global_vs_heap_array.cc

struct Foo {
 int a;
 int b;
 int c;
 int d;
 int e;
 int f;
 int g;
 int h;
};

Foo g_foo[30];
Foo* g_foo_ptr;

extern void Alias(void*);

void __attribute__((noinline))  no_optimizations_please() {
 Alias(g_foo_ptr);
 Alias(g_foo);
 Alias(g_foo_ptr);
}

int main() {
 no_optimizations_please();
 g_foo[1].c = 7;
 asm volatile("nop"); // just a marker to identify the relevant assembly lines
 g_foo_ptr[1].c = 8;
 no_optimizations_please();
 return 0;
}
-----
  
$ g++ -o - -S -c -O2 test.cc
  ...
	.cfi_def_cfa_register %rbp
	callq	__Z23no_optimizations_pleasev
	movl	$7, _g_foo+40(%rip)
	## InlineAsm Start
	nop
	## InlineAsm End
	movq	_g_foo_ptr(%rip), %rax
	movl	$8, 40(%rax)
	callq	__Z23no_optimizations_pleasev
	xorl	%eax, %eax
	popq	%rbp
	retq