$ cat oops.cpp
class refcounted
{
public:
refcounted() throw() : refcount(0) { }
unsigned add_reference() throw()
{
return ++refcount;
}
unsigned remove_reference() throw()
{
return --refcount;
}
unsigned get_refcount() const throw()
{
return refcount;
}
void set_refcount(unsigned r) throw()
{
refcount = r;
}
private:
unsigned refcount;
};
template <class T> class ptr
{
T* p;
public:
ptr(T* t) throw() : p(t)
{
p->set_refcount(1);
}
explicit ptr(T& t) throw() : p(&t)
{
p->add_reference();
}
ptr(const ptr& other) throw() : p(other.p)
{
p->add_reference();
}
~ptr()
{
if (p->remove_reference() == 0)
delete p;
}
ptr& operator=(const ptr& other)
{
T* otherp = other.p;
otherp->add_reference();
if (p->remove_reference() == 0)
delete p;
p = otherp;
return *this;
}
T& operator*() const throw()
{
return *p;
}
T* operator->() const throw()
{
return p;
}
friend inline T* get_pointer(const ptr& x) throw()
{
return x.p;
}
template <class U>
bool operator==(const ptr<U>& rhs) const throw()
{
return p == get_pointer(rhs);
}
};
class ex;
typedef const void* tinfo_t;
struct tinfo_static_t { };
enum status_flags {
dynallocated = 0x0001,
evaluated = 0x0002
};
class basic : public refcounted
{
public:
static const tinfo_static_t tinfo_static;
basic() : tinfo_key(&tinfo_static), flags(0) { }
basic(tinfo_t ti) : tinfo_key(ti), flags(0) { }
basic(const basic& other) : tinfo_key(other.tinfo_key),
flags(other.flags & ~dynallocated) { }
virtual basic* duplicate() const
{
return new basic(*this);
}
int compare(const basic& other) const
{
if (tinfo() == other.tinfo())
return compare_same_type(other);
else if (tinfo() < other.tinfo())
return -1;
else
return 1;
}
const basic& hold() const
{
flags |= evaluated;
return *this;
}
virtual ex eval(int level = 0) const;
tinfo_t tinfo() const
{
return tinfo_key;
}
virtual ~basic() { }
protected:
virtual int compare_same_type(const basic& other) const
{
if (this == &other)
return 0;
else if (this > &other)
return 1;
else
return -1;
}
tinfo_t tinfo_key;
mutable unsigned flags;
private:
friend class ex;
};
const tinfo_static_t basic::tinfo_static = { };
class ex {
private:
mutable ptr<basic> bp;
static ptr<basic> construct_from_basic(const basic& other)
{
if (!(other.flags & evaluated)) {
const ex& tmpex = other.eval(1);
if ((other.get_refcount() == 0) && (other.flags &
dynallocated))
delete &other;
return tmpex.bp;
} else {
if (other.flags & dynallocated) {
return ptr<basic>(const_cast<basic &>(other));
} else {
basic* bp = other.duplicate();
bp->flags |= dynallocated;
return bp;
}
}
}
public:
inline ex(const basic& other) : bp(construct_from_basic(other)) { }
ex eval(int level = 0) const
{
return bp->eval(level);
}
int compare(const ex& other) const
{
if (bp == other.bp)
return 0;
return bp->compare(*other.bp);
}
inline unsigned get_refcount() const
{
return bp->get_refcount();
}
};
ex basic::eval(int level) const
{
return hold();
}
class oops : public basic
{
int s;
protected:
virtual int compare_same_type(const basic& other) const
{
const oops& o = static_cast<const oops &>(other);
if (s == o.s)
return 0;
if (s > o.s)
return 1;
return -1;
}
public:
oops() : basic(&oops::tinfo_static), s(0) { }
oops(const int s_) : basic(&oops::tinfo_static), s(s_) { }
ex eval(int level) const
{
return oops(s).hold();
}
virtual oops* duplicate() const
{
return new oops(*this);
}
static const tinfo_static_t tinfo_static;
};
const tinfo_static_t oops::tinfo_static = { };
int main(int argc, char** argv)
{
int ret = 0;
const ex e = oops(1).hold();
const ex& f = argc > 1 ? e : e.eval(-2);
if (f.get_refcount() == 0)
++ret; // XXX: this should not happen
if (f.compare(e))
++ret; // XXX: this should not happen
return ret;
}
$ g++-4.3 -O0 -Wall -g oops.cpp -o /tmp/oops-4.3
$ /tmp/oops-4.3
Segmentation fault
When compiled with g++ 3.4, 4.{0,1,2} the program works as expected
(i.e. exits with zero status).
$ g++-4.3 -v -save-temps -O0 -Wall -g oops.cpp -o /tmp/oops-4.3
Using built-in specs.
