Hello!
I had a C++ program that crashed, so I added debug output using clog.
Unfortunately the first out put to clog also crashed within iostreams.
I was able to make a test case that compiles fine with -Wall -Wextra, but
crashes:
---ugly code follows---
class d {
public:
static void f();
d() { f(); }
};
d dd;
#include <iostream>
using namespace std;
void d::f() { clog << "jdfdf" << endl; }
int main(int argc, char *argv[])
{
d::f();
}
---
If you #include <iostream> before the decalration of "dd", the program works;
if compiled as displayed, it crashes:
---
Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7b6f501 in std::ostream::sentry::sentry(std::ostream&) ()
from /usr/lib64/libstdc++.so.6
(gdb) bt
#0 0x00007ffff7b6f501 in std::ostream::sentry::sentry(std::ostream&) ()
from /usr/lib64/libstdc++.so.6
#1 0x00007ffff7b6fc19 in std::basic_ostream<char, std::char_traits<char> >&
std::__ostream_insert<char, std::char_traits<char> >(std::basic_ostream<char,
std::char_traits<char> >&, char const*, long) () from /usr/lib64/libstdc++.so.6
#2 0x00007ffff7b7001f in std::basic_ostream<char, std::char_traits<char> >&
std::operator<< <std::char_traits<char> >(std::basic_ostream<char,
std::char_traits<char> >&, char const*) () from /usr/lib64/libstdc++.so.6
#3 0x0000000000400942 in d::f () at t.cc:11
#4 0x0000000000400a6a in d::d (this=0x6011a0 <dd>) at t.cc:4
#5 0x00000000004009d9 in __static_initialization_and_destruction_0 (
__initialize_p=1, __priority=65535) at t.cc:7
#6 0x0000000000400a33 in global constructors keyed to dd() () at t.cc:15
#7 0x0000000000400b46 in __do_global_ctors_aux ()
#8 0x0000000000400783 in _init ()
#9 0x00007ffff72dcad8 in ?? () from /lib64/libc.so.6
#10 0x0000000000400ad5 in __libc_csu_init (argc=-7936,
argv=0x601080 <_ZSt4clog@@GLIBCXX_3.4>, envp=0x0) at elf-init.c:120
#11 0x00007ffff72ebbc2 in __libc_start_main () from /lib64/libc.so.6
#12 0x0000000000400859 in _start () at ../sysdeps/x86_64/elf/start.S:113
---
gcc is "gcc version 4.3.4 [gcc-4_3-branch revision 152973] (SUSE Linux" of
SLES11 SP3 (x86_64), but newer compilers react the same.
I guess the problem is that constructors are called sequentially without
dependency analysis. So if d() is acaaled before including iostream
(lexically), the program crashes.
Reagrds,
Ulrich Windl
P.S. Usually I don't write such ugly code
