Replace signal() with sigaction() and add signal flags support#48
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sgerbino merged 1 commit intocppalliance:developfrom Jan 21, 2026
Merged
Replace signal() with sigaction() and add signal flags support#48sgerbino merged 1 commit intocppalliance:developfrom
sgerbino merged 1 commit intocppalliance:developfrom
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📝 WalkthroughWalkthroughThis PR implements POSIX signal flags support for Changes
Sequence DiagramsequenceDiagram
participant Caller as Application Code
participant API as signal_set::add<br/>(int, flags_t)
participant Validate as flags_supported<br/>flags_compatible
participant State as signal_state<br/>registered_flags
participant Register as posix_signals<br/>::add_signal
participant SA as sigaction()<br/>kernel
Caller->>API: add(SIGTERM, restart)
API->>Validate: flags_supported(restart)
alt Flags invalid
Validate-->>API: false
API-->>Caller: error
end
API->>State: Check registered_flags[SIGTERM]
alt First registration
State-->>API: (empty/none)
else Re-registration
State->>Validate: flags_compatible(existing, restart)
alt Incompatible flags
Validate-->>API: false
API-->>Caller: error
end
end
API->>Register: add_signal(impl, SIGTERM, restart)
Register->>Validate: to_sigaction_flags(restart)
Validate-->>Register: SA_RESTART
Register->>SA: sigaction(SIGTERM, &sa{flags=SA_RESTART})
SA-->>Register: success
Register->>State: registered_flags[SIGTERM] = restart
Register-->>API: success
API-->>Caller: result<void>()
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Actionable comments posted: 4
🤖 Fix all issues with AI agents
In `@include/boost/corosio/signal_set.hpp`:
- Around line 92-94: Update the doc comment in signal_set.hpp (the note near the
signal_set/flags description) to reflect actual Windows behavior: do not say
flags are "silently ignored"—state that on Windows the backend returns
operation_not_supported (error) for any flag other than none/dont_care; mention
that flags are only meaningful on POSIX and that callers should expect an
operation_not_supported error on Windows when passing unsupported flags. Refer
to signal_set and its flags in the comment so readers can locate the behavior.
In `@src/corosio/src/detail/posix/signals.cpp`:
- Around line 135-138: The code currently ignores requests for
signal_set::no_child_wait when SA_NOCLDWAIT is not defined; modify the handling
in src/corosio/src/detail/posix/signals.cpp so the caller is not misled: either
(A) add a compile-time guard that fails fast when signal_set::no_child_wait is
used but SA_NOCLDWAIT is unavailable (e.g. detect flags &
signal_set::no_child_wait and return a sentinel/error), or (B) emit a clear
runtime warning/error and return a failure code when flags contains
signal_set::no_child_wait but SA_NOCLDWAIT is undefined; update the caller
contract (function that consumes flags/returns sa_flags) to propagate this error
so callers can detect unsupported no_child_wait.
- Around line 75-77: deliver_signal() runs in a signal handler but currently
acquires non-async-signal-safe locks (e.g., std::mutex), which is undefined
behavior; change the implementation so the handler does not use mutexes: make
deliver_signal() perform only async-signal-safe actions (set a sig_atomic_t flag
or write a byte to a self-pipe/eventfd) and move the heavy work and any locking
into the main/event loop where handle_pending_signals() (or similar consumer
code) reads the flag/pipe and then acquires mutexes; update sigaction() setup
comments and/or document the new restriction if you choose a minimal change.
In `@src/corosio/src/detail/win/signals.hpp`:
- Around line 42-45: Update the comment in signals.hpp so it accurately
describes runtime behavior: replace "Signal flags are accepted but silently
ignored" with a note that unsupported signal flags are rejected at runtime with
operation_not_supported (or equivalent error), and mention that callers should
expect EOPNOTSUPP/operation_not_supported rather than silent no-op; ensure the
revised comment references the Windows-specific behavior already noted (use of C
runtime signal() and re-registration requirement) so maintainers see the
complete platform limitations.
🧹 Nitpick comments (1)
src/corosio/src/detail/posix/signals.cpp (1)
403-407: Useerrnofor accurate error reporting fromsigaction().When
sigaction()fails, the code returns a genericinvalid_argumenterror. The actual failure reason is inerrnoand could be more informative (e.g.,EINVALfor invalid signal number,EFAULTfor bad pointer).Suggested improvement
if (::sigaction(signal_number, &sa, nullptr) < 0) { delete new_reg; - return make_error_code(system::errc::invalid_argument); + return make_error_code(static_cast<system::errc>(errno)); }
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Actionable comments posted: 4
🤖 Fix all issues with AI agents
In `@doc/asio-feature-parity.md`:
- Around line 152-160: Update the Signal Handling table to reflect the new
corosio::signal_set implementation: change the Corosio column entries for
`signal_set`, `async_wait` for signals, and `Add/remove signals` from :x: to
:white_check_mark: (or a partial/conditional mark if you prefer), and update the
Notes cell to mention that corosio::signal_set is flag-aware and implemented via
sigaction() on POSIX, with Windows limitations (e.g., limited/partial support on
Windows). Specifically reference `corosio::signal_set` and mention the use of
`sigaction()` and the platform caveat in the Notes column.
