I'm new to writing a pin tool to instrument the program.
Currently, I'm kind of stuck with printing out the program name (image? I would say) and the function that the instruction belongs to.
For example, I I have a program foo.cpp and function name func() that simple addition and cout.
Then, when I use a pin tool, I want to print like below
0xAddress foo (or lib64/ld-linux... etc) func disassembled_instruction (ex. move etc)
I can get the address and disassembled instructions, but not the program and function name.
Can anyone suggest me whether this is possible and how?
Thank you!
Program Name
To get the full path to the main binary (hence the program name) you must set an instrumentation routine for IMG (image) in your main() using IMG_AddInstrumentFunction.
In the analysis callback (passed to IMG_AddInstrumentFunction) use the IMG_IsMainExecutable function which simply returns a boolean indicating if the currently loaded image is the main binary (true) or not.
If the former function (IMG_IsMainExecutable) returns true you can call IMG_Name to get its full path.
For a full example see the Detecting the Loading and Unloading of Images (Image Instrumentation) example in the manual.
Function Name
Use PIN_InitSymbols in your main, before calling PIN_StartProgram.
You can instrument at the routine level using RTN_AddInstrumentFunction (or get the routine from the instruction, BBL or TRACE).
Once you have the RTN (routine), you can get its name with the RTN_Name function.
Check the manual for the example Procedure Instruction Count (Routine Instrumentation) which should give you a good start on how to use these functions.
Note: as obvious as its sounds, the target executable must have symbolic information (symbols): No symbols == no routine names.
You can use standard predefined macros for printing out the program and function name.
cout << __FILE__ << " " << __FUNCTION__ << endl;
I am making a small system and I want to be able to toggle "verbose" text output in the whole system.
I have made a file called globals.h:
namespace REBr{
extern bool console_verbose = false;
}
If this is true I want all my classes to print a message to the console when they are constructing, destructing, copying or doing pretty much anything.
For example:
window(string title="",int width=1280,int height=720):
Width(width),Height(height),title(title)
{
if(console_verbose){
std::cout<<"Generating window #"<<this->instanceCounter;
std::cout<<"-";
}
this->window=SDL_CreateWindow(title.c_str(),0,0,width,height,SDL_WINDOW_OPENGL);
if(console_verbose)
std::cout<<"-";
if(this->window)
{
this->glcontext = SDL_GL_CreateContext(window);
if(console_verbose)
std::cout<<".";
if(this->glcontext==NULL)
{
std::cout<<"FATAL ERROR IN REBr::WINDOW::CONSTR_OPENGLCONTEXT: "<<SDL_GetError()<<std::endl;
}
}
else std::cout<<"FATAL ERROR IN REBr::WINDOW::CONSTR_WINDOW: "<<SDL_GetError()<<std::endl;
if(console_verbose)
std::cout<<">done!"<<endl;
}
Now as you can see I have a lot of ifs in that constructor. And I REALLY dont want that since that will slow down my application. I need this to be as fast as possible without removing the "loading bar" (this helps me determine at which function the program stopped functioning).
What is the best/fastest way to accomplish this?
Everying in my system is under the namespace REBr
Some variants to achieve that:
Use some logger library. It is the best option as it gives you maximum flexibility and some useful experience ;) And you haven't to devise something. For example, look at Google GLOG.
Define some macro, allowing you to turn on/off all these logs by changing only the macro. But it isn't so easy to write such marco correctly.
Mark your conditional flag as constexpr. That way you may switch the flag and, depending on its value, compiler will optimise ifs in compiled program. But ifs will still be in code, so it looks kinda bulky.
Anyway, all these options require program recompilation. W/o recompilation it is impossible to achieve the maximum speed.
I often use a Logger class that supports debug levels. A call might look like:
logger->Log(debugLevel, "%s %s %d %d", timestamp, msg, value1, value2);
The Logger class supports multiple debug levels so that I can fine tune the debug output. This can be set at any time through the command line or with a debugger. The Log statement uses a variable length argument list much like printf.
