c++ compiler and standard library ( GCC & libstdc++, LLVM & libc++

Read through markdown version: https://github.com/shannon112/cpp-is-a-good-person/blob/main/Concept/compiler_and_stdlib.md

org	compiler	official site
LLVM	clang / clang++	https://clang.llvm.org/
GNC	gcc / g++	https://gcc.gnu.org/.

org	library	file	official site
LLVM	"libc++” C++ Standard Library (clang++ stdlib default)	libc++.so and libc++abi.so	https://libcxx.llvm.org/
GNC	The GNU C++ Library (g++ stdlib default)	libstdc++	https://gcc.gnu.org/onlinedocs/libstdc++/
GNC	The GNU C Library (glibc)	libc.so	https://www.gnu.org/software/libc/
GNC	The GCC low-level runtime library	libgcc.a or libgcc_s.so	https://gcc.gnu.org/onlinedocs/gccint/Libgcc.html

LLVM

• The LLVM project has multiple components. The core of the project is itself called “LLVM”. This contains all of the tools, libraries, and header files needed to process intermediate representations and converts it into object files. Tools include an assembler, disassembler, bitcode analyzer, and bitcode optimizer. It also contains basic regression tests. https://llvm.org/docs/GettingStarted.html
• C-like languages use the Clang front end. This component compiles C, C++, Objective C, and Objective C++ code into LLVM bitcode – and from there into object files, using LLVM.
• Other components include: the libc++ C++ standard library, the LLD linker, and more.

GCC (GNU)

• The GNU Compiler Collection includes front ends for C, C++, Objective-C, Fortran, Ada, Go, and D, as well as libraries for these languages (libstdc++,...). GCC was originally written as the compiler for the GNU operating system. The GNU system was developed to be 100% free software, free in the sense that it respects the user's freedom. https://gcc.gnu.org/

Discussion about cross using

• https://stackoverflow.com/questions/19774778/when-is-it-necessary-to-use-the-flag-stdlib-libstdc
• g++ with libstdc++ (by default)

  g++ test.cpp -std=c++17
  

• g++ with libc++

  g++ -nostdinc++ -I<libcxx-install-prefix>/include/c++/v1 \
       test.cpp -nodefaultlibs -lc++ -lc++abi -lm -lc -lgcc_s -lgcc
  

• clang++ with libc++ (by default)

  clang++ test.cpp -std=c++17
  clang++ test.cpp -stdlib=libc++
  

• clang++ with libstdc++

  clang++ test.cpp -stdlib=libstdc++
  

Discussion about gcc v.s. g++

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

Check

• Print the lists of directories and candidate libraries stored in the current cache https://linux.die.net/man/8/ldconfig

  ldconfig -p | grep <library>`
  

• Display information about ELF files (find the shared libraries that are needed to the executable file) https://man7.org/linux/man-pages/man1/readelf.1.html

  readelf -d <executable_file>
  

• Check version

  gcc --version
  g++ --version
  clang --version
  clang++ --version
  

• Check location

  which gcc
  which g++
  which clang
  which clang++