Re: [PATCH v2] gdb: make "start" breakpoint inferior-specific

[Tom de Vries <tdevries@suse.de>]

On 11/14/22 14:19, Simon Marchi wrote:
> 
> 
> On 11/14/22 06:29, Tom de Vries wrote:
>> On 11/11/22 20:03, Simon Marchi via Gdb-patches wrote:
>>>> I'm not sure if this is a better solution: it's more intrusive.
>>> Ah, that would be good too.  We wouldn't have to bake in the knowledge
>>> of which languages use which operator.  But I'm also a bit scared of
>>> other unintended consequences when looking up the main symbol, as I see
>>> the current_language is involved in some places.  To be safe, I'll just
>>> go with my naive patch.  Thanks for the suggestion.
>>
>> FWIW, I've just stumbled onto language unknown, and realized that strictly speaking we've got a regression because we used to have:
>> ...
>> $ gdb -q -batch a.out -ex "set language unknown" -ex start
>> Temporary breakpoint 1 at 0x40050b: file /home/vries/hello.c, line 6.
>>
>> Temporary breakpoint 1, main () at /home/vries/hello.c:6
>> 6         printf ("hello\n");
>> Warning: the current language does not match this frame.
>> $
>> ...
>> but now we have:
>> ...
>> $ gdb -q -batch a.out -ex "set language unknown" -ex start
>> expression parsing not implemented for language "Unknown"
>> $
>> ...
>>
>> I don't really care about this, I thought I just mention it.
> 
> Huh...
> 
> What is "set language unknown" useful for, generally speaking?  If
> debugging something in a language GDB doesn't know about, I think it
> will fall back to minimal.  Could we just not expose the "unknown"
> language to the user?

Yeah, interestingly it also doesn't show up in the help:
...
$ gdb
(gdb) help set language
Set the current source language.
The currently understood settings are:

local or auto    Automatic setting based on source file
c                Use the C language
objective-c      Use the Objective-C language
c++              Use the C++ language
d                Use the D language
go               Use the Go language
fortran          Use the Fortran language
modula-2         Use the Modula-2 language
asm              Use the Assembly language
pascal           Use the Pascal language
opencl           Use the OpenCL C language
rust             Use the Rust language
minimal          Use the Minimal language
ada              Use the Ada language
...

Though that may have been an oversight, I'm not sure.

Looking through the testsuite, there are a few uses:
...
$ find gdb/testsuite/ -type f | xargs grep "set lang.*unknown"
gdb/testsuite/gdb.base/parse_number.exp:gdb_test_no_output "set language 
unknown"
gdb/testsuite/gdb.base/langs.exp:    gdb_test_no_output "set language 
unknown"
gdb/testsuite/gdb.base/default.exp:gdb_test "set language" "Requires an 
argument. Valid arguments are auto, local, unknown, ada, asm, c, c.., d, 
fortran, go, minimal, modula-2, objective-c, opencl, pascal, rust."
gdb/testsuite/gdb.cp/demangle.exp:    gdb_test_no_output "set language 
unknown"
...

But I think removing it from the set language command, and replacing it 
with "maint set language unknown" should be ok.

Thanks,
- Tom

Thanks,
- Tom