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Re: [PING][RFC][PATCH v2] Python API: add gdb.stack_may_be_invalid
- From: Pedro Alves <palves at redhat dot com>
- To: Martin Galvan <martin dot galvan at tallertechnologies dot com>, gdb-patches at sourceware dot org, Doug Evans <dje at google dot com>, Eli Zaretskii <eliz at gnu dot org>, Ulrich Weigand <uweigand at de dot ibm dot com>, Daniel Gutson <daniel dot gutson at tallertechnologies dot com>
- Date: Fri, 07 Nov 2014 17:09:30 +0000
- Subject: Re: [PING][RFC][PATCH v2] Python API: add gdb.stack_may_be_invalid
- Authentication-results: sourceware.org; auth=none
- References: <CAOKbPbZd+ppseGQW2OirBm4y5O=LgUMP-Pf8=RF00hnPOuMutw at mail dot gmail dot com>
On 11/07/2014 01:32 PM, Martin Galvan wrote:
> 2) The behavior of handle_step_into_function and setting breakpoints
> is inconsistent for optimized code, at least in ARM. If you step into
> a function in a program compiled with gcc -O1, you'll see the PC ends
> up one instruction after the set of instructions that place the
> arguments passed as registers in the registers they'll be used in. If
> you do "break myFunction", however, the breakpoint will correctly be
> placed at the very first instruction. Both handle_step.. and setting
> breakpoints have the same effect on -O0 code.
We should really fix this. I can't imagine we do this on purpose.
> If we look at how "break myFunction" works, we'll see that we end up
> calling find_function_start_sal to determine at which PC we have to
> place our breakpoint. Therefore, that's the function we should be
> calling when checking whether the stack frame will be valid at a
> prologue, as it also accounts for optimizations.
We expose functions and sals as python objects.
Shouldn't we instead consider exposing find_function_start_sal
in the function object? Or maybe symbol_to_sal in the Symbol object?
I can well imagine these being useful to other use cases.
Thanks,
Pedro Alves