feat(crashpad): capture client & handler logs

[jpnurmi]

Capture crashpad's client- and handler-side log output separately in the run directory: <run>/crashpad-client.log via logging::InitLogging on the client side, and <run>/crashpad-handler.log via --log-file= on the handler side. Both files are cleaned up with the rest of the .run directory on the next sentry_init, so they don't bloat the database.

When debug is enabled, also OR in LOG_TO_STDERR on the client side (so crashpad's client-side logs also tee to the app's stderr) and forward the SDK's log level to the handler via --log-level=N so the handler's log file matches the configured verbosity. TRACE and DEBUG map to mini_chromium's LOG_VERBOSE, FATAL to LOG_FATAL, the rest 1:1.

Examples:

>type .sentry-native\4dda4ca5-4a48-4ce2-833f-41f130ea74d9.run\crashpad-client.log
[9888:16876:20260417,172244.413:ERROR crashpad_client_win.cc:615] CreateProcess: %1 is not a valid Win32 application. (193)
[9888:16876:20260417,172253.264:ERROR crashpad_client_win.cc:153] crash server failed to launch, self-terminating

>type .sentry-native\503a7424-7c3f-4644-755a-4b2d0469dbc4.run\crashpad-handler.log
[18468:19016:20260417,172034.322:ERROR filesystem_win.cc:115] GetFileAttributes C:\Users\jpnurmi\Projects\sentry\sentry-playground\build\Desktop_Qt_6_9_1_MSVC2022_64bit-RelWithDebInfo\.sentry-native\attachments\3d5e3570-9cbd-4f6f-40f5-1bdd786d7254\__sentry-event: The system cannot find the file specified. (2)
[18468:19016:20260417,172034.323:ERROR filesystem_win.cc:115] GetFileAttributes C:\Users\jpnurmi\Projects\sentry\sentry-playground\build\Desktop_Qt_6_9_1_MSVC2022_64bit-RelWithDebInfo\.sentry-native\attachments\3d5e3570-9cbd-4f6f-40f5-1bdd786d7254\__sentry-breadcrumb1: The system cannot find the file specified. (2)
[18468:19016:20260417,172034.324:ERROR filesystem_win.cc:115] GetFileAttributes C:\Users\jpnurmi\Projects\sentry\sentry-playground\build\Desktop_Qt_6_9_1_MSVC2022_64bit-RelWithDebInfo\.sentry-native\attachments\3d5e3570-9cbd-4f6f-40f5-1bdd786d7254\__sentry-breadcrumb2: The system cannot find the file specified. (2)
[18468:19016:20260417,172034.377:ERROR filesystem_win.cc:115] GetFileAttributes C:\Users\jpnurmi\Projects\sentry\sentry-playground\build\Desktop_Qt_6_9_1_MSVC2022_64bit-RelWithDebInfo\.sentry-native\attachments\3d5e3570-9cbd-4f6f-40f5-1bdd786d7254\screenshot.png: The system cannot find the file specified. (2)

Close: #1468

See also:

• feat: add --log-file and --log-level options crashpad#148
• feat: file logging and configurable minimum log level mini_chromium#6

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[jpnurmi]

@JoshuaMoelans What do you think about <run>/crashpad-handler.log for the handler side, and then either STDERR and/or <run>/crashpad-client.log for the client side. We can pass LOG_TO_STDERR to the client, but then crashpad-client.log becomes kind of redundant.

P.S. Neither of them barely logs almost anything at all. They seem to be mostly errors only.

[JoshuaMoelans]

@jpnurmi yeah that sounds good, it's where I would expect these logs to show up (crashpad being a different process, I also don't mind it not going to STDERR by default either)

[jpnurmi]

@JoshuaMoelans What about the client side that lives in the same process? It can also print useful errors, such as crashpad_handler missing +x on Linux. Here's a fabricated error with crashpad_handler.exe replaced by an empty file:

We can either capture client-side errors into STDERR so that it gets mixed in the sentry output (notice one message from crashpad_client_win.cc in the middle):

[sentry] INFO using database path "C:\Users\jpnurmi\Projects\sentry\sentry-playground\build\.sentry-native"
[sentry] DEBUG starting transport
[sentry] DEBUG starting background worker thread
[sentry] DEBUG submitting 100 ms delayed task to background worker thread
[sentry] DEBUG starting backend
[sentry] DEBUG background worker thread started
[sentry] DEBUG starting crashpad backend with handler "C:\Users\jpnurmi\Projects\sentry\sentry-playground\build\crashpad_handler.exe"
[sentry] DEBUG using minidump URL "https://127.0.0.1:12345/api/1/minidump/?sentry_client=sentry.native/0.13.7&sentry_key=aaa"
[19168:9228:20260420,170017.136:ERROR crashpad_client_win.cc:615] CreateProcess: %1 is not a valid Win32 application. (193)
[sentry] DEBUG registering crashpad WER handler "C:\Users\jpnurmi\Projects\sentry\sentry-playground\build\crashpad_wer.dll"
[sentry] WARN failed to start crashpad client handler
[sentry] WARN failed to initialize backend
[sentry] WARN `sentry_init` failed

Alternatively, we can capture it to <run>/crashpad-client.log:

C:\Users\jpnurmi\Projects\sentry\sentry-playground>type build\.sentry-native\c6a43bc8-2629-492d-e79c-94cb114aff09.run\crashpad-client.log
[19168:9228:20260420,170017.136:ERROR crashpad_client_win.cc:615] CreateProcess: %1 is not a valid Win32 application. (193)

Or, we can combine both so that you get crashpad-client.log and crashpad-handler.log side by side, even if the client-side logs appear in STDERR.