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([2804:14d:8084:9a69::1002]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6e65d9f31fdsm23016236d6.69.2025.02.14.09.53.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 14 Feb 2025 09:53:28 -0800 (PST) Message-ID: <7810dcf9-5f59-4fad-9352-e9d5dcb98f10@redhat.com> Date: Fri, 14 Feb 2025 14:53:26 -0300 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: Follow up to stabs deprecation - AIX regressions To: Simon Marchi , Kevin Buettner Cc: gdb-patches@sourceware.org References: <20250213094829.2b6f73d5@f41-zbm-amd> <54acfac1-ac30-4012-9a64-8b3070338b11@redhat.com> <20250213104321.71331304@f41-zbm-amd> <35754735-34f5-4aca-99e4-3862f8cde5b9@simark.ca> From: Guinevere Larsen In-Reply-To: <35754735-34f5-4aca-99e4-3862f8cde5b9@simark.ca> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: sFA9dvX_5uUoQm98c20fTInWJ8f019I3tcJcWnxN6Lw_1739555609 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: gdb-patches-bounces~public-inbox=simark.ca@sourceware.org On 2/13/25 5:21 PM, Simon Marchi wrote: > > On 2025-02-13 12:58, Guinevere Larsen wrote: >> On 2/13/25 2:43 PM, Kevin Buettner wrote: >>> On Thu, 13 Feb 2025 14:21:01 -0300 >>> Guinevere Larsen wrote: >>> >>>> On 2/13/25 1:48 PM, Kevin Buettner wrote: >>>>> On Thu, 13 Feb 2025 09:25:44 -0300 >>>>> Guinevere Larsen wrote: >>>>> >>>>>> * DWARF reading can sometimes fail in AIX. Currently, reading dwarf for >>>>>> xcoff inferiors is called on it's own, with no warning if dwarf fails >>>>>> (which probably makes sense, considering the default format in aix is >>>>>> still stabs). I added a warning when failing to read dwarf and noticed >>>>>> it being triggered on inferiors compiled with -gdwarf >>>>> I assume that you mean that stabs is the default when compiling with >>>>> gcc. Is stabs still also the default format for XLC (IBM Open XL C/C++) ? >>>> Yes, sorry, I meant gcc. The compile farm had versions 10 and 12, both >>>> with the same behavior. >>>> >>>> I don't think the compile farm has XLC compilers available for testing, >>>> or if they do I don't know how to use it, so I couldn't tell you... >>> I think it'd be good to find out XLC's preferred debug format. If it >>> uses/prefers DWARF, that'd be a good argument for gcc (on AIX) >>> switching to DWARF for it's preferred format too. >>> >>> Kevin >>> >> I just looked over at the GCC releases, and the GCC12 changelog says the following: >> >> * *STABS:* Support for emitting the STABS debugging format is deprecated and will be removed in the next release. All ports now default to emit DWARF (version 2 or later) debugging info or are obsoleted. >> >> Since the default is supposed to have changed *in* gcc 12 - which is the version that AIX has - or the port be obsolete, it looks to me like that gcc on AIX is obsoleted... >> >> In other words, gcc already knows it should change but seems to have given up on AIX? > Given this commit (present in gcc 11): > > https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=56b5d13e27891ed1caec07826a07bb2e0621f914 > > I would expect gcc 12 to produce DWARF by default, I'm not sure why you > don't see that. > > Simon > This is kind of weird... This is a bit of a side diversion, though. The original thing Kevin pointed out was whether GDB not reporting that DWARF reading failed was related to stabs being the default. I just double checked, and I don't think it is. elfread reads dwarf in an if condition, but doesn't do anything with the result (no matter if it is positive or negative). coffread does the same I think the idea is that maybe the objfile being read may have not been compiled with debug symbols in the first place, so warning about it is redundant, especially considering that for now, all supported objfiles will have at least minsyms available. That will change with removing stabs in xcoff, which is why I highlighted that it can fail even with existing dwarf in the inferior. It not being reported is the default, but is why this has gone unnoticed. -- Cheers, Guinevere Larsen She/Her/Hers