bjoernager/rust
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Explain SIGSEGV backtrace handler

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...to both compiler contributors and other rustc invokers.
The previous error messaging was extremely unfriendly,
and potentially both confusing and alarming.

The entire modules is extracted into a new file to help
ease of reading, and plenty of comments get layered in.
The design of the messaging is focused on preventing
the overall purpose of the output from being too opaque
in common cases, so users understand why it is there.
There's not an immediate need for it being actionable,
but some suggestions are offered anyways.
This commit is contained in:
Jubilee Young 2023-07-11 00:51:39 -07:00
parent 7bd81ee190
commit 4fa00c2507
2 changed files with 85 additions and 66 deletions
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75
compiler/rustc_driver_impl/src/lib.rs
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@ -78,6 +78,15 @@ pub mod pretty;
#[macro_use]
mod print;
mod session_diagnostics;
#[cfg(all(unix, any(target_env = "gnu", target_os = "macos")))]
mod signal_handler;
#[cfg(not(all(unix, any(target_env = "gnu", target_os = "macos"))))]
mod signal_handler {
/// On platforms which don't support our signal handler's requirements,
/// simply use the default signal handler provided by std.
pub(super) fn install() {}
}
use crate::session_diagnostics::{
RLinkEmptyVersionNumber, RLinkEncodingVersionMismatch, RLinkRustcVersionMismatch,
@ -1427,72 +1436,6 @@ pub fn init_env_logger(handler: &EarlyErrorHandler, env: &str) {
}
}
#[cfg(all(unix, any(target_env = "gnu", target_os = "macos")))]
mod signal_handler {
extern "C" {
fn backtrace_symbols_fd(
buffer: *const *mut libc::c_void,
size: libc::c_int,
fd: libc::c_int,
);
}
extern "C" fn print_stack_trace(_: libc::c_int) {
const MAX_FRAMES: usize = 256;
static mut STACK_TRACE: [*mut libc::c_void; MAX_FRAMES] =
[std::ptr::null_mut(); MAX_FRAMES];
unsafe {
let depth = libc::backtrace(STACK_TRACE.as_mut_ptr(), MAX_FRAMES as i32);
if depth == 0 {
return;
}
backtrace_symbols_fd(STACK_TRACE.as_ptr(), depth, 2);
}
}
/// When an error signal (such as SIGABRT or SIGSEGV) is delivered to the
/// process, print a stack trace and then exit.
pub(super) fn install() {
use std::alloc::{alloc, Layout};
unsafe {
let alt_stack_size: usize = min_sigstack_size() + 64 * 1024;
let mut alt_stack: libc::stack_t = std::mem::zeroed();
alt_stack.ss_sp = alloc(Layout::from_size_align(alt_stack_size, 1).unwrap()).cast();
alt_stack.ss_size = alt_stack_size;
libc::sigaltstack(&alt_stack, std::ptr::null_mut());
let mut sa: libc::sigaction = std::mem::zeroed();
sa.sa_sigaction = print_stack_trace as libc::sighandler_t;
sa.sa_flags = libc::SA_NODEFER | libc::SA_RESETHAND | libc::SA_ONSTACK;
libc::sigemptyset(&mut sa.sa_mask);
libc::sigaction(libc::SIGSEGV, &sa, std::ptr::null_mut());
}
}
/// Modern kernels on modern hardware can have dynamic signal stack sizes.
#[cfg(any(target_os = "linux", target_os = "android"))]
fn min_sigstack_size() -> usize {
const AT_MINSIGSTKSZ: core::ffi::c_ulong = 51;
let dynamic_sigstksz = unsafe { libc::getauxval(AT_MINSIGSTKSZ) };
// If getauxval couldn't find the entry, it returns 0,
// so take the higher of the "constant" and auxval.
// This transparently supports older kernels which don't provide AT_MINSIGSTKSZ
libc::MINSIGSTKSZ.max(dynamic_sigstksz as _)
}
/// Not all OS support hardware where this is needed.
#[cfg(not(any(target_os = "linux", target_os = "android")))]
fn min_sigstack_size() -> usize {
libc::MINSIGSTKSZ
}
}
#[cfg(not(all(unix, any(target_env = "gnu", target_os = "macos"))))]
mod signal_handler {
pub(super) fn install() {}
}
pub fn main() -> ! {
let start_time = Instant::now();
let start_rss = get_resident_set_size();