LLDB does not load debug symbols on Windows 10

[llvmbot]

Bugzilla Link	46613
Version	10.0
OS	Windows NT
Reporter	LLVM Bugzilla Contributor
CC	@amccarth-google,@dwblaikie,@jaro-sevcik,@JDevlieghere

Extended Description

Trying to explore a full LLVM toolchain for my C/C++ development on Windows, and found that LLDB cannot load debug symbols on Windows 10. LLDB is producing .PDB and .ILK files for the executable I want to debug, but when LLDB loads the executable, no debug symbols are loaded.

Issues I experienced that lead me to realize the symbols weren't being loaded:

• Could not set breakpoints (LLDB reported "Unable to resolve breakpoint to any actual location").
• Could not see source listing (LLDB command 'source list' did not output anything).

Attempted fixes:

• I tried rolling back to LLVM 6.0, to see if the issue was isolated to LLVM 10.0. Found that the issue persisted. I got curious and installed LLVM 10 and LLVM 6 on my WSL terminal and found that both the 10.0 LLDB and the 6.0 LLDB worked as expected, so I can only assume the issue is isolated to Windows.
• Tried passing -gdwarf and -glldb to the Windows version of clang, but LLDB was still not able to load debug symbols.

There is a duplicate of this bug (#42160) dating little more than year old (posted 2019-06-06) that has reported this issue but didn't receive any attention.

Questions:

• Is there anyone available to work on this? If not, I would gladly help out.
• Is there any way to get verbose logging from LLDB? That would greatly help me troubleshoot the source of the issue.

[llvmbot]

Thanks for the input.

Greg, when I tried the fix recommended by 46158, the problem persisted. Though vcvarsall.bat wasn't mentioned in 46158, I tried that as well and it didn't improve my situation. This was all with 10.0 LLDB, and testing on both PowerShell and CMD.

Jaroslav, linking with lld and using DWARF symbols worked, so in the mean-time there's at least a workaround.

Another issue I noticed was that the --debug flag for LLDB didn't offer any more detail into what was happening than running LLDB without --debug (output was the same). Is there a reason for that?

[jaro-sevcik]

That said, DWARF debug info should work fine on Windows as long as you link with lld.

C:\Projects\temp>type a.cc

include

int main(int argc, char **argv) { printf("Hello\n"); return 0; }

C:\Projects\temp>clang -gdwarf -O0 -c a.cc -o a.o

C:\Projects\temp>clang -gdwarf -fuse-ld=lld a.o -o a.exe

C:\Projects\temp>lldb a.exe (lldb) target create "a.exe" Current executable set to 'C:\Projects\temp\a.exe' (x86_64). (lldb) b main Breakpoint 1: where = a.exe`main + 21 at a.cc:4:3, address = 0x0000000140001015 (lldb) r Process 24592 launched: 'C:\Projects\temp\a.exe' (x86_64) Process 24592 stopped

• thread #​1, stop reason = breakpoint 1.1 frame #​0: 0x00007ff77bcf1015 a.exe`main(argc=1, argv=0x000002cadff88400) at a.cc:4:3 1 #include 2 3 int main(int argc, char **argv) { -> 4 printf("Hello\n"); 5 return 0; 6 } (lldb) p argc (int) $0 = 1 (lldb)

[amccarth-google]

I'm working on a but in which an explicit target symbols add my.pdb command doesn't work, but that's for reasons specific to that code path. If LLDB can find your PDB when the target is created, it should work because that's a completely different code path which doesn't have the checks that fail from when you attempt the explicit interactive command. Sigh.

Someday, we need to consolidate a bunch of code paths through LLDB. It would be really nice if the interactive commands and the corresponding SB entry points merged much sooner.

[llvmbot]

I should rephrase "not well implemented". I meant to say "it would be nice if this would work out of the box" or "LLDB should give the user feedback on why PDB symbols are not being loaded".

[llvmbot]

The current situation is not well implemented. I believe on windows you must run the Visual Studio compiler setup batch file to setup some environment variables so that LLDB can find and load the PDB DLL file so it can load symbols using the Microsoft PDB parsing DLL. See:

llvm/llvm-bugzilla-archive#46158

Let us know if any of the information in that bug helps. If it does, please mark this as a duplicate of 46158

[Traveller23]

When I execute target symbols add my_executable.pdb, lldb (v16.0.3) shows "error: symbol file 'path\to\my_executable.pdb' does not match any existing module".

$ lldb my_executable.exe
(lldb) target create "my_executable.exe"
Current executable set to '***\cmake-build-debug\bin\my_executable.exe' (x86_64).
target symbols add my_executable.pdb
(lldb) target symbols add my_executable.pdb
error: symbol file '***\cmake-build-debug\bin\my_executable.pdb' does not match any existing module

[obiwan87]

Use the visual studio developer prompt and there set the following environment variable using

set LLDB_USE_NATIVE_PDB_READER=yes