On Mon, Dec 17, 2007 at 11:11:46PM -0200, Alexandre Oliva wrote:
> Line number information has a well-defined meaning: it ought to
> represent the source code line that best represents the source-code
> construct that ended up implemented using that instruction.
You implicitly assume that souch a source code line exists.
Consider something like
int func(bool cond, int a, int b, int c)
{
int out;
if (cond)
out = a + b;
else
out = a + b + c;
return out;
}
The optimizer might produce something that structurally resembles
out = a + b;
if (!cond)
out += c;
return out;
If you set a breakpoint on the addition of a and b, it will trigger
regardless of the value of cond. Furthermore, there isn't a place
to put a breakpoint that will trigger only for the case where cond
is true, as you can on unoptimized code. So you need to choose
between natural debugging and optimization.
