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digitalmars.D.ldc - Debugging with LLDB on Windows

reply WebFreak001 <d.forum webfreak.org> writes:
I'm trying to use LLDB on Windows to debug a program compiled 
with LDC, however it seems LLDB doesn't load any debug symbols or 
it doesn't know how to parse the ones emitted by LDC.

Is there some way to make LDC emit debug symbols parsable by 
LLDB? I believe it needs DWARF debugging information to work 
properly, but I assume that's what LDC already emits.

On the other hand I'm also not sure if it's just the LLDB build 
I'm using, I've obtained it from the VSCode extension 
https://github.com/vadimcn/vscode-lldb and it says the version is

lldb version 10.0.1 (local revision 
a55a07af20ef3228dfc31bd5c0c0161c356fb1af)
   clang revision a55a07af20ef3228dfc31bd5c0c0161c356fb1af
   llvm revision a55a07af20ef3228dfc31bd5c0c0161c356fb1af
   rust-enabled
Aug 03 2020
parent reply kinke <noone nowhere.com> writes:
On Monday, 3 August 2020 at 11:56:30 UTC, WebFreak001 wrote:

 I believe it needs DWARF debugging information to work 
 properly, but I assume that's what LDC already emits.


It doesn't, see 
https://forum.dlang.org/post/ttblgcwiwmdhyukzpocb forum.dlang.org. - Wrt.
VSCode on Windows, we've re-activated `-gc` to improve debugging with the
Microsoft C/C++ plugin, see https://github.com/ldc-developers/ldc/pull/2869.
Aug 03 2020
parent reply WebFreak001 <d.forum webfreak.org> writes:
On Monday, 3 August 2020 at 17:43:21 UTC, kinke wrote:

 On Monday, 3 August 2020 at 11:56:30 UTC, WebFreak001 wrote:

 I believe it needs DWARF debugging information to work 
 properly, but I assume that's what LDC already emits.


 It doesn't, see 
 https://forum.dlang.org/post/ttblgcwiwmdhyukzpocb forum.dlang.org. - Wrt.
VSCode on Windows, we've re-activated `-gc` to improve debugging with the
Microsoft C/C++ plugin, see https://github.com/ldc-developers/ldc/pull/2869.


is it possible to then simply target the MinGW triple? Are there 
any disadvantages coming from it?

I would like to try making a small D script for LLDB so it can 
parse all the types and hopefully make a good debug experience on 
all platforms consistently, because LLDB implements DWARF debug 
symbols on all platforms.
Aug 03 2020
parent reply kinke <noone nowhere.com> writes:
On Monday, 3 August 2020 at 20:37:49 UTC, WebFreak001 wrote:

 is it possible to then simply target the MinGW triple?


Nope, not (fully) supported by druntime and Phobos, and the 
compiler would probably require a few adaptations too.

As you're the 2nd guy asking for DWARF debuginfos and MSVC 
targets in a month, and LLVM supports it: 
https://github.com/ldc-developers/ldc/pull/3533
Aug 04 2020
parent reply Siemargl <inqnone gmail.com> writes:
On Tuesday, 4 August 2020 at 18:44:02 UTC, kinke wrote:

 On Monday, 3 August 2020 at 20:37:49 UTC, WebFreak001 wrote:

 is it possible to then simply target the MinGW triple?


 Nope, not (fully) supported by druntime and Phobos, and the 
 compiler would probably require a few adaptations too.

 As you're the 2nd guy asking for DWARF debuginfos and MSVC 
 targets in a month, and LLVM supports it: 
 https://github.com/ldc-developers/ldc/pull/3533


Some problems with llvm debugging.

Test log from lldb 10.0.0 - not recognized main function name 
(but other is found), not steps next line (expect goto finally 
expression) after throw exception.

