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Commit6d7dc53

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Return implementation defined value if pg_$op_s$bit_overflow overflows.
Some older compilers otherwise sometimes complain about undefinedvalues, even though the return value should not be used in theoverflow case. We assume that any decent compiler will optimize awaythe unnecessary assignment in performance critical cases.We do not want to restrain the returned value to a specific value,e.g. 0 or the wrapped-around value, because some fast ways toimplement overflow detecting math do not easily allow forthat (e.g. msvc intrinsics). As the function documentation alreadydocuments the returned value in case of intrinsics to beimplementation defined, no documentation has to be updated.Per complaint from Tom Lane and his buildfarm member prairiedog.Author: Andres FreundDiscussion:https://postgr.es/m/18169.1513958454@sss.pgh.pa.us
1 parent9a725f7 commit6d7dc53

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‎src/include/common/int.h

Lines changed: 34 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -34,7 +34,10 @@ pg_add_s16_overflow(int16 a, int16 b, int16 *result)
3434
int32res= (int32)a+ (int32)b;
3535

3636
if (res>PG_INT16_MAX||res<PG_INT16_MIN)
37+
{
38+
*result=0x5EED;/* to avoid spurious warnings */
3739
return true;
40+
}
3841
*result= (int16)res;
3942
return false;
4043
#endif
@@ -54,7 +57,10 @@ pg_sub_s16_overflow(int16 a, int16 b, int16 *result)
5457
int32res= (int32)a- (int32)b;
5558

5659
if (res>PG_INT16_MAX||res<PG_INT16_MIN)
60+
{
61+
*result=0x5EED;/* to avoid spurious warnings */
5762
return true;
63+
}
5864
*result= (int16)res;
5965
return false;
6066
#endif
@@ -74,7 +80,10 @@ pg_mul_s16_overflow(int16 a, int16 b, int16 *result)
7480
int32res= (int32)a* (int32)b;
7581

7682
if (res>PG_INT16_MAX||res<PG_INT16_MIN)
83+
{
84+
*result=0x5EED;/* to avoid spurious warnings */
7785
return true;
86+
}
7887
*result= (int16)res;
7988
return false;
8089
#endif
@@ -94,7 +103,10 @@ pg_add_s32_overflow(int32 a, int32 b, int32 *result)
94103
int64res= (int64)a+ (int64)b;
95104

96105
if (res>PG_INT32_MAX||res<PG_INT32_MIN)
106+
{
107+
*result=0x5EED;/* to avoid spurious warnings */
97108
return true;
109+
}
98110
*result= (int32)res;
99111
return false;
100112
#endif
@@ -114,7 +126,10 @@ pg_sub_s32_overflow(int32 a, int32 b, int32 *result)
114126
int64res= (int64)a- (int64)b;
115127

116128
if (res>PG_INT32_MAX||res<PG_INT32_MIN)
129+
{
130+
*result=0x5EED;/* to avoid spurious warnings */
117131
return true;
132+
}
118133
*result= (int32)res;
119134
return false;
120135
#endif
@@ -134,7 +149,10 @@ pg_mul_s32_overflow(int32 a, int32 b, int32 *result)
134149
int64res= (int64)a* (int64)b;
135150

136151
if (res>PG_INT32_MAX||res<PG_INT32_MIN)
152+
{
153+
*result=0x5EED;/* to avoid spurious warnings */
137154
return true;
155+
}
138156
*result= (int32)res;
139157
return false;
140158
#endif
@@ -154,13 +172,19 @@ pg_add_s64_overflow(int64 a, int64 b, int64 *result)
154172
int128res= (int128)a+ (int128)b;
155173

156174
if (res>PG_INT64_MAX||res<PG_INT64_MIN)
175+
{
176+
*result=0x5EED;/* to avoid spurious warnings */
157177
return true;
178+
}
158179
*result= (int64)res;
159180
return false;
160181
#else
161182
if ((a>0&&b>0&&a>PG_INT64_MAX-b)||
162183
(a<0&&b<0&&a<PG_INT64_MIN-b))
184+
{
185+
*result=0x5EED;/* to avoid spurious warnings */
163186
return true;
187+
}
164188
*result=a+b;
165189
return false;
166190
#endif
@@ -180,13 +204,19 @@ pg_sub_s64_overflow(int64 a, int64 b, int64 *result)
180204
int128res= (int128)a- (int128)b;
181205

182206
if (res>PG_INT64_MAX||res<PG_INT64_MIN)
207+
{
208+
*result=0x5EED;/* to avoid spurious warnings */
183209
return true;
210+
}
184211
*result= (int64)res;
185212
return false;
186213
#else
187214
if ((a<0&&b>0&&a<PG_INT64_MIN+b)||
188215
(a>0&&b<0&&a>PG_INT64_MAX+b))
216+
{
217+
*result=0x5EED;/* to avoid spurious warnings */
189218
return true;
219+
}
190220
*result=a-b;
191221
return false;
192222
#endif
@@ -206,7 +236,10 @@ pg_mul_s64_overflow(int64 a, int64 b, int64 *result)
206236
int128res= (int128)a* (int128)b;
207237

208238
if (res>PG_INT64_MAX||res<PG_INT64_MIN)
239+
{
240+
*result=0x5EED;/* to avoid spurious warnings */
209241
return true;
242+
}
210243
*result= (int64)res;
211244
return false;
212245
#else
@@ -229,6 +262,7 @@ pg_mul_s64_overflow(int64 a, int64 b, int64 *result)
229262
(a<0&&b>0&&a<PG_INT64_MIN /b)||
230263
(a<0&&b<0&&a<PG_INT64_MAX /b)))
231264
{
265+
*result=0x5EED;/* to avoid spurious warnings */
232266
return true;
233267
}
234268
*result=a*b;

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