Re: [RFC] breakpoints and function prologues...

[Michael Snyder <msnyder@redhat.com>]

Jim Blandy wrote:
> 
> For as long as I can remember, GDB has treated setting a breakpoint on
> the line containing the opening curly brace of a function's block as
> meaning `set a breakpoint before the prologue'.  I've always assumed
> that was deliberate behavior.

Semi.  It follows from the line symbols.  GCC emits a line symbol
for that line which spans the address range of the prologue.  So
you could say it's deliberate -- but on GCC's part, rather than
on GDB's.

> But I can't find it documented in the GDB manual. 

That's because it's not a special case.  It's the same
behavior as for any line -- put the breakpoint where 
the compiler says to.

> And it's a lousy
> user interface (`break *main' works just as well, and makes more sense
> to me).  Maybe the behavior is just a side effect of the decision to
> attribute the prologue code to the line containing the opening curly
> brace 

Exactly -- 

> --- if the program stops in the prologue, that's as sensible a
> place as any to claim it's at.
> 
> So I'd support changing `break LINENO' to always skip the prologue.

I would not.  It's changing a behavior that people have 
become accustomed to.