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Merged
youknowone merged 4 commits into from
Dec 12, 2025
Merged

Faulthandler #6406

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2f34ee1
faulthandler errno
youknowone Dec 11, 2025
56b7451
faulthandler signals
youknowone Dec 11, 2025
cf3ad0a
apply review
youknowone Dec 11, 2025
ac33c4a
fix wasm32 build
youknowone Dec 11, 2025
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@youknowone
youknowone committed Dec 11, 2025
commit cf3ad0adafa07421d3909913eaca750a52cf8f69
88 changes: 32 additions & 56 deletions crates/stdlib/src/faulthandler.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -31,74 +31,50 @@ mod decl {
previous: libc::sighandler_t,
}

#[cfg(unix)]
impl FaultHandler {
const fn new(signum: libc::c_int, name: &'static str) -> Self {
Self {
signum,
enabled: false,
name,
// SAFETY: sigaction is a C struct that can be zero-initialized
previous: unsafe { std::mem::zeroed() },
}
}
}

#[cfg(windows)]
impl FaultHandler {
const fn new(signum: libc::c_int, name: &'static str) -> Self {
Self {
signum,
enabled: false,
name,
previous: 0,
}
}
}

/// faulthandler_handlers[]
/// Number of fatal signals
#[cfg(unix)]
const FAULTHANDLER_NSIGNALS: usize = 5;
#[cfg(windows)]
const FAULTHANDLER_NSIGNALS: usize = 3;
const FAULTHANDLER_NSIGNALS: usize = 4;

// CPython uses static arrays for signal handlers which requires mutable static access.
// This is safe because:
// 1. Signal handlers run in a single-threaded context (from the OS perspective)
// 2. FAULTHANDLER_HANDLERS is only modified during enable/disable operations
// 3. This matches CPython's faulthandler.c implementation
#[cfg(unix)]
static mut FAULTHANDLER_HANDLERS: [FaultHandler; FAULTHANDLER_NSIGNALS] = unsafe {
[
FaultHandler {
signum: libc::SIGBUS,
enabled: false,
name: "Bus error",
previous: std::mem::zeroed(),
},
FaultHandler {
signum: libc::SIGILL,
enabled: false,
name: "Illegal instruction",
previous: std::mem::zeroed(),
},
FaultHandler {
signum: libc::SIGFPE,
enabled: false,
name: "Floating-point exception",
previous: std::mem::zeroed(),
},
FaultHandler {
signum: libc::SIGABRT,
enabled: false,
name: "Aborted",
previous: std::mem::zeroed(),
},
FaultHandler {
signum: libc::SIGSEGV,
enabled: false,
name: "Segmentation fault",
previous: std::mem::zeroed(),
},
]
};

#[cfg(windows)]
static mut FAULTHANDLER_HANDLERS: [FaultHandler; FAULTHANDLER_NSIGNALS] = [
FaultHandler {
signum: libc::SIGFPE,
enabled: false,
name: "Floating-point exception",
previous: 0,
},
FaultHandler {
signum: libc::SIGABRT,
enabled: false,
name: "Aborted",
previous: 0,
},
FaultHandler {
signum: libc::SIGSEGV,
enabled: false,
name: "Segmentation fault",
previous: 0,
},
#[cfg(unix)]
FaultHandler::new(libc::SIGBUS, "Bus error"),
FaultHandler::new(libc::SIGILL, "Illegal instruction"),
FaultHandler::new(libc::SIGFPE, "Floating-point exception"),
FaultHandler::new(libc::SIGABRT, "Aborted"),
FaultHandler::new(libc::SIGSEGV, "Segmentation fault"),
];
Comment on lines +59 to +78
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@fanninpm fanninpm Dec 11, 2025

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When I was workshopping this on my own, prior to #6400, I came up with something similar to this, finding out from the libc repository that SIGILL does exist on Windows. Would this work?

Suggested change
/// faulthandler_handlers[]
/// Number of fatal signals
#[cfg(unix)]
const FAULTHANDLER_NSIGNALS: usize = 5;
#[cfg(windows)]
const FAULTHANDLER_NSIGNALS: usize = 3;
// CPython uses static arrays for signal handlers which requires mutable static access.
// This is safe because:
// 1. Signal handlers run in a single-threaded context (from the OS perspective)
// 2. FAULTHANDLER_HANDLERS is only modified during enable/disable operations
// 3. This matches CPython's faulthandler.c implementation
#[allow(static_mut_refs)]
#[cfg(unix)]
static mut FAULTHANDLER_HANDLERS: [FaultHandler; FAULTHANDLER_NSIGNALS] = unsafe {
[
FaultHandler {
signum: libc::SIGBUS,
enabled: false,
name: "Bus error",
previous: std::mem::zeroed(),
},
FaultHandler {
signum: libc::SIGILL,
enabled: false,
name: "Illegal instruction",
previous: std::mem::zeroed(),
},
FaultHandler {
signum: libc::SIGFPE,
enabled: false,
name: "Floating-point exception",
previous: std::mem::zeroed(),
},
FaultHandler {
signum: libc::SIGABRT,
enabled: false,
name: "Aborted",
previous: std::mem::zeroed(),
},
FaultHandler {
signum: libc::SIGSEGV,
enabled: false,
name: "Segmentation fault",
previous: std::mem::zeroed(),
},
]
};
#[allow(static_mut_refs)]
#[cfg(windows)]
static mut FAULTHANDLER_HANDLERS: [FaultHandler; FAULTHANDLER_NSIGNALS] = [
FaultHandler {
signum: libc::SIGFPE,
enabled: false,
name: "Floating-point exception",
previous: 0,
},
FaultHandler {
signum: libc::SIGABRT,
enabled: false,
name: "Aborted",
previous: 0,
},
FaultHandler {
signum: libc::SIGSEGV,
enabled: false,
name: "Segmentation fault",
previous: 0,
},
];
// CPython uses static arrays for signal handlers which requires mutable static access.
// This is safe because:
// 1. Signal handlers run in a single-threaded context (from the OS perspective)
// 2. FAULTHANDLER_HANDLERS is only modified during enable/disable operations
// 3. This matches CPython's faulthandler.c implementation
#[allow(static_mut_refs)]
static mut FAULTHANDLER_HANDLERS: [FaultHandler; if cfg!(unix) {5} else {4}] = unsafe {
[
#[cfg(unix)]
FaultHandler {
signum: libc::SIGBUS,
enabled: false,
name: "Bus error",
previous: std::mem::zeroed(),
},
FaultHandler {
signum: libc::SIGILL,
enabled: false,
name: "Illegal instruction",
previous: std::mem::zeroed(),
},
FaultHandler {
signum: libc::SIGFPE,
enabled: false,
name: "Floating-point exception",
previous: std::mem::zeroed(),
},
FaultHandler {
signum: libc::SIGABRT,
enabled: false,
name: "Aborted",
previous: std::mem::zeroed(),
},
FaultHandler {
signum: libc::SIGSEGV,
enabled: false,
name: "Segmentation fault",
previous: std::mem::zeroed(),
},
]
};
/// faulthandler_handlers[]
/// Number of fatal signals
const FAULTHANDLER_NSIGNALS: usize = FAULTHANDLER_HANDLERS.len();

You might also want a FaultHandler::default() implementation to same some repetition in the future.

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@youknowone youknowone Dec 11, 2025

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Thanks! applied it


/// fatal_error state
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