The GNU Compiler Collection contains frontends for C, C++, Objective-C, Fortran, Java, and Ada as well as libraries for these languages. It is a full-featured ANSI C compiler with support for K&R C as well. GCC provides many levels of source code error checking traditionally provided by other tools (such as lint), produces debugging information, and can perform many different optimizations to the resulting object code.
Eric is a full featured Python and Ruby editor and IDE, written in Python. It is based on the cross platform Qt GUI toolkit, integrating the highly flexible Scintilla editor control. It is designed to be usable as an everyday quick and dirty editor as well as being usable as a professional project management tool, integrating many advanced features that Python offers the professional coder. Eric includes a plug-in system, which allows easy extension of the IDE functionality with plug-ins downloadable from the net. Current stable versions are Eric4 based on Qt4 and Python 2 and Eric5 based on Python 3 and Qt4.
ltrace is a debugging program which runs a specified command until it exits. While the command is executing, ltrace intercepts and records the dynamic library calls which are called by the executed process and the signals received by that process. It can also intercept and print the system calls executed by the program. The program to be traced need not be recompiled for this, so you can use it on binaries for which you don't have the source handy. You should install ltrace if you need a sysadmin tool for tracking the execution of processes.
FTPL (FakeTime Preload Library, aka libfaketime) intercepts various system library calls and tricks programs of your choice into seeing a faked system time without having to change the time system-wide. This can be used for running legacy software with Y2K bugs, testing software for year-2038 compliance, debugging time-related issues such as expired SSL certificates, and using software that ceases to run outside a certain time frame. The faked time can be specified either absolutely or relative to the real current time, and optionally also affects file timestamps. The faked clock continues to run, but can optionally be frozen, slowed down, or made faster. A wrapper script "faketime" simplifies the usage, similar to tools such as fakechroot.
The GNU Debugger (GDB) is a source-level debugger for C, C++, Java, Modula-2, and several other languages. It runs on GNU/Linux, the BSD's, and almost every major proprietary OS. GDB can debug programs running on the same machine as itself, or it can communicate over a network or serial line with a debugging stub on another machine; thus, it can be used for embedded and kernel debugging.
Arcadia is a Light Integrated Development Environment (IDE) for the Ruby language written in Ruby using the classic Tcl/Tk GUI toolkit. Some features include an editor with source browsing, syntax highlighting, and code completion, debug support, the ability to work on any platform where Ruby and Tcl-Tk work, a highly extensibility architecture, and support for RAD GUI building.