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Full Discussion: to convert int to hex
Top Forums Programming to convert int to hex Post 302152328 by DreamWarrior on Wednesday 19th of December 2007 03:35:19 PM
Old 12-19-2007
Quote:
Originally Posted by WebKruncher
#include <string>
#include <sstream>
using namespace std;

//This spends some extra cycles, offers simplicity, elegance and safety.
string IntToHexString(int i)
{
stringstream ss;
ss<<"0x"<<hex<<i;
string retval; retval=ss.str().c_str();
return retval;
}


//usage
cout<<"Hex for 32 is "<<IntToHexString(32)<<endl;
// as always handle your seh exceptions with a try / catch.
Correct me if I am wrong, but it also either 1) leaks memory, 2) reads a wild pointer, or 3) is thread unsafe:

Logically:

The .c_str call must return a "string".

Given:

A string is a pointer to a "NULL terminated string."

A "NULL terminated string" is a sequence of characters terminated by a '\0' character; we shall call this a "buffer".

A buffer resides somewhere in memory.

Therefore:

The .c_str call must return a pointer a buffer containing its contents.

In order not to leak, the above buffer must be freed at some point. To be freed the buffer must still referenced. Since the caller of IntToHexString does not take a reference then to not leak, either a) someone else must free it or b) someone else has a reference to it.

If (a) then the "somewhere" else may be the destructor of stringstream class. I presume this destructor is called when the stack for your function is cleaned up. This means that the string returned by IntToHexString becomes "wild" as soon as it returns.

If (b) then the buffer can be overwritten at some point by the class still holding a reference to it and therefore can not be thread safe.

If neither a nor b occurs then the code leaks. The only way this is untrue is if the compiler takes care of destroying the string returned by IntToHexString.
 

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LEARN ABOUT DEBIAN

shevek_process

shevek::process(3)					     Library Functions Manual						shevek::process(3)

NAME

       shevek::process -

       Create a process, optionally connection its standard in- and output streams to the calling program.

SYNOPSIS

       #include <process.hh>

       Inherits shevek::refbase.

   Public Member Functions
       Glib::RefPtr< shevek::fd > in ()
	   The standard input pipe, if it was requested.
       Glib::RefPtr< shevek::fd > out ()
	   The standard output pipe, if it was requested.
       Glib::RefPtr< shevek::fd > err ()
	   The standard error pipe, if it was requested.
       pid_t pid ()
	   The process ID.
       ~process ()
	   The destructor. This kills the process if it was still running.

   Static Public Member Functions
       static Glib::RefPtr< process > create (std::string const &command, std::list< std::string > &argv, bool pipe_stdin=true, bool
	   pipe_stdout=true, bool pipe_stderr=true)
	   Create a process from a filename and an argument list.
       static Glib::RefPtr< process > create (std::string const &command, std::list< std::string > &argv, std::list< std::string > const &envp,
	   bool pipe_stdin=true, bool pipe_stdout=true, bool pipe_stderr=true)
	   Create a process from a filename, an argument list and an environment.
       static Glib::RefPtr< process > shell (std::string const &command, bool pipe_stdin=true, bool pipe_stdout=true, bool pipe_stderr=true,
	   std::string const &sh='/bin/sh')
	   Run a string with the shell.
       static std::string run (std::string const &command, std::string const &sh)
	   Run a process and return its output.
       static Glib::RefPtr< process > create (std::string const &command, bool pipe_stdin=true, bool pipe_stdout=true, bool pipe_stderr=true)
	   Create a process without arguments.
       static Glib::RefPtr< process > create (std::string const &command, std::string const &a1, bool pipe_stdin=true, bool pipe_stdout=true, bool
	   pipe_stderr=true)
	   Create a process with one argument.
       static Glib::RefPtr< process > create (std::string const &command, std::string const &a1, std::string const &a2, bool pipe_stdin=true, bool
	   pipe_stdout=true, bool pipe_stderr=true)
	   Create a process with two arguments.
       static Glib::RefPtr< process > create (std::string const &command, std::string const &a1, std::string const &a2, std::string const &a3,
	   bool pipe_stdin=true, bool pipe_stdout=true, bool pipe_stderr=true)
	   Create a process with three arguments.
       static Glib::RefPtr< process > create (std::string const &command, std::string const &a1, std::string const &a2, std::string const &a3,
	   std::string const &a4, bool pipe_stdin=true, bool pipe_stdout=true, bool pipe_stderr=true)
	   Create a process with four arguments.
       static Glib::RefPtr< process > create (std::string const &command, std::string const &a1, std::string const &a2, std::string const &a3,
	   std::string const &a4, std::string const &a5, bool pipe_stdin=true, bool pipe_stdout=true, bool pipe_stderr=true)
	   Create a process with five arguments.
       static Glib::RefPtr< process > create (std::string const &command, std::string const &a1, std::string const &a2, std::string const &a3,
	   std::string const &a4, std::string const &a5, std::string const &a6, bool pipe_stdin=true, bool pipe_stdout=true, bool
	   pipe_stderr=true)
	   Create a process with six arguments.
       static Glib::RefPtr< process > create (std::string const &command, std::string const &a1, std::string const &a2, std::string const &a3,
	   std::string const &a4, std::string const &a5, std::string const &a6, std::string const &a7, bool pipe_stdin=true, bool
	   pipe_stdout=true, bool pipe_stderr=true)
	   Create a process with seven arguments.
       static Glib::RefPtr< process > create (std::string const &command, std::string const &a1, std::string const &a2, std::string const &a3,
	   std::string const &a4, std::string const &a5, std::string const &a6, std::string const &a7, std::string const &a8, bool
	   pipe_stdin=true, bool pipe_stdout=true, bool pipe_stderr=true)
	   Create a process with eight arguments.
       static Glib::RefPtr< process > create (std::string const &command, std::string const &a1, std::string const &a2, std::string const &a3,
	   std::string const &a4, std::string const &a5, std::string const &a6, std::string const &a7, std::string const &a8, std::string const
	   &a9, bool pipe_stdin=true, bool pipe_stdout=true, bool pipe_stderr=true)
	   Create a process with nine arguments.

Detailed Description
       Create a process, optionally connection its standard in- and output streams to the calling program.

Member Function Documentation
   static std::string shevek::process::run (std::string const &command, std::string const &sh) [static]
       Run a process and return its output. A convenience function for running a process and catching its standard output in a string. This blocks
       until the process has exited.

   static Glib::RefPtr<process> shevek::process::shell (std::string const &command, boolpipe_stdin = true, boolpipe_stdout = true, boolpipe_stderr
       = true, std::string const &sh = '/bin/sh') [inline, static]
       Run a string with the shell. Note that the process is forked from the shell, and so does not get killed when the process goes away.

Author
       Generated automatically by Doxygen for libshevek from the source code.

libshevek							  Fri May 11 2012						shevek::process(3)
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