I'm trying to find out what part of a program prints to stdout.
I can set a breakpoint using command like:
b std::ostream::operator<<(int)
but when i type: b std::operator<<(std::ostream&, const std::string&) no breakpoint is created.
So there are two questions:
How to set a breakpoint on operator << (..., cosnt std::string&) ?
I want to set a breakpoint, but i don't know the exact name of the function. How to search for a function using regexp or part of its name ?
Use "info functions <<.*string" to search for functions with << and string in their names. info functions takes a regular expression as argument.
Then select from the listed functions the one you want. Remove the ; at the end of the declaration if any and paste the declaration as an argument to the break command:
$ gdb -q ./ostream-operator-breakpoint
<...>
(gdb) start
Temporary breakpoint 1 at 0x4006b0: file ostream-operator-breakpoint.cc, line 4.
Starting program: /home/scottt/Dropbox/stackoverflow/ostream-operator-breakpoint
<...>
(gdb) info functions <<.*string
All functions matching regular expression "<<.*string":
File /usr/src/debug/gcc-4.7.2-20121109/obj-x86_64-redhat-linux/x86_64-redhat-linux/libstdc++-v3/include/bits/basic_string.h:
std::basic_ostream<char, std::char_traits<char> > &std::operator<< <char, std::char_traits<char>, std::allocator<char> >(std::basic_ostream<char, std::char_traits<char> >&, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&);
std::basic_ostream<wchar_t, std::char_traits<wchar_t> > &std::operator<< <wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >(std::basic_ostream<wchar_t, std::char_traits<wchar_t> >&, std::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> > const&);
(gdb) break std::basic_ostream<char, std::char_traits<char> > &std::operator<< <char, std::char_traits<char>, std::allocator<char> >(std::basic_ostream<char, std::char_traits<char> >&, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)
Breakpoint 2 at 0x3cbfa94640: file /usr/src/debug/gcc-4.7.2-20121109/obj-x86_64-redhat-linux/x86_64-redhat-linux/libstdc++-v3/include/bits/basic_string.h, line 2750.
The start (or run) command is required for dynamically linked programs. Unless you first start the inferior process, info functions wouldn't list functions from shared libraries such as libstdc++.
Related
So everything was working great until I decided to comment out a print method (for debugging). Once I commented it out, my code began to seg fault.
I assumed this was because I was somehow modifying something in my print method, so I commented out one line at a time so I could find where it was happening. After commenting every single line in the print out, I noticed it would seg fault only when I wasn't calling the print method (even if it was completely empty!).
So I did this:
void emptyMethod(Qclass c) {}
void Typechecker::initializeClasses(AST::Node *astRoot) {
...
Qclass clazz;
...
this->classes[clazz.name] = clazz;
emptyMethod(clazz); // I have no idea why I have to do this, but it
seg faults if I don't
...
}
This fixes my seg fault.
Structs in question:
struct Qclass; // forward declare
struct Qmethod {
AST::Node *node; // pointer to the node in the tree
// The reference to the containing class of a method is a pointer because
// it may not be fully initialized when passed into any given Qmethod.
// This is okay because we don't use *clazz until after all initialization is
complete.
Qclass *clazz;
std::string name;
std::vector<std::string> init;
std::map<std::string, std::string> type;
std::vector<AST::Node*> stmts;
};
struct Qclass {
AST::Node *node; // pointer to the node in the tree
std::string name;
std::string super;
Qmethod constructor;
std::vector<Qmethod> methods;
// for use in init before use checking in non constructor methods
std::vector<std::string> instanceVars;
};
Where it is seg faulting:
bool Typechecker::initCheckStmt(Qmethod &method, AST::Node *stmt, bool isConstructor) {
...
method.clazz->instanceVars.push_back(left->get(IDENT)->name); // seg faults here when not calling the empty method
...
