https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66411
Bug ID: 66411
Summary: False positive in array bound check in a for loop
Product: gcc
Version: 4.9.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: dougkwan at google dot com
Target Milestone: ---
gcc-4.9.2 produces a bogus out of bound warning for the following test case
----
class A;
class C {
void m_fn1();
A *a_;
};
class A {
public:
void m_fn2();
int elements_[8];
int num_elements_;
};
int a;
void A::m_fn2() {
int b = 0;
if (num_elements_)
++b;
for (int i = b + 1; i < num_elements_; ++i) {
if (elements_[i])
++a;
}
}
void C::m_fn1() {
a_->m_fn2();
}
----
sh-4.3$ ~/gcc-4.9.2/install/bin/g++ -O3 -Werror=array-bounds bug.cc -c -o
/dev/null
bug.cc: In member function ‘void A::m_fn2()’:
bug.cc:21:20: error: array subscript is above array bounds
[-Werror=array-bounds]
if (elements_[i])
^
bug.cc: In member function ‘void C::m_fn1()’:
bug.cc:21:20: error: array subscript is above array bounds
[-Werror=array-bounds]
if (elements_[i])
^
cc1plus: some warnings being treated as errors
sh-4.3$
gcc config:
sh-4.3$ ~/gcc-4.9.2/install/bin/g++ -v
Using built-in specs.
COLLECT_GCC=/usr/local/google/home/dougkwan/gcc-4.9.2/install/bin/g++
COLLECT_LTO_WRAPPER=/usr/local/google/home/dougkwan/gcc-4.9.2/install/bin/../libexec/gcc/x86_64-unknown-linux-gnu/4.9.2/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-4.9.2/configure --enable-languages=c,c++
--disable-bootstrap --disable-multilib
Thread model: posix
gcc version 4.9.2 (GCC)
