How does debugger know the local variables' name?

Question

I begin to learn compiler. I know that .symtab in ELF stores information about global variables and functions, but I don't find any valid information about local variables. For those local variables that are allocated on the stack, how could a debugger know their name? Are there any helpful information in ELF?

For example, here is a stupid C code:

void printLocal(){
    char c1_loc='a';
    int i_loc=1;
    char c2_loc='b';
    double d_loc=2;
    char c3_loc='c';
    float f_loc=3;
    char c4_loc='d';
    short s_loc=4;

    printf("&c1_loc = %p\n",&c1_loc);
    printf("&i_loc = %p\n",&i_loc);
    printf("&c2_loc = %p\n",&c2_loc);
    printf("&d_loc = %p\n",&d_loc);
    printf("&c3_loc = %p\n",&c3_loc);
    printf("&f_loc = %p\n",&f_loc);
    printf("&c4_loc = %p\n",&c4_loc);
    printf("&s_loc = %p\n",&s_loc);
}

And I get the .debug_info in ELF :

 <1><490>: Abbrev Number: 19 (DW_TAG_subprogram)
    <491>   DW_AT_external    : 1
    <491>   DW_AT_name        : (indirect string, offset: 0x2b): printLocal
    <495>   DW_AT_decl_file   : 1
    <496>   DW_AT_decl_line   : 42
    <497>   DW_AT_decl_column : 6
    <498>   DW_AT_low_pc      : 0x12ff
    <4a0>   DW_AT_high_pc     : 0x129
    <4a8>   DW_AT_frame_base  : 1 byte block: 9c    (DW_OP_call_frame_cfa)
    <4aa>   DW_AT_GNU_all_tail_call_sites: 1
    <4aa>   DW_AT_sibling     : <0x527>
 <2><4ae>: Abbrev Number: 20 (DW_TAG_variable)
    <4af>   DW_AT_name        : (indirect string, offset: 0x13d): c1_loc
    <4b3>   DW_AT_decl_file   : 1
    <4b4>   DW_AT_decl_line   : 43
    <4b5>   DW_AT_decl_column : 10
    <4b6>   DW_AT_type        : <0x91>
    <4ba>   DW_AT_location    : 2 byte block: 91 52     (DW_OP_fbreg: -46)
 <2><4bd>: Abbrev Number: 20 (DW_TAG_variable)
    <4be>   DW_AT_name        : (indirect string, offset: 0xc): i_loc
    <4c2>   DW_AT_decl_file   : 1
    <4c3>   DW_AT_decl_line   : 44
    <4c4>   DW_AT_decl_column : 9
    <4c5>   DW_AT_type        : <0x65>
    <4c9>   DW_AT_location    : 2 byte block: 91 58     (DW_OP_fbreg: -40)
 <2><4cc>: Abbrev Number: 20 (DW_TAG_variable)
    <4cd>   DW_AT_name        : (indirect string, offset: 0x126): c2_loc
    <4d1>   DW_AT_decl_file   : 1
    <4d2>   DW_AT_decl_line   : 45
    <4d3>   DW_AT_decl_column : 10
    <4d4>   DW_AT_type        : <0x91>
    <4d8>   DW_AT_location    : 2 byte block: 91 53     (DW_OP_fbreg: -45)
 <2><4db>: Abbrev Number: 20 (DW_TAG_variable)
    <4dc>   DW_AT_name        : (indirect string, offset: 0xce): d_loc
    <4e0>   DW_AT_decl_file   : 1
    <4e1>   DW_AT_decl_line   : 46
    <4e2>   DW_AT_decl_column : 12
    <4e3>   DW_AT_type        : <0x334>
    <4e7>   DW_AT_location    : 2 byte block: 91 60     (DW_OP_fbreg: -32)
 <2><4ea>: Abbrev Number: 20 (DW_TAG_variable)
    <4eb>   DW_AT_name        : (indirect string, offset: 0x333): c3_loc
    <4ef>   DW_AT_decl_file   : 1
    <4f0>   DW_AT_decl_line   : 47
    <4f1>   DW_AT_decl_column : 10
    <4f2>   DW_AT_type        : <0x91>
    <4f6>   DW_AT_location    : 2 byte block: 91 54     (DW_OP_fbreg: -44)
 <2><4f9>: Abbrev Number: 20 (DW_TAG_variable)
    <4fa>   DW_AT_name        : (indirect string, offset: 0x32d): f_loc
    <4fe>   DW_AT_decl_file   : 1
    <4ff>   DW_AT_decl_line   : 48
    <500>   DW_AT_decl_column : 11
    <501>   DW_AT_type        : <0x364>
    <505>   DW_AT_location    : 2 byte block: 91 5c     (DW_OP_fbreg: -36)
 <2><508>: Abbrev Number: 20 (DW_TAG_variable)
    <509>   DW_AT_name        : (indirect string, offset: 0x159): c4_loc
    <50d>   DW_AT_decl_file   : 1
    <50e>   DW_AT_decl_line   : 49
    <50f>   DW_AT_decl_column : 10
    <510>   DW_AT_type        : <0x91>
    <514>   DW_AT_location    : 2 byte block: 91 55     (DW_OP_fbreg: -43)
 <2><517>: Abbrev Number: 20 (DW_TAG_variable)
    <518>   DW_AT_name        : (indirect string, offset: 0x1e): s_loc
    <51c>   DW_AT_decl_file   : 1
    <51d>   DW_AT_decl_line   : 50
    <51e>   DW_AT_decl_column : 11
    <51f>   DW_AT_type        : <0x5e>
    <523>   DW_AT_location    : 2 byte block: 91 56     (DW_OP_fbreg: -42)

when I use GDB to debug the program, I get:

(gdb) info locals
c1_loc = 97 'a'
i_loc = 1
c2_loc = 98 'b'
d_loc = 2
c3_loc = 99 'c'
f_loc = 3
c4_loc = 100 'd'
s_loc = 4

I don't know how GDB get the name of the local variables, hope someone could help me.