return true;
}
Seg fault error:
#0 0x00007fffff1919b8 in std::__cxx11::basic_string<char,
std::char_traits<char>, std::allocator<char>
>::basic_string(std::__cxx11::basic_string<char, std::char_traits<char>,
std::allocator<char> > const&) () from /usr/lib/x86_64-linux-
gnu/libstdc++.so.6
#1 0x000000000041ab38 in void __gnu_cxx::new_allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >::construct<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&>(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) ()
#2 0x0000000000417dc6 in void std::allocator_traits<std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > >::construct<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&>(std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) ()
#3 0x0000000000415b56 in std::vector<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > >::push_back(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) ()
#4 0x00000000004136b3 in Typechecker::initCheckStmt(Qmethod&, AST::Node*, bool) ()
#5 0x00000000004134b9 in Typechecker::getLeaves(Qmethod&, AST::Node*, std::vector<AST::Node*, std::allocator<AST::Node*> >&, bool) ()
#6 0x00000000004137c8 in Typechecker::initCheckQmethod(Qmethod&, bool) ()
#7 0x0000000000413a16 in Typechecker::initializeBeforeUseCheck() ()
#8 0x0000000000413d12 in Typechecker::checkProgram() ()
#9 0x0000000000426e7b in main ()
I can see it must have something to do with the instanceVars vector, but I don't understand why an empty method call would fix it. My Googling ability isn't helping me at all, so any pointers would be very much appreciated.
(this code is for a compilers course)
You've got yourself some undefined behavior. Your program is doing something—maybe an out-of-bounds memory access, who knows—that is throwing off your program. In C++, when your program does that, all bets are off for what it does next, including segfaulting.
That empty method call is hiding the bug, but it's not fixing the bug. As you correctly noted, that method call shouldn't affect whether it segfaults. The reason why it does is because of the undefined behavior.
To solvev this, you'll need to look at the rest of your program to determine where there might be an issue. Just the one line where it broke isn't enough; you should look before and after the line where it ends up segfaulting, as well as what you're passing into initializeClasses.
My app is using boost::program_options and it's triggering an AddressSanitizer "stack-buffer-overflow" while generating an error message from an exception.
I'm not worried about the boost bug - the functionality works and this is just in the command line parsing portion of a non-production app. However I'd like to suppress the AddressSanitizer message.
ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7fffe6ce7070 at pc 0x0000007406cd bp 0x7fffe6ce6fe0 sp 0x7fffe6ce6fd8
READ of size 8 at 0x7fffe6ce7070 thread T0
#0 0x7406cc in std::_Head_base<0ul, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >&&, false>::_M_head(std::_Head_base<0ul, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >&&, false>&) /frc/toolchain6/include/c++/5.3.0/tuple:142
#1 0x7406cc in _M_create_node /frc/toolchain6/include/c++/5.3.0/tuple:347
#2 0x7403fd in std::_Rb_tree_iterator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > > std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::_Select1st<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >::_M_emplace_hint_unique<std::piecewise_construct_t const&, std::tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >&&>, std::tuple<> >(std::_Rb_tree_const_iterator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > >, std::piecewise_construct_t const&, std::tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >&&>&&, std::tuple<>&&) /frc/toolchain6/include/c++/5.3.0/bits/stl_tree.h:2170
#3 0xd5eff8 in boost::program_options::error_with_option_name::substitute_placeholders(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) const (/home/joe/myapp_workspace/myapp/myapp-debug+0xd5eff8)
#4 0xd5c0dd in boost::program_options::error_with_option_name::what() const (/home/joe/myapp_workspace/myapp/myapp-debug+0xd5c0dd)
#5 0x58addf in main /home/joe/myapp_workspace/myapp/main.cpp:62
#6 0x7fd7e056176c in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2176c)
#7 0x436aa0 (/home/joe/myapp_workspace/myapp/myapp-debug+0x436aa0)
I've tried using the ASAN_OPTIONS suppression file method but that only seems to support a very short list of error types (such as "vptr_check" and "leak").
