My Objective-C collection (using GNUstep)

arc_hello.m

// ARC environment

#import <stdio.h>

int main( int argc, const char *argv[] ) {
    @autoreleasepool {
        // Code benefitting from a local autorelease pool.
        NSLog(@"Hello, World!");
    }
}

arc_test.m

// A way to test that Automatic Reference Counting (ARC) is working as expected in Objective-C
#import <stdio.h>

int main( int argc, const char *argv[] ) {
    if (__has_feature(objc_arc)) {
        printf("ARC is working.");
        return 0;
    } else {
        printf("ARC is not working.");
        return -1;
    }
}

compile.sh

#!/bin/bash

# ======================================================================
# COMPILE USING THE FOLLOWING COMMAND LINE
# ======================================================================

# Set compiler

if [ -x "$(command -v ${CC})" ]; then
  echo "Using CC from environment variable: ${CC}"
else
  if [ -x "$(command -v clang-9)" ]; then
    CC=clang-9
  elif [ -x "$(command -v clang-8)" ]; then
    CC=clang-8
  elif [ -x "$(command -v clang-6.0)" ]; then
    CC=clang-6.0
  elif [ -x "$(command -v clang)" ]; then
    CC=clang
  else
    echo 'Error: clang seems not to be in PATH. Please check your $PATH.' >&2
    exit 1
  fi
fi

# Using COMMAND LINE
echo "Compiling and running $1."
# With ARC
${CC} `gnustep-config --objc-flags` `gnustep-config --objc-libs` -fobjc-arc -lobjc -lgnustep-base $1.m -o $1
# Without ARC
# ${CC} `gnustep-config --objc-flags` `gnustep-config --objc-libs` -lobjc -lgnustep-base $1.m -o $1
./$1

non_arc_hello.m

// Non-ARC environment

#import <stdio.h>

int main( int argc, const char *argv[] ) {
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
    // Code benefitting from a local autorelease pool.
    NSLog(@"Hello, World!");
    [pool release];
}