https://bugs.llvm.org/show_bug.cgi?id=46124
Bug ID: 46124
Summary: Clang stop detecting UBs after a divide by zero
Product: clang
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: enhancement
Priority: P
Component: C++
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected],
[email protected], [email protected],
[email protected]
This code test1.cc
#include<iostream>
int main () {
int a = 1;
for (int i = 0; i < 10; ++i) {
a /= i; // Error: division by zero on the first iteration
}
int b = 0;
int bb = 0 / b;
0 / 0;
std::cout << "ok" << std::endl;
return 0;
}
$clang++-trunk -w -fsanitize=integer-divide-by-zero test1.cc ; ./a.out
test1.cc:5:11: runtime error: division by zero
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior example.cpp:5:11 in
UndefinedBehaviorSanitizer:DEADLYSIGNAL
==1==ERROR: UndefinedBehaviorSanitizer: FPE on unknown address 0x000000431817
(pc 0x000000431817 bp 0x7fff88ddde50 sp 0x7fff88ddde20 T1)
#0 0x431817 (/app/output.s+0x431817)
#1 0x7f56e7e59b96 (/lib/x86_64-linux-gnu/libc.so.6+0x21b96)
#2 0x4031e9 (/app/output.s+0x4031e9)
UndefinedBehaviorSanitizer can not provide additional info.
SUMMARY: UndefinedBehaviorSanitizer: FPE (/app/output.s+0x431817)
==1==ABORTING
Clang only detects one runtime error in for statement but leaves out detecting
the statements following ones.
In test2.cc
#include<iostream>
int main () {
/*
int a = 1;
for (int i = 0; i < 10; ++i) {
a /= i; // Error: division by zero on the first iteration
}
*/
int b = 0;
int bb = 0 / b;
0 / 0;
std::cout << "ok" << std::endl;
return 0;
}
$clang++-trunk -fsanitize=integer-divide-by-zero test2.cc ; ./a.out
test2.cc:11:16: runtime error: division by zero
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior example.cpp:11:16 in
UndefinedBehaviorSanitizer:DEADLYSIGNAL
==1==ERROR: UndefinedBehaviorSanitizer: FPE on unknown address 0x0000004317fd
(pc 0x0000004317fd bp 0x7ffd6c2922f0 sp 0x7ffd6c2922d0 T1)
#0 0x4317fd (/app/output.s+0x4317fd)
#1 0x7fe566be1b96 (/lib/x86_64-linux-gnu/libc.so.6+0x21b96)
#2 0x4031e9 (/app/output.s+0x4031e9)
UndefinedBehaviorSanitizer can not provide additional info.
SUMMARY: UndefinedBehaviorSanitizer: FPE (/app/output.s+0x4317fd)
==1==ABORTING
In gcc-trunk
$./g++ -w -fsanitize=integer-divide-by-zero test2.cc ; ./a.out
test.cc:11:16: runtime error: division by zero
test.cc:12:7: runtime error: division by zero
ok
Should the main function return from "return 0" rather than exit directly from
the for statement?
I also file a bug report in GCC, they confirmed this limitation immediately.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95385
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