I don't think there's an easy way to suppress this error - Clang version of Asan has blacklisting mechanism but it's context insensitive so you'd have to disable memory checking in all usages of std::string which is highly undesirable.
One option is to use -fsanitize-recover=address compiler flag and add halt_on_error=0 to your ASAN_OPTIONS environment variable (see wiki for details and note that recovery is only supported is relatively new GCC and Clang). This will continue execution after first error. You'll then be able to examine full Asan report and select what interests you.
I am learning debugging with GDB and I am not sure what to do.
I run a program inside GDB, that I need to get working, and it crashes with SEGFAULT. When I do backtrace inside GDB, I see this.
(gdb) backtrace
#0 0x08200100 in boost::shared_ptr<boost::re_detail::basic_regex_implementation<char, boost::regex_traits<char, boost::cpp_regex_traits<char> > > >::get (this=0x2) at /usr/include/boost/smart_ptr/shared_ptr.hpp:668
#1 0x081f94c3 in boost::basic_regex<char, boost::regex_traits<char, boost::cpp_regex_traits<char> > >::get_traits (this=0x2) at /usr/include/boost/regex/v4/basic_regex.hpp:619
#2 0x081ef769 in boost::re_detail::perl_matcher<__gnu_cxx::__normal_iterator<char const*, std::string>, std::allocator<boost::sub_match<__gnu_cxx::__normal_iterator<char const*, std::string> > >, boost::regex_traits<char, boost::cpp_regex_traits<char> > >::perl_matcher (this=0xb60d3eb4, first=..., end=..., what=..., e=...,
f=boost::regex_constants::match_any, l_base=...) at /usr/include/boost/regex/v4/perl_matcher.hpp:372
#3 0x081e2214 in boost::regex_match<__gnu_cxx::__normal_iterator<char const*, std::string>, std::allocator<boost::sub_match<__gnu_cxx::__normal_iterator<char const*, std::string> > >, char, boost::regex_traits<char, boost::cpp_regex_traits<char> > > (first=..., last=..., m=..., e=..., flags=boost::regex_constants::match_any)
at /usr/include/boost/regex/v4/regex_match.hpp:49
#4 0x081d43bf in boost::regex_match<std::char_traits<char>, std::allocator<char>, char, boost::regex_traits<char, boost::cpp_regex_traits<char> > > (s=..., e=..., flags=boost::regex_constants::match_default)
at /usr/include/boost/regex/v4/regex_match.hpp:100
#5 0x081ca3c1 in [my project] (this=0x2, request=0xb5706630)
at [source of my project]:127
[more calls here]
Now I want to examine what was inside request at #5, on the line 127. Request is a C-style pointer to C++ object of class request_data, which is defined in my project. The definition of my function is bool match_request(request_data *request) const.
What should I write in gdb to actually get to the content of request as it was before the program segfaulted?
Well, your this pointer at #5 does not look too healthy, but aside from that, I think you need a GDB tutorial:
How to change stack frames
How to examine variables
This does it.
(gdb) frame 5
(gdb) print *request
I have a project I am working on where I have some strange behavior with the std maps.
I had my own typedef map defined which mapped strings to a pointer of a custom type. The application crashed anytime that I excess the map after I add the first pair to the map.
After a lot of messing around I changed the map to a and moved it to the first call in my application and it still crashes. I have no idea what could be going on. Any help would be appreciated.
Here is the code that crashes at the moment.
LoggerPtr syslogger(Logger::getLogger("CISInterface"));
int main(int argc, char *argv[])
{
typedef std::map<string, string> MyMapDef;
MyMapDef tmpString;
tmpString.insert(MyMapDef::value_type("0000", "d"));
tmpString.insert(MyMapDef::value_type("1111", "d")); //Crashes here.
tmpString.insert(MyMapDef::value_type("2222", "d"));
// std::string configFile;
// int c;
// if(argc < 2)
// {
// //Must have c option
// std::cout << "Usage -c configFileName" << std::endl;
// exit(EXIT_FAILURE);
// }
//Rest of main commented out.
