Debugging Sumatra

Help us debug Sumatra hangs or crashes

If Sumatra crashes or hangs reliably on your machine but we can’t reproduce it ourselves, you can help us by debugging it. Here’s a tutorial on how to do it.

Please first test with latest pre-release version from https://www.sumatrapdfreader.org/prerelease.html

Some bugs might already be fixed there compared to latest

Those instructions require SumatraPDF 3.2 or later.

Getting logs #

We log information that might be helpful in diagnosing issues.

To see the logs: Ctrl + K (Command Palette), type show log

This saves logs to a file and opens default editor for .txt files with log file.

Install necessary software #

Install WinDBG debugger from Microsoft Store at https://www.microsoft.com/en-us/p/windbg-preview/9pgjgd53tn86#activetab=pivot:overviewtab. Alternatively, you can follow instructions from https://docs.microsoft.com/en-us/windows-hardware/drivers/debugger/debugger-download-tools
In SumatraPDF, use menu Debug / Download symbols. Symbols are important for the debugger (like WinDBG) to resolve addresses to names that

First, vocabulary. %ProgramFiles% means the standard directory where Windows installs programs. It’s c:\Program Files on 32-bit Windows and c:\Program Files (x86) on 64-bit Windows.

Debugging a crash #

To debug crashes:

start SumatraPDF.exe under the control of WinDBG
- start WinDBG.exe
- File/Open (Ctrl-E), find and open SumatraPDF.exe executable
- In WinDBG, type:
  - .sympath+ SRV*c:\symbols*https://msdl.microsoft.com/download/symbols
  - g
when Sumatra crashes, type: !analyze -v and paste the result of that to the bug report

Debugging a hang #

Here are the steps to follow if Sumatra hangs

Start SumatraPDF.exe and get it to hang
start WinDBG.exe
use File/Attach to process (F6) and select SumatraPDF.exe from the
In WinDBG, type:

7.1) .sympath+ SRV*c:\symbols*https://msdl.microsoft.com/download/symbols

7.2) ~*kb

7.3) lmf

Attach the output to bug report.