Target: x86_64-linux-gnu
Configured with: ../src/configure linux gnu
Thread model: posix
gcc version 4.3.1 20080309 (prerelease) (Debian 4.3.0-1)
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-Wall' '-O0' '-g' '-o' '/tmp/oops-4.3'
'-shared-libgcc' '-mtune=generic'
/usr/lib/gcc/x86_64-linux-gnu/4.3.1/cc1plus -E -quiet -v -D_GNU_SOURCE
../oops.cpp -mtune=generic -Wall -fworking-directory -O0 -fpch-preprocess -o
oops.ii
ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"
ignoring nonexistent directory
"/usr/lib/gcc/x86_64-linux-gnu/4.3.1/../../../../x86_64-linux-gnu/include"
ignoring nonexistent directory "/usr/include/x86_64-linux-gnu"
#include "..." search starts here:
#include <...> search starts here:
/usr/include/c++/4.3
/usr/include/c++/4.3/x86_64-linux-gnu
/usr/include/c++/4.3/backward
/usr/local/include
/usr/lib/gcc/x86_64-linux-gnu/4.3.1/include
/usr/lib/gcc/x86_64-linux-gnu/4.3.1/include-fixed
/usr/include
End of search list.
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-Wall' '-O0' '-g' '-o' '/tmp/oops-4.3'
'-shared-libgcc' '-mtune=generic'
/usr/lib/gcc/x86_64-linux-gnu/4.3.1/cc1plus -fpreprocessed oops.ii -quiet
-dumpbase oops.cpp -mtune=generic -auxbase oops -g -O0 -Wall -version -o oops.s
GNU C++ (Debian 4.3.0-1) version 4.3.1 20080309 (prerelease) (x86_64-linux-gnu)
compiled by GNU C version 4.3.1 20080309 (prerelease), GMP version
4.2.2, MPFR version 2.3.1.
GGC heuristics: --param ggc-min-expand=63 --param ggc-min-heapsize=63134
Compiler executable checksum: 6b4f47123a81acc7bc0d52a2f374512f
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-Wall' '-O0' '-g' '-o' '/tmp/oops-4.3'
'-shared-libgcc' '-mtune=generic'
as -V -Qy -o oops.o oops.s
GNU assembler version 2.18.0 (x86_64-linux-gnu) using BFD version (GNU Binutils
for Debian) 2.18.0.20080103
COMPILER_PATH=/usr/lib/gcc/x86_64-linux-gnu/4.3.1/:/usr/lib/gcc/x86_64-linux-gnu/4.3.1/:/usr/lib/gcc/x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/4.3.1/:/usr/lib/gcc/x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/4.3.1/:/usr/lib/gcc/x86_64-linux-gnu/
LIBRARY_PATH=/usr/lib/gcc/x86_64-linux-gnu/4.3.1/:/usr/lib/gcc/x86_64-linux-gnu/4.3.1/:/usr/lib/gcc/x86_64-linux-gnu/4.3.1/../../../../lib/:/lib/../lib/:/usr/lib/../lib/:/usr/lib/gcc/x86_64-linux-gnu/4.3.1/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-Wall' '-O0' '-g' '-o' '/tmp/oops-4.3'
'-shared-libgcc' '-mtune=generic'
/usr/lib/gcc/x86_64-linux-gnu/4.3.1/collect2 --eh-frame-hdr -m elf_x86_64
--hash-style=both -dynamic-linker /lib64/ld-linux-x86-64.so.2 -o /tmp/oops-4.3
/usr/lib/gcc/x86_64-linux-gnu/4.3.1/../../../../lib/crt1.o
/usr/lib/gcc/x86_64-linux-gnu/4.3.1/../../../../lib/crti.o
/usr/lib/gcc/x86_64-linux-gnu/4.3.1/crtbegin.o
-L/usr/lib/gcc/x86_64-linux-gnu/4.3.1 -L/usr/lib/gcc/x86_64-linux-gnu/4.3.1
-L/usr/lib/gcc/x86_64-linux-gnu/4.3.1/../../../../lib -L/lib/../lib
-L/usr/lib/../lib -L/usr/lib/gcc/x86_64-linux-gnu/4.3.1/../../.. oops.o
-lstdc++ -lm -lgcc_s -lgcc -lc -lgcc_s -lgcc
/usr/lib/gcc/x86_64-linux-gnu/4.3.1/crtend.o
/usr/lib/gcc/x86_64-linux-gnu/4.3.1/../../../../lib/crtn.o
P.S.
I haven't posted the preprocessed source, since it's virtually identical
to the original one.
--
Summary: g++ 4.3.{0,1} miscompile this simple program
Product: gcc
Version: 4.3.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: varg at theor dot jinr dot ru
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35548