...
And here is the stack trace -
CISInterface Debug [C/C++ Application]
gdb/mi (10/31/12 6:02 PM) (Suspended)
Thread [1] (Suspended: Signal 'SIGSEGV' received. Description: Segmentation fault.)
6 std::basic_string<char, std::char_traits<char>, std::allocator<char> >::compare(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) const() 0x00000032fd49c416
5 std::operator< <char, std::char_traits<char>, std::allocator<char> >() basic_string.h:2317 0x0000000000417ec7
4 std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >::operator() stl_function.h:230 0x000000000041706f
3 std::_Rb_tree<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> > const, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::_Select1st<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> > const, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> > const, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >::_M_insert_unique() stl_tree.h:1170 0x0000000000415d00
2 std::map<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> > const, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >::insert() stl_map.h:500 0x00000000004150eb
1 main() CISInterface.cpp:29 0x000000000041916d
gdb (10/31/12 6:02 PM)
/home/cillian/workspace/CISInterface/Debug/CISInterface (10/31/12 6:02 PM)
What other areas should I be looking at that could be causing problems. Could it be in the libraries that I'm linking with? I have created a second project with just these lines of code that links with the same libraries (but doesn't have any code that calls into them.) and it doesn't crash.
Problem solved.
Thought I'd add it here on the off chance anyone else ever does the same thing.
I slowly removed files in my project to try and find the offending file. I was thinking that it must be something defined in a header file that was causing issues (like a static). It took a long time but I think I've found it. I had a header file that defines a number of structs. These are serialized to the wire so I had them 1 byte aligned using #pragma pack (push) which I put at the top of the file and #pragma pack (pop) at the bottom. But I then added a couple of #include statements after the first #pragma definition meaning that these includes were aligned incorrectly and caused some nondeterministic behavior. Thanks everyone that had a look. Should probably use the attribute syntax and I wouldn't had the problem. Offending code is below for completeness.
#pragma pack (push)
#pragma pack (1)
#include <string> //Wrong place for includes!
#include <Units.h>
typedef struct
{
....
}
#pragma pack (pop)
Thanks to everyone who had a look at initial problem.
In my development environment, I'm compiling a code base using GNU C++ 3.4.6. Code is under development, and unfortunately crashes now and then. It's nice to be able to run the traceback through a demangler, and I use c++filt 3.4. The problem comes when functions have a number of STL parameters. Consider
My_callback::operator()(
Status&,
std::set<std::string> const&,
std::vector<My_parameter*> const&,
My_attribute_set const&,
std::vector<My_parameter_base*> const&,
std::vector<My_parameter> const&,
std::set<std::string> const&
)
{
// ...
}
When this function is in the traceback, the mangled output on my platform is:
(_ZN30My_callbackclER11StatusRKSt3setISsSt4lessISsESaISsEERKSt6vectorIP13My_parameterSaISB_EERK17My_attribute_setRKS9_IP18My_parameter_baseSaISK_EERKS9_ISA_SaISA_EES8_+0x76a) [0x13ffdaa]
c++filt kindly demangles it to
(My_callback::operator()(Status&, std::set<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > const&, std::vector<My_parameter*, std::allocator<My_parameter*> > const&, My_attribute_set const&, std::vector<My_parameter_base*, std::allocator<My_parameter_base*> > const&, std::vector<My_parameter, std::allocator<My_parameter> > const&, std::set<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > const&)+0x76a) [0x13ffdaa]
This is the same problem as compiler errors encountered when using templates. However, the STL is a fairly regular and recognizable package of templates. So what I'm hoping is that someone out there has created an enhanced version of c++filt which would dump something closer to the original function signature. Any hints?
STLFilt simplifies and/or reformats long-winded C++ error and warning messages, with a focus on STL-related diagnostics. The result renders many of even the most cryptic diagnostics comprehensible.