Compile>ldc2 -gdwarf -gc -m64 except.d
lld-link: warning: section name .debug_abbrev is longer than 8 
characters and will use a non-standard string table
lld-link: warning: section name .debug_info is longer than 8 
characters and will use a non-standard string table
lld-link: warning: section name .debug_line is longer than 8 
characters and will use a non-standard string table
lld-link: warning: section name .debug_loc is longer than 8 
characters and will use a non-standard string table
lld-link: warning: section name .debug_pubnames is longer than 8 
characters and will use a non-standard string table
lld-link: warning: section name .debug_pubtypes is longer than 8 
characters and will use a non-standard string table
lld-link: warning: section name .debug_ranges is longer than 8 
characters and will use a non-standard string table
lld-link: warning: section name .debug_str is longer than 8 
characters and will use a non-standard string table

Used MSVC Build tools 2019 (as -v option tells), but lld-link.

-----

E:\_bin\LLVM\bin\lldb.exe except.exe
 
                                                 (lldb) target
create "except.exe"


Current executable set to 
'E:\VSProjects\testjunk\DbetterC\except.exe' (x86_64).
(lldb) b main
Breakpoint 1: no locations (pending).
WARNING:  Unable to resolve breakpoint to any actual locations.
(lldb) b _Dmain
Breakpoint 2: no locations (pending).
WARNING:  Unable to resolve breakpoint to any actual locations.
(lldb) b except.d:3
Breakpoint 3: where = except.exe`_Dmain + 16 at except.d:9:13, 
address = 0x0000000140001010
(lldb) r
Process 90056 launched: 
'E:\VSProjects\testjunk\DbetterC\except.exe' (x86_64)
Process 90056 stopped


except.d:9:13
    6        {
    7            try
    8            {
-> 9                throw new Exception("first");
    10           }
    11           finally
    12           {
(lldb) n
Process 90056 exited with status = 0 (0x00000000)
(lldb)
---
Feb 17 2021
parent reply Siemargl <inqnone gmail.com> writes:
On Wednesday, 17 February 2021 at 20:26:54 UTC, Siemargl wrote:

 Some problems with llvm debugging.

 Test log from lldb 10.0.0 - not recognized main function name 
 (but other is found), not steps next line (expect goto finally 
 expression) after throw exception.


Something wrong with generation debug info.

Case 1. CV debug info


ldc2 -g -gc except.d
list - showed nothing
b _Dmain - works, breakpoink stopped, but shows only assembly 
code
list - showed nothing after stop
b except.d:13  - not working (no source code)
b _d_throw_exception - also works as asm
image dump symtab except.exe - works, many D symbols seen (>1000)


Same executable, MS WinDbg X64 works, may set breakpoints in 
opened source code, step by step debugging works.
Also Windbg commands worked fine bp Dmain, bp d_throw_exception 
working (without leading underscore!)


Case 2. Dwarf debug info


ldc2 -gdwarf -g -gc except.d
b _Dmain - not working
b except.d:13  - works, after stoping at breakpoint shows 
source, 'next' command steps ok
list - showed source ater breakpoint stops
b _d_throw_exception - not working
image dump symtab except.exe - not works, num_symbols = 0
Feb 23 2021
parent kinke <noone nowhere.com> writes:
On Tuesday, 23 February 2021 at 12:03:05 UTC, Siemargl wrote:

 Same executable, MS WinDbg X64 works, may set breakpoints in 
 opened source code, step by step debugging works.
 Also Windbg commands worked fine bp Dmain, bp d_throw_exception 
 working (without leading underscore!)


The generated CodeView has been checked/tailored for the VS 
debugger (with both -g and -gc). The corresponding tests use the 
`cdb` console debugger. I've noted some discrepancies between VS 
and cdb too.

I haven't tested DWARF on Windows at all, and neither fired up 
lldb a single time on Windows. I have no idea about its Windows 
support. You could try `--debugger-tune=lldb` (a pure LLVM 
option, doesn't affect LDC at all) and see if that improves 
anything.
Feb 23 2021