Re: [PATCH] Fix gdb.cp/no-dmgl-verbose.exp test

[Pedro Alves <pedro@palves.net>]

On 2022-04-29 18:20, Pedro Alves wrote:
> On 2022-04-29 18:09, Keith Seitz wrote:
>> On 4/29/22 09:57, Pedro Alves wrote:
>>> On 2022-04-29 16:48, Carl Love via Gdb-patches wrote:
>>>> On Fri, 2022-04-29 at 09:14 +0000, Lancelot SIX wrote:
>>>
>>> So the file is called gdb.cp/no-dmgl-verbose.exp.  "no-dmgl" most certainly means "no demangle".
>>>
>>> How is that related to "no demangle verbose" ?  A mystery.
>>
>> I believe I remember some history of this...
>>
>> When I did the physname work years ago, a maintainer objected that the
>> recorded physname for a function which takes a std::string was
>> "reduced" to "std::string<blah blah blah>" instead of recording (and
>> thus subsequently printing) "std::string" like other tools do. [He
>> speciifcally mentioned "nm".]
>>
>> The "no-dmgl-verbose" refers to the demangler option, DMGL_VERBOSE,
>> which I originally used when computing physnames. I believe this test's
>> intention was to make sure that DMGL_VERBOSE didn't creep back into the
>> code.
>>
>> [Background: At the time, the compiler did not output sufficient debuginfo
>> for a bunch of symbols, such as ctors. Thus the physname computation
>> was a way to "fill-in" this missing/necessary information.]
>>
>> There's a number of other workarounds for this "std::string"
>> vs "std::string<blah blah blah>" (and others) in cp-support.c.
>> See "ignore_typedefs". [Pardon if my explanation is imprecise.
>> This was a looong time ago.]
> 
> Thanks Keith!
> 
> That leads to this:
> 
>  https://sourceware.org/pipermail/gdb-patches/2011-July/thread.html

Sigh, wrong url, obviously.  I meant, this:

 https://sourceware.org/pipermail/gdb-patches/2011-June/083081.html

Pedro Alves

> 
> The "Test loading symbols from unrelocated C++ object files." intro is found in
> 
>  gdb.cp/cp-relocate.exp:# Test loading symbols from unrelocated C++ object files.
> 
> so I guess that Jan copied that testcase, and didn't update the intro.  The "unrelocated"
> aspect seems like not important for the test.
> 
> Note how Jan says:
> 
> "After Keith's fix of GDB PR 12266 GDB should resolve mostly any form
> (typedefed/untypedefed etc.) of the user entered function parameters."
> 
> I believe that should be true today, and GDB should be able to set a breakpoint
> on the typedef'ed f(std::string), no?  I find it very hard to believe that Jan
> didn't notice that the
> 
>  gdb_breakpoint {'f(std::string)'}
> 
> call was failing back then.  From the message, it very much seems like it was
> passing back then.  And then, the other test:
> 
>  gdb_test {break 'f(std::basic_string<char, std::char_traits<char>, std::allocator<char> >)'} \
>  	 {Function ".*" not defined\.} \
>  	 "DMGL_VERBOSE-demangled f(std::string) is not defined"
> 
> means that "std::basic_string<char, std::char_traits<char>, std::allocator<char> >" is what
> you get when you demangle the function's linkage name with DMGL_VERBOSE, which is different
> from what you get if you demangle without DMGL_VERBOSE, and this test is thus making sure that
> such a demangled name is not defined.
> 
> The proposed change completely turns the testcase on its head.