理解g++、GCC、GDB、GNU以及各种后缀

• language translate

  There are 4 phases for a Program to finally get translated into an executable file viz:

  1. Preprocessing : It expands the code (For example - expansion of macros, removal of comments and conditional compilation)
  2. Compilation : Translates the code into assembly language, which an assembler can understand
  3. Assembly : Assembler translates the code into machine code or byte code
  4. Linking : It links various modules of the code, i.e. the function calls and finally delivers the executable

• Compiler VS. Interpreter

  Compiler : Scans the entire program and translates it as a whole into machine code. It continues translating the program until the first error is met, in which case it stops. Hence debugging is easy. For example Java.

  Interpreter : Translates program one statement at a time and does not generate Object Code. It gives error only after scanning the entire program. For example Python.

• GUN

  GUN, recursive acronym for “GUN’s Not Unix”, is a Unix-like operating system and free software under General Public License(GPL). It is intended to develop and share software for free, for all its users.

• GCC

  GCC(GNU Compiler Collection) is a compiler system produced by the GNU Project under General Puublic License, supports various programming languages.

  Earlier it was named GNU C Compiler as it only supported C programming language. GCC can compile both C and C++ files(for example .c/.cpp files).

  It provides various options, for example:

  • -o Option (to specify the output name for the executable)
  • -wall Option(to enable warnings)
  • -e Option (to produce preprocessor output)
  • -S Option (file would contain the assembly output)
  • -c Option (file would contain machine code)

  gcc sourcecode.c -o executable
  # The gcc will stop compiling the program after the hello.s file is generated
  gcc -S hello.c
  

  GNU project C and C++ compiler, a GNU compiler collection.

  gcc [options] file ...
  

  The whole list of gcc compiler commands and options:

  Options	meaning
  -pass-exit-codes	Exit with highest error code from a phase
  –help	Display this information
  –target-help	Display target specific command line options (Use ‘-v --help’ to display command line options of sub-processes)
  -dumpspecs	Display all of the built in spec strings
  -dumpversion	Display the version of the compiler
  -dumpmachine	Display the compiler’s target processor
  -print-search-dirs	Display the directories in the compiler’s search path
  -print-libgcc-file-name	Display the name of the compiler’s companion library
  -print-file-name=	Display the full path to library
  -print-prog-name=	Display the full path to compiler component
  -print-multi-directory	Display the root directory for versions of libgcc
  -print-multi-lib	Display the mapping between command line options and multiple library search directiories
  -print-multi-os-directory	Display the relative path to OS libraries
  -Wa,	Pass comma-separated on to the assembler
  -Wp,	Pass comma-separated on to the preprocessor
  -Wl,	Pass comma-separated on to the linker
  -Xassembler	Pass on to the assembler
  -Xpreprocessor	Pass on to the preprocessor
  -Xlinker	Pass on to linker
  -save-temps	Do not delete intermediate files
  -pipe	Use pipes rather than intermediate files
  -time	Time the execution of each sub process
  -specs=	Override built-in specs with the contents of
  -std=	Assume that the input sources are for
  -B	Add to the compiler’s search paths
  -b	Run gcc for target , if installed
  -V	Run gcc version number , if installed
  -v	Display the programs invoked by the compiler
  -###	Like -v but options quoted and commands not executed
  -E	Preprocess only; do not compile, assemble or link
  -S	Compile only; do not assemble or link
  -c	Compile and assemble, but do not link
  -o	Place the output into
  -x	Specify the language of the following input files Permissible languages include:c c++ assembler none. ‘none’ means revert to the default behavior of guessing the language based on the file’s extension

  Options starting with -g, -f, -m, -O, -W, or --param are automatically passed on to the various sub-processes invoked by gcc. In order to pass other options on to these processes the -W options must be used.

  If you have more object files to be linked together during the linking process, it is better to create the makefile.

• g++

  To compile C++ codes you may use the g++, g++ accepts mostly the same options as gcc.

  G++ (GNU C++ Compiler) is a GUN C++ compiler invocation command, which is used for preprocessing, cimpilation, assembly and linking of source code to generate an executable file. It provides a similar set of options as defined for GCC to get output invarious intermediate stages of code compilation.

  g++ -o main.exe hello.cpp 
  

• GDB debugger

  GNU Debugger (GDB) is a portable debugging tool for C and many other programming languages and runs on Unix-like operating systems.

  This tool comes in handy when our C program crashes and to know what exactly wrong has happened inside the code.

  GUN Debugger executes on the binary files/executables. It provides a GDB prompt which opens after typing gdb in your Linux terminal, where you can operate it using the commands it provides.

  Some commands that GDB provides:

  • r (run) — to execute the program from start till the very end.
  • b (break) — provides breakpoint on a particular line to debug the code.
  • disable — to disable a breakpoint.
  • enable — to enable a disabled breakpoint.
  • n (next) — go to next line of code, not into functions.
  • step — go to next instruction, diving into functions.
  • l (list) — displays the code.
  • p (print) — to display the stored value.
  • q (quit) — to exit the GDB prompt.
  • clear — clears all breakpoints.
  • continue — continues normal execution of code.

• 各类后缀名

  Typically, the executable doesn’t have extension.

  File extension	Description
  file_name.c	C source code which must be preprocessed
  file_name.i	C source code which should not be preprocessed
  file_name.ii	C++ source code which should not be preprocessed
  file_name.h	C header file (not to be compiled or linked)
  file_name.cc file_name.cp file_name.cxx file_name.cpp file_name.c++ file_name.C	C++ source code which must be preprocessed. For file_name.cxx, the xx must both be literally character x and file_name.C, is capital c.
  file_name.s	Assembler code
  file_name.S	Assembler code which must be preprocessed
  file_name.o	Object file by default, the object file name for a source file is made by replacing the extension .c,.i,.s etc with .o

• Reference

1. GNU, GCC, G++, GDB — What are these terms? Explained!!
2. gcc/g++常用编译选项和gdb常用调试命令
3. MODULE 000-1 GCC, G++, GDB AND FRIENDS 1