How variables are represented in memory

GCC 32bit compile on Mac

• The i386 architecture is deprecated for macOS
  

  $ gcc -m32 fib.c
  ld: warning: The i386 architecture is deprecated for macOS (remove from the Xcode build setting: ARCHS)
  ld: warning: ignoring file /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/lib/libSystem.tbd, missing required architecture i386 in file /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/lib/libSystem.tbd
  Undefined symbols for architecture i386:
    "_printf", referenced from:
        _main in fib-68f6b9.o
  ld: symbol(s) not found for architecture i386
  clang: error: linker command failed with exit code 1 (use -v to see invocation)
  

• Install i386 support
  

  $ sudo rm -rf /Library/Developer/CommandLineTools
  $ xcode-select --install
  $ open /Library/Developer/CommandLineTools/Packages/macOS_SDK_headers_for_macOS_10.14.pkg
  

• Compile
  

  $ gcc -m32 fib.c
  ld: warning: The i386 architecture is deprecated for macOS (remove from the Xcode build setting: ARCHS)
  

  $ make CFLAGS="-m32" fib
  cc -m32    fib.c   -o fib
  ld: warning: The i386 architecture is deprecated for macOS (remove from the Xcode build setting: ARCHS)
  

Language performance test

Lower value shows better performance

• C
  

  #include <stdio.h>
  
  int fib(int n) {
      if(n == 1) return 0;
      if(n == 2) return 1;
      return fib(n - 2) + fib(n - 1);
  }
  
  int main() {
      int i = 0;
      for(i = 1; i <= 40; i++) {
          printf("%d %d\n", i, fib(i));
      }
      printf("\nC\n");
      return 0;
  }
  

• Java
  

  public class Fib {
   
      public static int calc(int n) {
          if(n <= 1) return 0;
          if(n == 2) return 1;
          return Fib.calc(n - 2) + Fib.calc(n - 1);
      }
      public static void main(String[] args) {
          for(int i = 1; i <= 40; i++) {
              System.out.println(i + " " + Fib.calc(i));
          }
          System.out.println("\nJAVA");
      }
   
  }
  

• JavaScript
  

  #!/usr/bin/env node
  
  let range = Array.from({length: 40}, (x, i) => i+1);
  let fib = n => n === 1 ? 0 : n === 2 ? 1 : fib(n - 2) + fib(n - 1);
  
  range.forEach( i => console.log(i, fib(i)) );
  console.log("\nJavaScript");
  

• PHP
  

  #!/usr/bin/env php
  <?php
  function fib(int $n) {
      if ($n === 1) return 0;
      if ($n === 2) return 1;
      return fib($n - 2) + fib($n - 1);
  }
  
  foreach (range(1, 40) as $i) {
      echo $i, ' ', fib($i), PHP_EOL;
  }
  echo "\nPHP\n";
  

• Python
  

  #!/usr/bin/env python
  
  def fib(n):
    if n == 1:
      return 0
    elif n == 2:
      return 1
    return fib(n - 2) + fib(n - 1)
  
  if __name__ == "__main__":
    for i in range(1, 40 + 1):
      print(i, fib(i))
    print("\nPYTHON")
  

• Ruby
  

  #!/usr/bin/env ruby
  
  def fib(n)
    return 0 if n == 1
    return 1 if n == 2
    return fib(n - 2) + fib(n - 1)
  end
  
  (1..40).each do |i|
    puts "#{i.to_s} #{fib(i).to_s}"
  end
  puts "\nRUBY"
  

How to set DYLD_LIBRARY_PATH in Xcode

Open Product > Scheme > Edit Scheme > Run > Arguments
Add DYLD_LIBRARY_PATH under Environment Variables

dyld: Library not loaded: libboost_system.dylib

Got an error when compile boost library and run a sample program.

$ ./PROGRAM
dyld: Library not loaded: libboost_system.dylib
  Referenced from: /PATH/TO/PROGRAM
  Reason: image not found
Abort trap: 6

Check libraries then tried install_name_tool, but failed.

$ otool -L PROGRAM
PROGRAM:
libboost_system.dylib (compatibility version 0.0.0, current version 0.0.0)
libboost_thread.dylib (compatibility version 0.0.0, current version 0.0.0)
/usr/lib/libc++.1.dylib (compatibility version 1.0.0, current version 307.4.0)
/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1238.0.0)

$ install_name_tool -change libboost_system.dylib /PATH/TO/libboost_system.dylib PROGRAM
$ install_name_tool -change libboost_thread.dylib /PATH/TO/libboost_thread.dylib PROGRAM

Solution, add the following to .profile or .bash_profile

export DYLD_LIBRARY_PATH=/PATH/TO/BOOST/stage/lib