https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81065
Bug ID: 81065
Summary: UBSAN: false positive as a result of distribution
involving different types
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: sanitizer
Assignee: unassigned at gcc dot gnu.org
Reporter: babokin at gmail dot com
CC: dodji at gcc dot gnu.org, dvyukov at gcc dot gnu.org,
jakub at gcc dot gnu.org, kcc at gcc dot gnu.org, marxin at
gcc dot gnu.org
Target Milestone: ---
Similar to #80932, but note that x is unsigned char, it's essential.
> cat f.cpp
unsigned char x = 154;
int foo() {
// 8575 * (254408 - 9057) = 8575 * 245351 = 2103884825 = 0x7d66bc19
return 8575 * (1652 * x - 9057);
}
int main() {
foo();
return 0;
}
> g++ -fsanitize=undefined -O0 f.cpp -o out
> ./out
f.cpp:4:33: runtime error: signed integer overflow: 154 * 14165900 cannot be
represented in type 'int'
f.cpp:4:33: runtime error: signed integer overflow: -2113418696 + -77663775
cannot be represented in type 'int'
