From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from eggs.gnu.org (eggs.gnu.org [IPv6:2001:470:142:3::10]) by sourceware.org (Postfix) with ESMTPS id F05F2385E445 for ; Fri, 15 Mar 2024 21:11:51 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org F05F2385E445 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=gnu.org Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=gnu.org ARC-Filter: OpenARC Filter v1.0.0 sourceware.org F05F2385E445 Authentication-Results: server2.sourceware.org; arc=none smtp.remote-ip=2001:470:142:3::10 ARC-Seal: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1710537122; cv=none; b=wBspuh7wCyAFJ6RfP1Otj7KQwOzX4PxJCTHEAjl+MeR+hPAq7YEqQT79ce7BwE7zBeyI7Q3d45dLBpFwLDK/Tiuf0YiV1ICaj3YWnunBGPrqMcKaYLYMWygzsErcMRrUkCBNBw4u+p5hn5TcdHXuf99rlXyyBmKCjkc7znkHWJM= ARC-Message-Signature: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1710537122; c=relaxed/simple; bh=kZPAk56VSvYX4CVG1J4fACqe3IBIrRUlEr663JwKaXI=; 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7d1HyrPeeVhvS07EXhKquaV8dhUAuhAUhkKXl362b0GxzNhh8kbqvI/oh5qQ69kyDLyY0+EavyuK1 mURDOQ8VLta9YrbOQ==; Message-ID: <3b4f943d23543da2ba96dad8c81fa8c495fffd08.camel@gnu.org> Subject: Re: GDB 13.2: breakpoint at wrong line after unrelated change From: Paul Smith Reply-To: psmith@gnu.org To: Simon Marchi , gdb@sourceware.org Date: Fri, 15 Mar 2024 17:11:48 -0400 In-Reply-To: <06c7a0d1-6ba7-440a-a21a-616ed05cb5b0@simark.ca> References: <7c064cc544bfe453a250ca58b4d5ebd97919178d.camel@gnu.org> <4c3f986c-a562-4506-b382-c754678abcff@simark.ca> <7fcf12fbd4a106af488168d0e740e0d8ca9b3022.camel@gnu.org> <06c7a0d1-6ba7-440a-a21a-616ed05cb5b0@simark.ca> Autocrypt: addr=psmith@gnu.org; prefer-encrypt=mutual; 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 Organization: GNU's Not UNIX! Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.4 (by Flathub.org) MIME-Version: 1.0 X-Spam-Status: No, score=-0.3 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,SPF_HELO_PASS,SPF_PASS,TXREP,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On Mon, 2024-03-11 at 15:50 -0400, Simon Marchi wrote: > Ok, so clearly GDB failed to analyze the prologue.=C2=A0 Which is weird > because the two functions are identical (modulo the addresses).=C2=A0 To > get to the bottom of this, you (or someone else) would need to debug > GDB itself.=C2=A0 If you want to do this, I would start at function > skip_prologue_using_sal, in symtab.c.=C2=A0 Off hand, I don't think we > have a debug switch to enable logging for prologue skipping.=C2=A0 It > would be useful to have some here, as we would be able to compare the > logging shown in both cases. FYI I have finally gotten back to looking at this. I've only been at it for a short time but just for information: I was able to build GDB 14.2 (latest release) from source and I still see the issue there. So I started debugging. I can tell you that in the "good" binary case I can see that amd64_tdep.c:amd64_skip_prologue() is invoked which invokes symtab.c:skip_prologue_using_sal() as you suggested. In fact, these methods are called numerous times. In the "bad" binary case, neither of those methods is called, ever. I put a gdb_printf() in both functions and in the "good" binary I see probably 20 invocations between starting, setting the breakpoint, running, and exiting: in the "bad" binary zero invocations. I do see that we definitely invoke set_gdbarch_skip_prologue() with the amd64 function pointer in both cases, so it's not that. I'm looking to see where *_skip_prologue() is called from to figure out where the code paths diverge, just thought I'd send a note to let folks know that I've not dropped this investigation.