Add error dialog for critical errors on Windows by topolarity · Pull Request #54836 · JuliaLang/julia

topolarity · 2024-06-17T17:11:24Z

This change adds a small dialog for fatal errors on Windows:

with a corresponding entry in the Application log (in Event Viewer)

This is intended primarily for users of PackageCompiler.jl, who might be using Julia in a GUI application.

If a Julia-compiled library fails in a GUI application, users currently have no good way to know why/how their application crashed if, e.g., an exception was accidentally left unhandled in their Julia code.

Depends on #54835

TODO: Should this be a jl_options flag to determine whether to show the GUI? Should we log to the event log unconditionally? Is there any way that we can automatically detect whether stderr is connected to a terminal and user-visible?

fingolfin · 2024-07-24T12:34:04Z

+                event_source, EVENTLOG_ERROR_TYPE, /* category */ 0, /* event_id */ (DWORD)0xE0000000L,
+               /* user_sid */ NULL, /* n_strings */ 1, /* data_size */ 0, strings, /* data */ NULL
+            );
+            MessageBoxW(NULL, /* message */ L"error: libjulia received a fatal signal.\n\n"


I know very little about Windows, so my apologies if these questions are dumb, but: 1. Is this call async, or does it block?
2. Is this really safe to call here? In particular,
3. I am slightly worried about situations I experienced in an entirely different context were broadly similar code could lead to hundreds of dialog boxes spamming a user (when code that launched a ton of subprocesses to process data had them all fail simultaneously -- e.g. because a network connection dropped).

Anyway, none of this is meant as argument against this PR (which to me, as a non-Windows user, seems quite useful). Feel free to ignore me :-)

On 1: it blocks the thread.

a151cf3 added a jl_options guard

It's disabled by default now, but will be enabled by PackageCompiler when exporting Julia-based libraries - hopefully that resolves some of the concern. These are "critical" errors, so in some sense they should never happen (although in practice aggressive Ctrl-C at the REPL makes them happen quite a bit, so it's good that we don't alert in that case)

davidanthoff · 2024-07-24T14:18:48Z

Probably also needs to detect scenarios where no windows desktop is present? SSH, PowerShell remoting, running as a service etc.

Somehow making the dialog box optional seems like a good idea to me.

vtjnash

SGTM, I think this should work okay

DilumAluthge · 2025-09-18T15:17:32Z

Was this closed intentionally?

topolarity · 2025-09-18T23:04:38Z

Was this closed intentionally?

It was, but #54835 has since been re-opened

I'll be re-visiting this soon since "Julia as a library" scenarios on Windows are becoming relevant soon

This adds/changes a number of `fprint_*` variants to internal debug functions: - rename + new `ios_t *` argument: - `jl_critical_error` -> `jl_fprint_critical_error` - `jl_print_native_codeloc` -> `jl_fprint_native_codeloc` - `jl_print_bt_entry_codeloc` -> `jl_fprint_bt_entry_codeloc` - `jl_gc_debug_print_status` -> `jl_gc_debug_fprint_status` - `jl_gc_debug_critical_error` -> `jl_gc_debug_fprint_critical_error` - new `fprint_*` variants: - `jl_safe_fprintf` - `jl_safe_static_show` - `jl_fprint_backtrace(t)` Note that care needs to be taken w.r.t. what `ios_t *` value is passed into these functions from within a signal handler on Unix. Memory allocation is not async-signal-safe, so the ios_t needs to wrap a raw `fd_t` handle. Immediate motivation is #54836

vtjnash · 2025-09-20T01:38:39Z

build failure looks related

C:/workdir/src/support/ios.c:995:5: error: implicit declaration of function 'uv_wtf8_to_utf16' [-Wimplicit-function-declaration]
2025-09-19 20:40:54 EDT
  995 |     uv_wtf8_to_utf16(str, wstr, wlen);

This can be very useful when your Julia-built library hits an unexpected exception and causes a GUI-based application to crash with no error message.

This is disabled by default, but it can be enabled by downstream applications (in particular, by JuliaC.jl / PackageCompiler) so Windows users with a Julia library in a pure GUI application will get a useful error message for a crash.

topolarity · 2025-09-20T02:11:58Z

build failure looks related

C:/workdir/src/support/ios.c:995:5: error: implicit declaration of function 'uv_wtf8_to_utf16' [-Wimplicit-function-declaration]
2025-09-19 20:40:54 EDT
  995 |     uv_wtf8_to_utf16(str, wstr, wlen);

Fixed.

