gcc - structures as label for debugging - c

Question

Context:
Linux 64.
I would like a way to tell gcc to keep the structure as they are when generating assembly with gcc -O0 -S -g myprog.c
By that, I mean: instead of referencing the structure by address, I would like them to be referenced by label. That would ease the parsing without reading the source code again.
So, for example:
struct mystruct{
int32_t a;
char * b;
}
would become something like:
label_mystruct:
-4(label_mystruct)
-12(label_mystruct)
and for example, referenced by:
add $56, -4(label_mystruct)
Currently, it is referenced like
.globl _main
_main:
LFB13:
LM157:
pushq %rbp #
LCFI27:
movq %rsp, %rbp#,
LCFI28:
subq $80, %rsp#,
movl %edi,-68(%rbp) # argc, argc,
movq %rsi,-80(%rbp) # argv, argv
Next line is the culprit:
movq -56(%rbp), %rdx # list, D.3781
movq -16(%rbp), %rax # arr, D.3780
movq %rdx, %rsi # D.3781,
movq %rax, %rdi # D.3780,
call _myaddhu #
I would like it to be
label_mystruct:
-4(label_mystruct)
-12(label_mystruct)
.globl _main
_main:
LFB13:
LM157:
pushq %rbp #
LCFI27:
movq %rsp, %rbp#,
LCFI28:
subq $80, %rsp#,
movl %edi,-68(%rbp) # argc, argc,
movq %rsi,-80(%rbp) # argv, argv
Now it is fine:
movq label_mystruct, %rdx # list, D.3781
movq -16(%rbp), %rax # arr, D.3780
movq %rdx, %rsi # D.3781,
movq %rax, %rdi # D.3780,
call _myaddhu #
Question:
Is that possible with gcc and without using external tools?

Answer 1

I think it's not possible, and this is by the setup used in GCC.
The problem here is that the struct here is stored on the stack and you cannot really have a label referring to something on the stack. If the struct was not on the stack it would have had a label referring to it (for example if it were a global variable).
What you have on the other hand is that GCC would generate debugging info which has information about what data is placed when running specific code. In your example it would in essense say that "when executing this code -56(%ebp) points to mystruct".
On the other hand if you would write assembler code by hand you could certainly have symbolic references to a variable. You could for example do:
#define MYSTRUCT -56(%ebp)
...
movq MYSTRUCT, %rdx
however the MYSTRUCT will be expanded and that symbol being lost during assembling the code. It would be of no help if GCC did this (except maybe that the assembler code generated by -s could be more readable), in addition GCC does not pass the assembler through preprocessor anyway (because it don't do this).

Answer 2

You get that if you put your struct into static storage. This of course alters the meaning of the code. For example, this code
struct {
int a, b;
} test;
int settest(int a, b) {
test.a = a;
test.b = b;
}
compiles to (cleaned up):
settest:
movl %edi, test(%rip)
movl %esi, test+4(%rip)
ret
.comm test,8,4
You could also try to pass the option -fverbose-asm to gcc which instructs gcc to add some annotations that might make the assembly easier to read.