Skip to content

Latest commit

 

History

History
57 lines (32 loc) · 2.15 KB

introduction.md

File metadata and controls

57 lines (32 loc) · 2.15 KB
Raw

Introduction

GCC is arguably the most popular C and C++ compiler.

GCC stands for GNU Compiler Collection: not C compiler, and currently compiles: C, C++, Objective-C, Fortran, Java, Ada, and Go.

The Linux kernel uses GCC extensions so you need it to build it.

gcc is the C compiler. It is a large frontend for other tools such as as, cpp.

gcc and g++ are the dominant compilers on Linux. Important alternatives include clang and Intel's icc.

Only language extension are discussed: glibc extensions are not. Language extensions are documented at: https://gcc.gnu.org/onlinedocs/gcc/C-Extensions.html

You can disable all non-GNU specific languages features with flags like -ansi or -std=c99, which you should always do. This will not however stop defining certain GNU specific preprocessor macros such as __GNUC__

Obviously, it is always better if you avoid using extensions, but you may encounter them in Linux specific projects, such as the Linux kernel itself for example.

GNU extensions have a large chance of being implemented in future ANSI C versions (but sometimes in a modified form) because of the large influence of GCC.

g++ vs gcc

g++: http://stackoverflow.com/questions/172587/what-is-the-difference-between-g-and-gcc

Most important differences:

  • g++ treats both .c and .cpp files as C++, since .c is backwards compatible with C++, it works
  • g++ links to (but does not include) stdlib automatically, gcc does not!

Supported executable formats

Major ones:

  • ELF (Linux)
  • Mach-O (Mac OS)
  • PE (Windows)

but there are others.

What languages it compiles

GCC has front-ends and back-ends:

  • front-ends: input languages
  • back-ends: output machine codes

Infrastructure is reused across multiple languages.

Front-ends for which GCC is the major Linux implementation: C, C++, Fortran, Ada.

Other front-ends:

  • Java (deprecated), Oracle's javac
  • Go, Google's gc
  • Objective-C: TODO. What does Apple use? There is also a LLVM

GCC also offers standard libraries for most languages it supports, except libc, which is in the separate project glibc, which is highly optimized, and has per-processor implementations.