[lldb-dev] Line number resolution problem

[Greg Clayton]

Great! Just know the debugger always uses exactly what the compiler gives us so using "dwarfdump --debug-line -e <dwarffile>" will always show you what the compiler is giving us. 

You can also inspect your target to see the line tables with the new "tk" support. LLDB top of tree has a script "lldb/examples/python/lldbtk.py" that adds a bunch of "tk" prefixed commands including "tk-target" to inspect your target:

(lldb) command script import lldb/examples/python/lldbtk.py
(lldb) file a.out
(lldb) tk-target

Then expand as shown and you will see all line table entries.

> On Oct 9, 2014, at 2:49 AM, Mario Zechner <badlogicgames at gmail.com> wrote:
> 
> Following up on this, the issue seems to be with LLVM's alwaysinline pass, which is the only pass we activate when compiling in debug mode. This LLVM IR http://pastebin.com/FM1BXJdX gets turned into this http://pastebin.com/g1Nv8PJL assembler code, with and without the pass. Turning off that pass can resolve the issue in terms of emitting the proper debug info in the assembler code.
> 
> Thanks for the help!
> 
> On Thu, Oct 9, 2014 at 10:57 AM, Mario Zechner <badlogicgames at gmail.com> wrote:
> Here's the dwarfdump: http://pastebin.com/4DyfLrtc
> 
> That tells me that there aren't any addresses associated with the missing lines.
> 
> They are in the LLVM IR http://pastebin.com/zBwtwPgh
> 
> But they are missing from the generated assembler code: http://pastebin.com/t6fvTXZU
> 
> My guess would be that we have some LLVM optimization turned on that eliminates the code for the missing lines. I'll investigate.
> 
> Thanks a lot for your help, really appreciate it. Sorry if i wasted your time.
> 
> On Wed, Oct 8, 2014 at 8:27 PM, Greg Clayton <gclayton at apple.com> wrote:
> Please attach the output of "dwarfdump --debug-line -e <FILE>". I can tell you more when I see that output.
> 
> Greg
> 
> > On Oct 8, 2014, at 5:10 AM, Mario Zechner <badlogicgames at gmail.com> wrote:
> >
> > Hi,
> >
> > i'm currently trying to track down the following issue. We create LLVM IR like this
> > compilation unit: JdwpThreads.java
> >    ; line 8
> >    %t16 = load %Object** %$r6, !dbg !{i32 8, i32 0, metadata !33, null}
> >     store %Object* %t16, %Object** %r4, !dbg !{i32 8, i32 0, metadata !33, null}
> >
> >     ; line 19
> >     call void @"llvm.dbg.declare"(metadata !{%Object** %r4}, metadata !38), !dbg !{i32 19, i32 0, metadata !34, null}
> >     %t17 = load %Object** %r4, !dbg !{i32 19, i32 0, metadata !34, null}
> >     call void @"[j]java.lang.Thread.start()V[Invokevirtual(com/robovm/debug/server/apps/JdwpThreads,java/lang/Thread)]"(%Env* %p0, %Object* %t17), !dbg !{i32 19, i32 0, metadata !34, null}
> >
> >     ; line 20
> >     %t18 = trunc i32 0 to i8, !dbg !{i32 20, i32 0, metadata !34, null}
> >     call void @"[j]com.robovm.debug.server.apps.JdwpThreads.stopped(Z)[set]"(%Env* %p0, i8 %t18), !dbg !{i32 20, i32 0, metadata !34, null}
> >
> >     ; line 21
> >     %t19 = load %Object** %r4, !dbg !{i32 21, i32 0, metadata !34, null}
> >     call void @"[j]java.lang.Thread.join()V[Invokevirtual(com/robovm/debug/server/apps/JdwpThreads,java/lang/Thread)]"(%Env* %p0, %Object* %t19), !dbg !{i32 21, i32 0, metadata !34, null}
> >
> > When setting a breakpoint for line 19 or 20 in that compilation unit, LLDB resolves it to line 21
> >
> > (lldb) br set -f JdwpThreads.java -l 19
> >
> > Breakpoint 1: where = JdwpThreadTest`[J]com.robovm.debug.server.apps.JdwpThreads.main([Ljava/lang/String;)V + 282 at JdwpThreads.java:21, address = 0x0028531f
> >
> > (lldb) br set -f JdwpThreads.java -l 20
> >
> > Breakpoint 2: where = JdwpThreadTest`[J]com.robovm.debug.server.apps.JdwpThreads.main([Ljava/lang/String;)V + 282 at JdwpThreads.java:21, address = 0x0028531f
> >
> >
> > The functions being called are all inlined functions. I suspected that to be the issue but don't know how to resolve it.
> >
> > I'm a bit puzzled as to why that is and would appreciate any pointers. I can provide a Mac OS X binary or a dwarfdump if required.
> >
> > Thanks,
> > Mario
> > _______________________________________________
> > lldb-dev mailing list
> > lldb-dev at cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev
> 
> 
> 

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