Why IDA Pro will generate this kind of code(mess up macro name and variable name)?

Question

I use IDA Pro 6.1 to disassembly ELF file, which is compiled on 32 bit Linux, gcc 4.6.3

I modified the code and try to make it reassemble, and I find a problem here(this is directly created by IDA Pro):

main    proc near
......
mov     dword ptr [esp+4], offset msgid
......
......
foo     proc near
msgid   =  dword ptr -18d
......
mov     [esp+1Ch+msgid], 1

section .rodata
msgid           db 'extra operand %s',0

So if I do some modify work and assembly it use nasm, it will produce this error:

error: label or instruction expected at start of line 

targeting on this line:

msgid           db 'extra operand %s',0

If I modify it like this:

main    proc near
......
mov     dword ptr [esp+4], offset msgid111
......
......
foo     proc near
msgid   =  dword ptr -18d
......
mov     [esp+1Ch+msgid], 1

section .rodata
msgid111           db 'extra operand %s',0

Then no error in this part.

So my questions are:

1. Why IDA Pro will use variable name as the macro name?
2. Is there any better way to bypass this error than modify the variable name?

Thank you!

Answer 1

1. IDA will use this variable name if you renamed it somehow. This variable name is local for the function because it is a stack offset.

2. There is no better way than name modification. You can solve this specific kind of error by writing script that renames anything in .rodata section by applying g_ prefix to any object in it.

The code will look like this:

#Use carefully, I didn't check this code
#beware errors

import idautils
import idc

prefixes = {".rodata": "g_ro_",
            ".data": "g_"}

#Passing over all non default names
for (ea, name) in idautils.Names():
    seg_name = idc.SegName(ea)
    # if the name is in required segment
    if seg_name in prefixes:
        if not name.startswith(prefixes[seg_name]):
            # renaming it by adding required prefix
            # if the prefix is not added yet
            name = prefixes[seg_name] + name
            idc.MakeName(ea, name)