Chapter 3.  Compiling and Building

Procedure 3.1. Compiling a 'Hello World' C Program

1. Compile Example 3.1, “hello.c” into an executable with:

   ~]$ gcc hello.c -o hello

   Ensure that the resulting binary hello is in the same directory as hello.c.
2. Run the hello binary, that is, ./hello.

Procedure 3.2. Compiling a 'Hello World' C++ Program

1. Compile Example 3.2, “hello.cc” into an executable with:

   ~]$ g++ hello.cc -o hello

   Ensure that the resulting binary hello is in the same directory as hello.cc.
2. Run the hello binary, that is, ./hello.

Procedure 3.3. Compiling a Program with Multiple Source Files

1. Compile Example 3.3, “one.c” into an executable with:

   ~]$ gcc -c one.c -o one.o

   Ensure that the resulting binary one.o is in the same directory as one.c.
2. Compile Example 3.4, “two.c” into an executable with:

   ~]$ gcc -c two.c -o two.o

   Ensure that the resulting binary two.o is in the same directory as two.c.
3. Compile the two object files one.o and two.o into a single executable with:

   ~]$ gcc one.o two.o -o hello

   Ensure that the resulting binary hello is in the same directory as one.o and two.o.
4. Run the hello binary, that is, ./hello.

Procedure 3.4. Using Profile Feedback

1. The application must be instrumented to produce profiling information by compiling it with -fprofile-generate.
2. Run the application to accumulate and save the profiling information.
3. Recompile the application with -fprofile-use.

Procedure 3.5. Compiling a Program with Profiling Feedback

1. Compile source.c to include profiling instrumentation:
   gcc source.c -fprofile-generate -O2 -o executable
2. Run executable to gather profiling information:
   ./executable
3. Recompile and optimize source.c with profiling information gathered in step one:
   gcc source.c -fprofile-use -O2 -o executable

Procedure 3.6. Compiling a 32-bit Program on a 64-bit Host

1. On a 64-bit system, compile hello.c into a 64-bit executable with:
   gcc hello.c -o hello64
2. Ensure that the resulting executable is a 64-bit binary:

                 $ file hello64
                 hello64: ELF 64-bit LSB executable, x86-64, version 1 (GNU/Linux), dynamically linked (uses shared libs), for GNU/Linux 2.6.18, not stripped
                 $ ldd hello64
                 linux-vdso.so.1 =>  (0x00007fff242dd000)
                 libc.so.6 => /lib64/libc.so.6 (0x00007f0721514000)
                 /lib64/ld-linux-x86-64.so.2 (0x00007f0721893000)
   

   The command file on a 64-bit executable will include ELF 64-bit in its output, and ldd will list /lib64/libc.so.6 as the main C library linked.
3. On a 64-bit system, compile hello.c into a 32-bit executable with:
   gcc -m32 hello.c -o hello32
4. Ensure that the resulting executable is a 32-bit binary:

                 $ file hello32
                 hello32: ELF 32-bit LSB executable, Intel 80386, version 1 (GNU/Linux), dynamically linked (uses shared libs), for GNU/Linux 2.6.18, not stripped
                 $ ldd hello32
                 linux-gate.so.1 =>  (0x007eb000)
                 libc.so.6 => /lib/libc.so.6 (0x00b13000)
                 /lib/ld-linux.so.2 (0x00cd7000)
   

   The command file on a 32-bit executable will include ELF 32-bit in its output, and ldd will list /lib/libc.so.6 as the main C library linked.