check in assembly files, fix some comments, remove unused function

tests/chapter_18/valid/no_structure_parameters/size_and_offset_calculations/member_offsets.c

@@ -1,6 +1,6 @@
 /* Get the addresses of structure members to validate their offset and alignment
  * (including nested members accessed through chains of . and -> operations)
- * and addresses one-past-the-end of structs to validate trailing padding
+ * and addresses of one-past-the-end of structs to validate trailing padding
  * */
 #include "struct_sizes.h"
 

tests/chapter_18/valid/no_structure_parameters/struct_copy/copy_struct_through_pointer.c

@@ -70,7 +70,7 @@ int test_copy_to_array_elem(void) {
     return 1;  // success
 }
 
-// case 5: arr[i] = x
+// case 5: x = arr[i]
 int test_copy_from_array_elem(void) {
     struct s arr[3] = {
         {"ab", {-3000, -4000}}, {"cd", {-5000, -6000}}, {"ef", {-7000, -8000}}};

tests/chapter_18/valid/params_and_returns/big_data_on_page_boundary_linux.s

@@ -0,0 +1,7 @@
+    .bss        # .bss is the last segment in the program image - the page after it will be unampped
+    .align 4096 # force page alignment
+    .zero 4078  # write a bunch of zeros so on_page_boundary is at the end of the page
+    .globl on_page_boundary
+on_page_boundary:
+    .zero 18
+    .section	".note.GNU-stack","",@progbits

tests/chapter_18/valid/params_and_returns/big_data_on_page_boundary_osx.s

@@ -0,0 +1,6 @@
+    .bss        # .bss is the last segment in the program image - the page after it will be unampped
+    .align 12   # force page alignment (2^12 == 4096)
+    .zero 4078  # write a bunch of zeros so on_page_boundary is at the end of the page
+    .globl _on_page_boundary
+_on_page_boundary:
+    .zero 8

tests/chapter_18/valid/params_and_returns/libraries/return_calling_conventions.c

@@ -32,12 +32,6 @@ struct memory return_on_stack(void) {
     return retval;
 }
 
-int f(char c, double d) {
-    if (c == 'p' && d == 4.56)
-        return 0;
-    return 1;
-}
-
 int leaf_call(struct two_ints t_i, char c, double d) {
     // validate t_i
     if (t_i.c != '_' || t_i.arr[0] != 5 || t_i.arr[1] != 6 || t_i.arr[2] != 7) {

tests/chapter_18/valid/params_and_returns/return_space_address_overlap_linux.s

@@ -0,0 +1,75 @@
+	# validate that space allocated for return address does not overlap
+	# with storage for other objects we can access from callee (this is an ABI requirement)
+	# case 1: overlap w/ global variable
+	.data
+	.globl globvar
+	.align 8
+globvar:
+	.zero 24
+	.text
+	# globvar = overlap_with_globvar()
+	.globl overlap_with_globvar
+overlap_with_globvar:
+	# load address of globvar into RSI
+	leaq	globvar(%rip),	%rsi
+	# make sure return address (in RDI) and globvar's address (in RSI)
+	# are at least 24 bytes apart
+	subq	%rdi, %rsi
+	# get absolute value of difference between addresses (in RSI)
+	# (absolute value implementation from https://stackoverflow.com/a/11927940)
+	movq	%rsi, %rcx	# copy RSI into RCX
+	negq	%rsi	# negate RSI
+	# if RSI is now negative, its restore original (positive) value
+	cmovl	%rcx, %rsi
+	# compare diference to 24
+	cmpq	$24, %rsi
+	jl	.Loverlap_detected
+	# no overlap, so go ahead and return value
+	movq	$400, (%rdi)
+	movq	$500, 8(%rdi)
+	movq	$600, 16(%rdi)
+	movq	%rdi, %rax
+	ret
+.Loverlap_detected:
+	# space for return value overlaps w/ globvar, so exit with error code
+	movl	$1, %edi
+	call	exit
+
+	# case 2: overlap w/ pointer passed as arg
+	# x = overlap_with_pointer(&x)
+	.globl	overlap_with_pointer
+overlap_with_pointer:
+	# copy pointer into RDX
+	leaq	globvar(%rip), %rdx
+	# make sure return address (in RDI) and globvar's address (in RDX)
+	# are at least 24 bytes apart
+	subq	%rdi, %rdx
+	# get absolute value of difference between addresses (in RDX)
+	# (absolute value implementation from https://stackoverflow.com/a/11927940)
+	movq	%rdx, %rcx	# copy RDX into RCX
+	negq	%rdx			# negate RDX
+	# if rdx is now negative, its restore original (positive) value
+	cmovl	%rcx, %rdx
+	# compare diference to 24
+	cmpq	$24, %rdx
+	jl	.Loverlap_detected.0
+	# no overlap, so go ahead and return value
+	# set each member to twice its original value (accessed thru RSI)
+	# l1
+	movq	(%rsi), %rcx
+	imul	$2, %rcx
+	movq	%rcx, (%rdi)
+	# l2
+	movq	8(%rsi), %rcx
+	imul	$2, %rcx
+	movq	%rcx, 8(%rdi)
+	# l3
+	movq	16(%rsi), %rcx
+	imul	$2, %rcx
+	movq	%rcx, 16(%rdi)
+	movq	%rdi, %rax
+	ret
+.Loverlap_detected.0:
+	# space for return value overlaps w/ space pointed to by argument, so exit with error code
+	movl	$3, %edi
+	call	exit