Google's logging module is widely used in the industry and supports logging levels that you can set from the command line. For example (taken from their documentation)
VLOG(1) << "I'm printed when you run the program with --v=1 or higher";
VLOG(2) << "I'm printed when you run the program with --v=2 or higher";
You can find the code here https://github.com/google/glog and the documentation in the doc/ folder.
I'm using the google logger (glog) in a C++ project, where source code contains printout of informational items and progress:
std::cout << some_useful_stuff << "\n";
And I can use GLOG to log informational items:
LOG(INFO) << some_useful_stuff << "\n"; \\ gets echoed to stdout
I can't change all the std::cout statements throughout the codebase (as I'm using some subrepos from third parties etc, and unable to add my own logging statements to them), this prevents me from using an if-else construct (which would be ugly anyway, wrapping every single output statement in logic).
So how could I replicate stdout outputs to GLog?
std::cout << some_useful_stuff << "\n"; \\ message also goes to LOG(INFO)
Possibly useful: I actually don't need this to happen at the same time; it's useful to have a choice like {CONSOLE, LOGS, BOTH} but I could put up with the simpler choice between {CONSOLE, LOGS}.
Also - experienced programmer but C++ newbie so if this is mega simple; apologies - and thanks in advance!
Not sure about glog, but usually we use dup2 system call to redirect output of one file handler to another.
For e.g. in your case to make all std::cout write to the log file used by glog just do
dup2(glog_file_handler,stdout);
This would work if you can some how get filehandle of the log file that glog is writing to. Refer http://man7.org/linux/man-pages/man2/dup.2.html for more details.
Hope this helps.
P.S. This won't work if your program has multiple threads/procesess writing to same glog file and if glog does synchronized writes to log file
I am working with Perl embedded in our application. We have installed quite a few C++ functions that are called from within Perl. One of them is a logging function. I would like to add the file name and line number of the Perl file that called this function to the log message.
I know on the Perl side I can use the "caller()" function to get this information, but this function is already used in hundreds of locations, so I would prefer to modify the C++ side, is this information passed to the C++ XSUB functions and if so how would I get at it?
Thanks.
This should work:
char *file;
I32 line;
file = OutCopFILE(PL_curcop);
line = CopLINE(PL_curcop);
Control ops (cops) are one of the two ops OP_NEXTSTATE and op_DBSTATE,
that (loosely speaking) are separate statements.
They hold information important for lexical state and error reporting.
At run time, PL_curcop is set to point to the most recently executed cop,
and thus can be used to determine our current state.
— cop.h
Can't you call perl builtins from XS? I confess I don't know.
If not, you could always do something like this:
sub logger { _real_logger(caller, #_) }
assuming logger is what your function is called (and you rename your C++ XS function to _real_logger. You could also do this, presumably, if you need to hide yourself in the call tree:
sub logger {
unshift #_, caller;
goto &_real_logger;
}
which is of course the normal form of goto used in AUTOLOAD.
These will add overhead, of course, but probably not a big deal for a logging function.
I've been wondering, what is the point of clog? As near as I can tell, clog is the same as cerr but with buffering so it is more efficient. Usually stderr is the same as stdout, so clog is the same as cout. This seems pretty lame to me, so I figure I must be misunderstanding it. If I have log messages going out to the same place I have error messages going out to (perhaps something in /var/log/messages), then I probably am not writing too much out (so there isn't much lost by using non-buffered cerr). In my experience, I want my log messages up to date (not buffered) so I can help find a crash (so I don't want to be using the buffered clog). Apparently I should always be using cerr.
I'd like to be able to redirect clog inside my program. It would be useful to redirect cerr so that when I call a library routine I can control where cerr and clog go to. Can some compilers support this? I just checked DJGPP and stdout is defined as the address of a FILE struct, so it is illegal to do something like "stdout = freopen(...)".
Is it possible to redirect clog, cerr, cout, stdin, stdout, and/or stderr?
Is the only difference between clog and cerr the buffering?
How should I implement (or find) a more robust logging facility (links please)?
