The GNU Debugger, usually called just GDB, is the standard debugger for the GNU software system. It is a portable debugger that runs on many Unix-like systems and works for many programming languages, including C and C++.
GDB is part of the Free Software Foundation's GNU operating system. GDB was first written by Richard Stallman in 1986.
GDB offers extensive facilities for tracing and altering the execution of computer programs. The user can monitor and modify the values of programs' internal variables, and even call functions independently of the program's normal behavior.
gdb download
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here.