Re: [PATCH 1/1] gdb: Avoid warning for the jump command inside an inline function.

[Bruno Larsen <blarsen@redhat.com>]

On 17/03/2023 13:56, Willgerodt, Felix wrote:
>> -----Original Message-----
>> From: Bruno Larsen <blarsen@redhat.com>
>> Sent: Freitag, 17. März 2023 11:14
>> To: Willgerodt, Felix <felix.willgerodt@intel.com>; gdb-
>> patches@sourceware.org
>> Cc: Cristian Sandu <cristian.sandu@intel.com>
>> Subject: Re: [PATCH 1/1] gdb: Avoid warning for the jump command inside
>> an inline function.
>>
>> On 24/01/2023 16:19, Felix Willgerodt via Gdb-patches wrote:
>>> When stopped inside an inline function, trying to jump to a different line
>>> of the same function currently results in a warning about jumping to
>> another
>>> function.  Fix this by taking inline functions into account.
>>>
>>> Before:
>>>     Breakpoint 1, function_inline (x=510) at jump-inline.cpp:22
>>>     22        a = a + x;             /* inline-funct */
>>>     (gdb) j 21
>>>     Line 21 is not in `function_inline(int)'.  Jump anyway? (y or n)
>>>
>>> After:
>>>     Breakpoint 2, function_inline (x=510) at jump-inline.cpp:22
>>>     22        a = a + x;            /* inline-funct */
>>>     (gdb) j 21
>>>     Continuing at 0x400679.
>>>
>>>     Breakpoint 1, function_inline (x=510) at jump-inline.cpp:21
>>>     21        a += 1020 + a;                /* increment-funct */
>>>
>>> This was regression-tested on X86-64 Linux.
>>>
>>> Co-Authored-by: Cristian Sandu <cristian.sandu@intel.com>
>>> ---
>>>    gdb/infcmd.c                           |  3 +-
>>>    gdb/testsuite/gdb.base/jump-inline.c   | 30 +++++++++++++++++
>>>    gdb/testsuite/gdb.base/jump-inline.exp | 45
>> ++++++++++++++++++++++++++
>>>    3 files changed, 77 insertions(+), 1 deletion(-)
>>>    create mode 100644 gdb/testsuite/gdb.base/jump-inline.c
>>>    create mode 100644 gdb/testsuite/gdb.base/jump-inline.exp
>>>
>>> diff --git a/gdb/infcmd.c b/gdb/infcmd.c
>>> index fd88b8ca328..40414bc9260 100644
>>> --- a/gdb/infcmd.c
>>> +++ b/gdb/infcmd.c
>>> @@ -1091,7 +1091,8 @@ jump_command (const char *arg, int from_tty)
>>>
>>>      /* See if we are trying to jump to another function.  */
>>>      fn = get_frame_function (get_current_frame ());
>>> -  sfn = find_pc_function (sal.pc);
>>> +  sfn = find_pc_sect_containing_function (sal.pc,
>>> +					  find_pc_mapped_section (sal.pc));
>> Hi Felix,
>>
>> Thanks for doing this, it is a good improvement, but I don't know if
>> this is the best way to go about it. Is there a reason why
>> find_pc_function should not return inlined functions?
>>
>> I feel like most of the time we want to know the function, knowing if
>> we're in an inlined one would be desirable, but I might be wrong. Does
>> anyone know?
>>
> Hi Bruno,
>
> I don't know the details, but the comments in symtab.h are rather explicit
> about it, so I assume there is a reason:
>
>
> /* lookup the function symbol corresponding to the address.  The
>     return value will not be an inlined function; the containing
>     function will be returned instead.  */
>
> extern struct symbol *find_pc_function (CORE_ADDR);
>
> /* lookup the function symbol corresponding to the address and
>     section.  The return value will be the closest enclosing function,
>     which might be an inline function.  */
>
> extern struct symbol *find_pc_sect_containing_function
>    (CORE_ADDR pc, struct obj_section *section);

Hi Felix,

I thought it was mostly a descriptive comment, rather than prescriptive. 
I tested changing find_pc_function locally and there were only 2 
regressions, which might just be broken assumptions, but our testsuite 
is probably not very comprehensive on inlined functions, so I don't know 
how representative this test actually is.

-- 
Cheers,
Bruno

>
> Thanks,
> Felix
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