tests/chapter_18/valid/params_and_returns/return_space_address_overlap_osx.s

@@ -0,0 +1,75 @@
+	# validate that space allocated for return address does not overlap
+	# with storage for other objects we can access from callee (this is an ABI requirement)
+	# case 1: overlap w/ global variable
+	.data
+	.globl _globvar
+	.align 3
+_globvar:
+	.zero 24
+	.text
+	# globvar = overlap_with_globvar()
+	.globl _overlap_with_globvar
+_overlap_with_globvar:
+	# load address of globvar into RSI
+	leaq	_globvar(%rip),	%rsi
+	# make sure return address (in RDI) and globvar's address (in RSI)
+	# are at least 24 bytes apart
+	subq	%rdi, %rsi
+	# get absolute value of difference between addresses (in RSI)
+	# (absolute value implementation from https://stackoverflow.com/a/11927940)
+	movq	%rsi, %rcx	# copy RSI into RCX
+	negq	%rsi	# negate RSI
+	# if RSI is now negative, its restore original (positive) value
+	cmovl	%rcx, %rsi
+	# compare diference to 24
+	cmpq	$24, %rsi
+	jl	Loverlap_detected
+	# no overlap, so go ahead and return value
+	movq	$400, (%rdi)
+	movq	$500, 8(%rdi)
+	movq	$600, 16(%rdi)
+	movq	%rdi, %rax
+	ret
+Loverlap_detected:
+	# space for return value overlaps w/ globvar, so exit with error code
+	movl	$1, %edi
+	call	_exit
+
+	# case 2: overlap w/ pointer passed as arg
+	# x = overlap_with_pointer(&x)
+	.globl	_overlap_with_pointer
+_overlap_with_pointer:
+	# copy pointer into RDX
+	movq	%rsi, %rdx
+	# make sure return address (in RDI) and pointer's address (in RDX)
+	# are at least 24 bytes apart
+	subq	%rdi, %rdx
+	# get absolute value of difference between addresses (in RDX)
+	# (absolute value implementation from https://stackoverflow.com/a/11927940)
+	movq	%rdx, %rcx	# copy RDX into RCX
+	negq	%rdx			# negate RDX
+	# if rdx is now negative, its restore original (positive) value
+	cmovl	%rcx, %rdx
+	# compare diference to 24
+	cmpq	$24, %rdx
+	jl	Loverlap_detected.0
+	# no overlap, so go ahead and return value
+	# set each member to twice its original value (accessed thru RSI)
+	# l1
+	movq	(%rsi), %rcx
+	imul	$2, %rcx
+	movq	%rcx, (%rdi)
+	# l2
+	movq	8(%rsi), %rcx
+	imul	$2, %rcx
+	movq	%rcx, 8(%rdi)
+	# l3
+	movq	16(%rsi), %rcx
+	imul	$2, %rcx
+	movq	%rcx, 16(%rdi)
+	movq	%rdi, %rax
+	ret
+Loverlap_detected.0:
+	# space for return value overlaps w/ space pointed to by argument, so exit with error code
+	movl	$3, %edi
+	call	_exit