Is it possible to redirect clog, cerr, cout, stdin, stdout, and/or stderr?
Yes. You want the rdbuf function.
ofstream ofs("logfile");
cout.rdbuf(ofs.rdbuf());
cout << "Goes to file." << endl;
Is the only difference between clog and cerr the buffering?
As far as I know, yes.
If you're in a posix shell environment (I'm really thinking of bash), you can redirect any
file descriptor to any other file descriptor, so to redirect, you can just:
$ myprogram 2>&5
to redirect stderr to the file represented by fd=5.
Edit: on second thought, I like #Konrad Rudolph's answer about redirection better. rdbuf() is a more coherent and portable way to do it.
As for logging, well...I start with the Boost library for all things C++ that isn't in the std library. Behold: Boost Logging v2
Edit: Boost Logging is not part of the Boost Libraries; it has been reviewed, but not accepted.
Edit: 2 years later, back in May 2010, Boost did accept a logging library, now called Boost.Log.
Of course, there are alternatives:
Log4Cpp (a log4j-style API for C++)
Log4Cxx (Apache-sponsored log4j-style API)
Pantheios (defunct? last time I tried I couldn't get it to build on a recent compiler)
Google's GLog (hat-tip #SuperElectric)
There's also the Windows Event logger.
And a couple of articles that may be of use:
Logging in C++ (Dr. Dobbs)
Logging and Tracing Simplified (Sun)
Since there are several answers here about redirection, I will add this nice gem I stumbled across recently about redirection:
#include <fstream>
#include <iostream>
class redirecter
{
public:
redirecter(std::ostream & dst, std::ostream & src)
: src(src), sbuf(src.rdbuf(dst.rdbuf())) {}
~redirecter() { src.rdbuf(sbuf); }
private:
std::ostream & src;
std::streambuf * const sbuf;
};
void hello_world()
{
std::cout << "Hello, world!\n";
}
int main()
{
std::ofstream log("hello-world.log");
redirecter redirect(log, std::cout);
hello_world();
return 0;
}
It's basically a redirection class that allows you to redirect any two streams, and restore it when you're finished.
Redirections
Konrad Rudolph answer is good in regard to how to redirect the std::clog (std::wclog).
Other answers tell you about various possibilities such as using a command line redirect such as 2>output.log. With Unix you can also create a file and add another output to your commands with something like 3>output.log. In your program you then have to use fd number 3 to print the logs. You can continue to print to stdout and stderr normally. The Visual Studio IDE has a similar feature with their CDebug command, which sends its output to the IDE output window.
stderr is the same as stdout?
This is generally true, but under Unix you can setup the stderr to /dev/console which means that it goes to another tty (a.k.a. terminal). It's rarely used these days. I had it that way on IRIX. I would open a separate X-Window and see errors in it.
Also many people send error messages to /dev/null. On the command line you write:
command ...args... 2>/dev/null
syslog
One thing not mentioned, under Unix, you also have syslog().
The newest versions under Linux (and probably Mac OS/X) does a lot more than it used to. Especially, it can use the identity and some other parameters to redirect the logs to a specific file (i.e. mail.log). The syslog mechanism can be used between computers, so logs from computer A can be sent to computer B. And of course you can filter logs in various ways, especially by severity.
The syslog() is also very simple to use:
syslog(LOG_ERR, "message #%d", count++);
It offers 8 levels (or severity), a format a la printf(), and a list of arguments for the format.
Programmatically, you may tweak a few things if you first call the openlog() function. You must call it before your first call to syslog().
As mentioned by unixman83, you may want to use a macro instead. That way you can include some parameters to your messages without having to repeat them over and over again. Maybe something like this (see Variadic Macro):
// (not tested... requires msg to be a string literal)
#define LOG(lvl, msg, ...) \
syslog(lvl, msg " (in " __FILE__ ":%d)", __VA_ARGS__, __LINE__)
You may also find __func__ useful.
