b;
207+
208+
if (res>PG_INT64_MAX||res<PG_INT64_MIN)
209+
return true;
210+
*result= (int64)res;
211+
return false;
212+
#else
213+
/*
214+
* Overflow can only happen if at least one value is outside the range
215+
* sqrt(min)..sqrt(max) so check that first as the division can be quite a
216+
* bit more expensive than the multiplication.
217+
*
218+
* Multiplying by 0 or 1 can't overflow of course and checking for 0
219+
* separately avoids any risk of dividing by 0. Be careful about dividing
220+
* INT_MIN by -1 also, note reversing the a and b to ensure we're always
221+
* dividing it by a positive value.
222+
*
223+
*/
224+
if ((a>PG_INT32_MAX||a<PG_INT32_MIN||
225+
b>PG_INT32_MAX||b<PG_INT32_MIN)&&
226+
a!=0&&a!=1&&b!=0&&b!=1&&
227+
((a>0&&b>0&&a>PG_INT64_MAX /b)||
228+
(a>0&&b<0&&b<PG_INT64_MIN /a)||
229+
(a<0&&b>0&&a<PG_INT64_MIN /b)||
230+
(a<0&&b<0&&a<PG_INT64_MAX /b)))
231+
{
232+
return true;
233+
}
234+
*result=a*b;
235+
return false;
236+
#endif
237+
}
238+
239+
#endif/* COMMON_INT_H */

‎src/include/pg_config.h.in‎

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -690,6 +690,9 @@
690690
/* Define to 1 if your compiler understands __builtin_constant_p. */
691691
#undef HAVE__BUILTIN_CONSTANT_P
692692

693+
/* Define to 1 if your compiler understands __builtin_$op_overflow. */
694+
#undef HAVE__BUILTIN_OP_OVERFLOW
695+
693696
/* Define to 1 if your compiler understands __builtin_types_compatible_p. */
694697
#undef HAVE__BUILTIN_TYPES_COMPATIBLE_P
695698

‎src/include/pg_config.h.win32‎

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -515,6 +515,9 @@
515515
/* Define to 1 if your compiler understands __builtin_constant_p. */
516516
/* #undef HAVE__BUILTIN_CONSTANT_P */
517517

518+
/* Define to 1 if your compiler understands __builtin_$op_overflow. */
519+
/* #undef HAVE__BUILTIN_OP_OVERFLOW */
520+
518521
/* Define to 1 if your compiler understands __builtin_types_compatible_p. */
519522
/* #undef HAVE__BUILTIN_TYPES_COMPATIBLE_P */
520523

0 commit comments

Comments
 (0)
[8]ページ先頭
©2009-2025 Movatter.jp