Build with gcc - otherwise we'd need to dynamically link the librarie…

…s manually:

  ld -dynamic-linker /lib/ld-linux.so.2 -o cpuid2 -lc cpuid2.o

Change the _start symbol to main for usage with gcc (alternatively, we could specify the flag could to gcc)

ch04/Rakefile

@@ -1,15 +1,13 @@
 task :default => :compile
 
-PROGS = ["cpuid"]
+PROGS = ["cpuid", "cpuid2"]
 ASM_FLAGS = []
 
 task :compile do
-  PROGS.each do |prog|
-    sh [
-     "as #{ASM_FLAGS.join(" ")} -o #{prog}.o #{prog}.s",
-     "ld -o #{prog} #{prog}.o"
-    ].join(" && ")
-  end
+  asm_flags = ASM_FLAGS.join
+
+  sh "as #{asm_flags} -o cpuid.o  cpuid.s  && ld -o cpuid  cpuid.o"
+  sh "gcc -o cpuid2 cpuid2.s"
 end
 
 task :compile_debug do

ch04/cpuid2.s

@@ -10,8 +10,8 @@ output:
   .lcomm buffer, 12
 
 .section .text
-.globl _start
-_start:
+.globl main
+main:
 
   # same as before
   nop