The redirection, filtering, etc. is done by creating configuration files. Here is an example from my snapwebsites project:
mail.err /var/log/mail/mail.err
mail.* /var/log/mail/mail.log
& stop
I install the file under /etc/rsyslog.d/ and run:
invoke-rc.d rsyslog restart
so the syslog server handles that change and saves any mail related logs to those folders.
Note: I also have to create the /var/log/mail folder and the files inside the folder to make sure it all works right (because otherwise the mail daemon may not have enough permissions.)
snaplogger (a little plug)
I've used log4cplus, which, since version 1.2.x, is quite good. I have three cons about it, though:
it requires me to completely clear everything if I want to call fork(); somehow it does not survive a fork(); call properly... (at least in the version I had it used a thread)
the configuration files (.properties) are not easy to manage in my environment where I like the administrators to make changes without modifying the original
it uses C++03 and we are now in 2019... I'd like to have at least C++11
Because of that, and especially because of point (1), I wrote my own version called snaplogger. This is not exactly a standalone project, though. I use many other projects from the snapcpp environment (it's much easier to just get snapcpp and run the bin/build-snap script or just get the binaries from launchpad.)
The advantage of using a logger such as snaplogger or log4cplus is that you generally can define any number of destinations and many other parameters (such as the severity level as offered by syslog()). The log4cplus is capable of sending its output to many different places: files, syslog, MS-Windows log system, console, a server, etc. Check out the appenders in those two projects to have an idea of the list of possibilities. The interesting factor here is that any log can be sent to all the destinations. This is useful to have a file named all.log where all your services send their logs. This allows to understand certain bugs which would not be as easy with separate log files when running many services in parallel.
Here is a simple example in a snaplogger configuration file:
[all]
type=file
lock=true
filename=/var/log/snapwebsites/all.log
[file]
lock=false
filename=/var/log/snapwebsites/firewall.log
Notice that for the all.log file I require a lock so multiple writers do not mangle the logs between each others. It's not necessary for the [file] section because I only have one process (no threads) for that one.
Both offer you a way to add your own appenders. So for example if you have a Qt application with an output window, you could write an appender to send the output of the SNAP_LOG_ERROR() calls to that window.
snaplogger also offers you a way to extend the variable support in messages (also called the format.) For example, I can insert the date using the ${date} variable. Then I can tweak it with a parameter. To only output the year, I use ${date:year}. This variable parameter support is also extensible.
snaplogger can filter the output by severity (like syslog), by a regex, and by component. We have a normal and a secure component, the default is normal. I want logs sent to the secure component to be written to secure files. This means in a sub-directory which is way more protected than the normal logs that most admins can review. When I run my HTTP services, some times I send information such as the last 3 digits of a credit card. I prefer to have those in a secure log. It could also be password related errors. Anything I deem to be a security risk in a log, really. Again, components are extensible so you can have your own.
One little point about the redirecter class. It needs to be destroyed properly, and only once. The destructor will ensure this will happen if the function it is declared in actually returns, and the object itself is never copied.
To ensure it can't be copied, provide private copy and assignment operators:
class redirecter
{
public:
redirecter(std::ostream & src, std::ostream & dst)
: src_(src), sbuf(src.rdbuf(dst.rdbuf())) {}
~redirecter() { src.rdbuf(sbuf); }
private:
std::ostream & src_;
std::streambuf * const sbuf_;
// Prevent copying.
redirecter( const redirecter& );
redirecter& operator=( const redirecter& );
};
I'm using this technique by redirecting std::clog to a log file in my main(). To ensure that main() actually returns, I place the guts of main() in a try/catch block. Then elsewhere in my program, where I might call exit(), I throw an exception instead. This returns control to main() which can then execute a return statement.
Basic Logger
#define myerr(e) {CriticalSectionLocker crit; std::cerr << e << std::endl;}
Used as myerr("ERR: " << message); or myerr("WARN: " << message << code << etc);
Is very effective.
Then do:
./programname.exe 2> ./stderr.log
perl parsestderr.pl stderr.log
or just parse stderr.log by hand
I admit this is not for extremely performance critical code. But who writes that anyway.