[tcf-dev] line numbers / unit_line_to_address

[Samuel Ghinet <samuel.ghinet@xxxxxxxxxxxx>]

Hello,

I am working on a debugger using tcf. I have ran into a problem with the 
line to address functionality when the compiler that build the 
executable provides the column numbers.

The tcf agent has checks like this (as seen in linenumbers_elf.c, 
function "unit_line_to_address"):

> else if (state->mFile > file || state->mLine > line || (state->mLine 
== line && state->mColumn > column)) {
...
> if (next_line < line || (next_line == line && next_column <= column)) {
...
> if (next_line > line || (next_line == line && next_column > column)) {
...
if (state->mColumn > column) break;


In the source code for my file, line 40, I have the column 5 (the 
beginning of the c++ instruction at that line).
However, when I am trying to add a breakpoint from Eclipse to that line, 
Eclipse requests line 40 and column 0. This results in the fact that tcf 
checks line 40 and sees that the column of that line (from 
LineNumbersState) is 5 while the requested column is 0, and so it 
considers that line 40 is not what I want - when I asked for line 40.

I have read from a dwarf document (says the same in both version 2 and 
version 4 I looked in), describing "column":
> An unsigned integer indicating a column number within a source line. 
Columns are numbered beginning at 1. The value 0 is reserved to indicate 
that a statement begins at the “left edge” of the line.

I am not sure how to understand "left edge" of the line, but it appears 
that the first column for a c++ statement sitting on the very left of 
the page(so that there is no space / tab before that statement) is 1. I 
am assuming that, when Eclipse asks for "column 0", it actually says "I 
don't care what column is, I'm only interested in the line"

What should I do to make the line information be retrieved correctly, 
when the request comes from Eclipse, and the compiler I build the 
project with gives me the column numbers?

Could you please help me?

Thanks,
Samuel Ghinet