Do we have not have -Werror=implicit-function-declaration configured?

vtjnash · 2025-09-20T02:15:26Z

IIRC, Werror is currently only enabled for linux builders in buildkite, since nobody has thought to enable it for others

giordano · 2025-09-24T12:44:39Z

IIRC, Werror is currently only enabled for linux builders in buildkite, since nobody has thought to enable it for others

It's actually only missing for Windows (should be enabled already for all Unices platforms) because nobody went through all the warnings issued when targeting that platform, which is what Cody has now been working on starting with #59634

This adds/changes a number of `fprint_*` variants to internal debug functions: - rename + new `ios_t *` argument: - `jl_critical_error` -> `jl_fprint_critical_error` - `jl_print_native_codeloc` -> `jl_fprint_native_codeloc` - `jl_print_bt_entry_codeloc` -> `jl_fprint_bt_entry_codeloc` - `jl_gc_debug_print_status` -> `jl_gc_debug_fprint_status` - `jl_gc_debug_critical_error` -> `jl_gc_debug_fprint_critical_error` - new `fprint_*` variants: - `jl_safe_fprintf` - `jl_safe_static_show` - `jl_fprint_backtrace(t)` Note that care needs to be taken w.r.t. what `ios_t *` value is passed into these functions from within a signal handler on Unix. Memory allocation is not async-signal-safe, so the ios_t needs to wrap a raw `fd_t` handle. Immediate motivation is JuliaLang#54836

This change adds a small dialog (disabled by default) for fatal errors on Windows with a corresponding entry in the `Application` log (in Event Viewer, enabled by default) This is intended primarily for users of PackageCompiler.jl, who might be using Julia in a GUI application. If a Julia-compiled library fails in a GUI application, users currently have no good way to know why/how their application crashed if, e.g., an exception was accidentally left unhandled in their Julia code. Depends on JuliaLang#54835

topolarity mentioned this pull request Jun 17, 2024

NFC: Add fprint variants of internal print functions #54835

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giordano added system:windows Affects only Windows error handling Handling of exceptions by Julia or the user labels Jun 17, 2024

topolarity force-pushed the ct/more-fprint branch from 9f57800 to 37ce01c Compare June 17, 2024 17:17

topolarity force-pushed the ct/windows-alert branch 3 times, most recently from 7768244 to ca4254f Compare June 17, 2024 21:00

fingolfin reviewed Jul 24, 2024

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vtjnash reviewed Nov 18, 2024

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Comment thread src/signals-win.c Outdated

vtjnash reviewed Nov 18, 2024

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Comment thread src/support/ios.c Outdated

vtjnash reviewed Nov 18, 2024

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Comment thread src/signals-win.c Outdated

vtjnash reviewed Nov 18, 2024

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vtjnash closed this Sep 17, 2025

DilumAluthge reopened this Sep 18, 2025

topolarity force-pushed the ct/more-fprint branch 2 times, most recently from 377554f to d4137f1 Compare September 18, 2025 20:16

topolarity deleted the branch JuliaLang:master September 19, 2025 13:06

topolarity closed this Sep 19, 2025

topolarity reopened this Sep 19, 2025

topolarity changed the base branch from ct/more-fprint to master September 19, 2025 13:09

topolarity force-pushed the ct/windows-alert branch 2 times, most recently from 802487c to a151cf3 Compare September 19, 2025 13:33

vtjnash approved these changes Sep 19, 2025

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Comment thread src/task.c

topolarity force-pushed the ct/windows-alert branch from a151cf3 to f558752 Compare September 19, 2025 23:40

topolarity added the merge me PR is reviewed. Merge when all tests are passing label Sep 19, 2025

DilumAluthge removed the merge me PR is reviewed. Merge when all tests are passing label Sep 20, 2025

topolarity added 3 commits September 19, 2025 22:07

windows: Print unhandled exceptions to Application log

002c21c

This can be very useful when your Julia-built library hits an unexpected exception and causes a GUI-based application to crash with no error message.

windows: Print to Application log on critical error

07c9fea

topolarity force-pushed the ct/windows-alert branch from f558752 to 280cb72 Compare September 20, 2025 02:11

topolarity mentioned this pull request Sep 22, 2025

Use -Werror (with exceptions) on Windows builds JuliaCI/julia-buildkite#484

Merged

topolarity merged commit b83b35c into JuliaLang:master Sep 22, 2025
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topolarity commented Jun 17, 2024 •

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