Get argument names of functions in GDB without hitting a breakpoint - gdb

Question

I'm using mingw's GDB.
When I hit a breakpoint, it gives me the argument names for the function from debug symbols:
Breakpoint 1, CApp::OnTextInput (this=0x81ab888, ch=97)
However, I can't find a way to get argument names for functions that I haven't set a breakpoint on. With info functions, I can get argument types and function names, but not argument names.
Is it possible or do I always have to hit a breakpoint to get argument names?

Answer 1

I could not find how to do it with gdb, but you can do it with other tools: dwarfdump or objdump. For this simple program:
int main(int argc, char * argv[])
{
return 0;
}
you can dump dwarf debug info with dwarfdump:
$ dwarfdump a.out | grep -A30 "DW_AT_name.*main"
DW_AT_name main
DW_AT_decl_file 0x00000001 /tmp/1.c
DW_AT_decl_line 0x00000001
DW_AT_decl_column 0x00000005
DW_AT_prototyped yes(1)
DW_AT_type <0x0000006e>
DW_AT_low_pc 0x00401106
DW_AT_high_pc <offset-from-lowpc>18
DW_AT_frame_base len 0x0001: 9c: DW_OP_call_frame_cfa
DW_AT_GNU_all_call_sites yes(1)
DW_AT_sibling <0x0000006e>
< 2><0x0000004f> DW_TAG_formal_parameter
DW_AT_name argc
DW_AT_decl_file 0x00000001 /tmp/1.c
DW_AT_decl_line 0x00000001
DW_AT_decl_column 0x0000000e
DW_AT_type <0x0000006e>
DW_AT_location len 0x0002: 916c: DW_OP_fbreg -20
< 2><0x0000005e> DW_TAG_formal_parameter
DW_AT_name argv
DW_AT_decl_file 0x00000001 /tmp/1.c
DW_AT_decl_line 0x00000001
DW_AT_decl_column 0x0000001b
DW_AT_type <0x00000075>
DW_AT_location len 0x0002: 9160: DW_OP_fbreg -32
< 1><0x0000006e> DW_TAG_base_type
DW_AT_byte_size 0x00000004
DW_AT_encoding DW_ATE_signed
DW_AT_name int
< 1><0x00000075> DW_TAG_pointer_type
DW_AT_byte_size 0x00000008
There you can see that function main has 2 parameters with names argc and argv.
You can also use objdump to get the same information. Here is relevant output for main and it's parameters from objdump --dwarf=info a.out output:
<1><2d>: Abbrev Number: 2 (DW_TAG_subprogram)
<2e> DW_AT_external : 1
<2e> DW_AT_name : (indirect string, offset: 0x58): main
<32> DW_AT_decl_file : 1
<33> DW_AT_decl_line : 1
<34> DW_AT_decl_column : 5
<35> DW_AT_prototyped : 1
<35> DW_AT_type : <0x6e>
<39> DW_AT_low_pc : 0x401106
<41> DW_AT_high_pc : 0x12
<49> DW_AT_frame_base : 1 byte block: 9c (DW_OP_call_frame_cfa)
<4b> DW_AT_GNU_all_call_sites: 1
<4b> DW_AT_sibling : <0x6e>
<2><4f>: Abbrev Number: 3 (DW_TAG_formal_parameter)
<50> DW_AT_name : (indirect string, offset: 0x5): argc
<54> DW_AT_decl_file : 1
<55> DW_AT_decl_line : 1
<56> DW_AT_decl_column : 14
<57> DW_AT_type : <0x6e>
<5b> DW_AT_location : 2 byte block: 91 6c (DW_OP_fbreg: -20)
<2><5e>: Abbrev Number: 3 (DW_TAG_formal_parameter)
<5f> DW_AT_name : (indirect string, offset: 0x0): argv
<63> DW_AT_decl_file : 1
<64> DW_AT_decl_line : 1
<65> DW_AT_decl_column : 27
<66> DW_AT_type : <0x75>
<6a> DW_AT_location : 2 byte block: 91 60 (DW_OP_fbreg: -32)
<2><6d>: Abbrev Number: 0