Actual submission

exercises/ex01/hello.c

@@ -1,10 +1,230 @@
 #include <stdio.h>
 
+void printSomething() {
+	puts("Something");
+}
+
 int main() {
-    int x = 5;
-    int y = x + 1;
-    printf(y);
+	char b[10];
+	char a = b[100];
+	printf("%i\n", a);
+//	int x = 5;
+//	int y = x + 1;
+//    printf("Hello, World! %i\n", y);
+//    printSomething();
+//
+//    int a = 3;
+//    int b = 4;
+//    int c = ab() + b;
+//    printf("c is %d\n", c);
     return 0;
 }
 
-% probably takes up less memory and makes it so that we need fewer operations
+/*
+ * 1. This is the output I received:
+ * 	.file	"hello.c"
+	.section	.rodata
+.LC0:
+	.string	"Hello, World!"
+	.text
+	.globl	main
+	.type	main, @function
+main:
+.LFB0:
+	.cfi_startproc
+	pushq	%rbp
+	.cfi_def_cfa_offset 16
+	.cfi_offset 6, -16
+	movq	%rsp, %rbp
+	.cfi_def_cfa_register 6
+	subq	$16, %rsp
+	movl	$5, -4(%rbp) <---- Here is where I think the code that corresponds to this line is
+	leaq	.LC0(%rip), %rdi
+	call	puts@PLT
+	movl	$0, %eax
+	leave
+	.cfi_def_cfa 7, 8
+	ret
+	.cfi_endproc
+.LFE0:
+	.size	main, .-main
+	.ident	"GCC: (Ubuntu 6.3.0-12ubuntu2) 6.3.0 20170406"
+	.section	.note.GNU-stack,"",@progbits
+ *
+ *
+ * ----------------------------------------------------------------------------
+ *
+ *
+ * 2. This is the output I received with the optimization flag -O2:
+ * 	.file	"hello.c"
+	.section	.rodata.str1.1,"aMS",@progbits,1
+.LC0:
+	.string	"Hello, World!"
+	.section	.text.startup,"ax",@progbits
+	.p2align 4,,15
+	.globl	main
+	.type	main, @function
+main:
+.LFB23:
+	.cfi_startproc
+	leaq	.LC0(%rip), %rdi
+	subq	$8, %rsp
+	.cfi_def_cfa_offset 16
+	call	puts@PLT
+	xorl	%eax, %eax
+	addq	$8, %rsp
+	.cfi_def_cfa_offset 8
+	ret
+	.cfi_endproc
+.LFE23:
+	.size	main, .-main
+	.ident	"GCC: (Ubuntu 6.3.0-12ubuntu2) 6.3.0 20170406"
+	.section	.note.GNU-stack,"",@progbits
+ *
+ * It looks like the line disappeared (probably because I wasn't using the value of x at all).
+ *
+ * ----------------------------------------------------------------------------
+ *
+ *
+ * 3. These are the outputs I received:
+ * Printing X, not optimized:
+ * 	.file	"hello.c"
+	.section	.rodata
+.LC0:
+	.string	"Hello, World! %i\n"
+	.text
+	.globl	main
+	.type	main, @function
+main:
+.LFB0:
+	.cfi_startproc
+	pushq	%rbp
+	.cfi_def_cfa_offset 16
+	.cfi_offset 6, -16
+	movq	%rsp, %rbp
+	.cfi_def_cfa_register 6
+	subq	$16, %rsp
+	movl	$5, -4(%rbp)
+	movl	-4(%rbp), %eax
+	movl	%eax, %esi
+	leaq	.LC0(%rip), %rdi
+	movl	$0, %eax
+	call	printf@PLT
+	movl	$0, %eax
+	leave
+	.cfi_def_cfa 7, 8
+	ret
+	.cfi_endproc
+.LFE0:
+	.size	main, .-main
+	.ident	"GCC: (Ubuntu 6.3.0-12ubuntu2) 6.3.0 20170406"
+	.section	.note.GNU-stack,"",@progbits
+ *
+ * Printing X, optimized:
+ * 	.file	"hello.c"
+	.section	.rodata.str1.1,"aMS",@progbits,1
+.LC0:
+	.string	"Hello, World! %i\n"
+	.section	.text.startup,"ax",@progbits
+	.p2align 4,,15
+	.globl	main
+	.type	main, @function
+main:
+.LFB23:
+	.cfi_startproc
+	leaq	.LC0(%rip), %rsi
+	subq	$8, %rsp
+	.cfi_def_cfa_offset 16
+	movl	$5, %edx
+	movl	$1, %edi
+	xorl	%eax, %eax
+	call	__printf_chk@PLT
+	xorl	%eax, %eax
+	addq	$8, %rsp
+	.cfi_def_cfa_offset 8
+	ret
+	.cfi_endproc
+.LFE23:
+	.size	main, .-main
+	.ident	"GCC: (Ubuntu 6.3.0-12ubuntu2) 6.3.0 20170406"
+	.section	.note.GNU-stack,"",@progbits
+ *
+ * The 5 is back because I'm using it now in the print statement!
+ *
+ *
+ * ----------------------------------------------------------------------------
+ *
+ *
+ * 4. Here are the outputs I received:
+ * Without optimization:
+ *
+ * 	.file	"hello.c"
+	.section	.rodata
+.LC0:
+	.string	"Hello, World! %i\n"
+	.text
+	.globl	main
+	.type	main, @function
+main:
+.LFB0:
+	.cfi_startproc
+	pushq	%rbp
+	.cfi_def_cfa_offset 16
+	.cfi_offset 6, -16
+	movq	%rsp, %rbp
+	.cfi_def_cfa_register 6
+	subq	$16, %rsp
+	movl	$5, -8(%rbp)
+	movl	-8(%rbp), %eax
+	addl	$1, %eax
+	movl	%eax, -4(%rbp)
+	movl	-4(%rbp), %eax
+	movl	%eax, %esi
+	leaq	.LC0(%rip), %rdi
+	movl	$0, %eax
+	call	printf@PLT
+	movl	$0, %eax
+	leave
+	.cfi_def_cfa 7, 8
+	ret
+	.cfi_endproc
+.LFE0:
+	.size	main, .-main
+	.ident	"GCC: (Ubuntu 6.3.0-12ubuntu2) 6.3.0 20170406"
+	.section	.note.GNU-stack,"",@progbits
+ *
+ *
+ * With optimization:
+ * 
+ * 	.file	"hello.c"
+	.section	.rodata.str1.1,"aMS",@progbits,1
+.LC0:
+	.string	"Hello, World! %i\n"
+	.section	.text.startup,"ax",@progbits
+	.p2align 4,,15
+	.globl	main
+	.type	main, @function
+main:
+.LFB23:
+	.cfi_startproc
+	leaq	.LC0(%rip), %rsi
+	subq	$8, %rsp
+	.cfi_def_cfa_offset 16
+	movl	$6, %edx
+	movl	$1, %edi
+	xorl	%eax, %eax
+	call	__printf_chk@PLT
+	xorl	%eax, %eax
+	addq	$8, %rsp
+	.cfi_def_cfa_offset 8
+	ret
+	.cfi_endproc
+.LFE23:
+	.size	main, .-main
+	.ident	"GCC: (Ubuntu 6.3.0-12ubuntu2) 6.3.0 20170406"
+	.section	.note.GNU-stack,"",@progbits
+ *
+ * The value of X and Y are shown without optimization, but the value of X disappears with optimization.
+ *
+ * Optimization must remove unnecessary values in some way or another; if the value of X isn't printed later in the code, for example, it just disappears from the assembly language output.
+ */