test struct init

a.c

#include <stdio.h>

struct test {
    int a, b, c;
};

int main() {
    struct test st = {
        .b = 15,
    };
    printf("%d %d %d", st.a, st.b, st.c);
    return 0;
}

a.s

	.file	"a.c"
	.section	.rodata
.LC0:
	.string	"%d %d %d"
	.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
	movq	$0, -16(%rbp)  // st.a = st.b = 0
	movl	$0, -8(%rbp)   // st.c = 0
	movl	$15, -12(%rbp) // st.b
	movl	-8(%rbp), %ecx
	movl	-12(%rbp), %edx
	movl	-16(%rbp), %eax
	movl	%eax, %esi
	movl	$.LC0, %edi
	movl	$0, %eax
	call	printf
	movl	$0, %eax
	leave
	.cfi_def_cfa 7, 8
	ret
	.cfi_endproc
.LFE0:
	.size	main, .-main
	.ident	"GCC: (GNU) 5.2.0"
	.section	.note.GNU-stack,"",@progbits