In `@doc/epoll-for-dummies.md`:
- Around line 20-35: The fenced code/diagram blocks in the doc (for example the
ASCII diagram shown inside the triple backticks in the posix_scheduler diagram)
are missing language identifiers and trigger MD040; update each triple-backtick
fence to include an appropriate language tag (use text for ASCII diagrams and
cpp for C++ code examples) so markdownlint passes—apply this change to the
blocks around the shown snippet and the other ranges called out (71-110,
196-205, 240-262, 315-353, 481-507, 609-614, 625-637, 646-670, 762-798).
- Around line 371-378: The doc snippet shows corosio_posix_signal_handler
calling posix_signals::deliver_signal and then re-registering via
::signal(signal_number, corosio_posix_signal_handler); update it to reflect the
sigaction-based implementation by removing the re-registration line and noting
that sigaction persists the handler automatically (or briefly mention using
sigaction instead of signal), keeping corosio_posix_signal_handler and
posix_signals::deliver_signal references intact.
In `@doc/issues/sigaction-support.md`:
- Around line 148-149: Replace the two bare URLs by turning them into Markdown
inline links to satisfy MD034: change the lines containing "Boost.Asio
`signal_set`" and the Boost URL to a linked form like [Boost.Asio
`signal_set`](https://www.boost.org/doc/libs/release/doc/html/boost_asio/reference/signal_set.html)
and change the line containing "POSIX sigaction" and the POSIX URL to [POSIX
sigaction](https://pubs.opengroup.org/onlinepubs/9699919799/functions/sigaction.html);
ensure the visible text remains the descriptive labels (`signal_set` and
`sigaction`) so the markdownlint no-bare-urls rule is satisfied.
♻️ Duplicate comments (1)
src/corosio/src/detail/win/signals.hpp (1)
180-185: Alignadd_signalparam docs with the runtime flag validation.The param note says flags are ignored, but the header block says unsupported flags return
operation_not_supported. Aligning these avoids mixed guidance.📝 Suggested doc tweak
- `@param` flags The flags to apply (ignored on Windows). + `@param` flags Only `none` and `dont_care` are supported; other flags + return `operation_not_supported`.
🧹 Nitpick comments (2)
doc/issues/cpp-modules-support.md (1)
45-55: Add a language tag to the fenced block.MD040: the fence at Line 45 has no language; add one (e.g.,
text) to satisfy markdownlint.✅ Proposed fix
-``` +```text boost.corosio - Primary module interface boost.corosio:io_context - io_context and scheduler boost.corosio:socket - Socket types boost.corosio:acceptor - TCP acceptor boost.corosio:resolver - DNS resolver boost.corosio:read - Read operations boost.corosio:write - Write operations boost.corosio:tls - TLS stream (WolfSSL) boost.corosio:buffers - Buffer types (any_bufref, consuming_buffers)doc/issues/epollexclusive-thundering-herd.md (1)
50-50: Replace hardcoded line numbers with function/section references.The document references specific line numbers (
scheduler.cpp:94,sockets.hpp:462,doc/epoll-for-dummies.mdlines 621-643) which will become stale as the codebase evolves. Consider referencing by function name or section header instead.For example:
- Line 50: "registered in
scheduler::initialize_epoll()" instead of "scheduler.cpp:94"- Line 110: "in
socket::async_accept()" instead of "sockets.hpp:462"♻️ Proposed changes
-The eventfd used for wakeup signaling is registered at `scheduler.cpp:94`: +The eventfd used for wakeup signaling is registered in the scheduler initialization:-`EPOLLEXCLUSIVE` is also relevant for accept operations on listening sockets (`sockets.hpp:462`). When multiple threads wait to accept on the same socket, `EPOLLEXCLUSIVE` prevents all threads from waking on each incoming connection. +`EPOLLEXCLUSIVE` is also relevant for accept operations on listening sockets. When multiple threads wait to accept on the same socket, `EPOLLEXCLUSIVE` prevents all threads from waking on each incoming connection.-- Corosio documentation: `doc/epoll-for-dummies.md` (lines 621-643) +- Corosio documentation: `doc/epoll-for-dummies.md` (section on multi-threaded epoll usage)Also applies to: 110-110, 184-184
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Replace the POSIX signal() implementation with sigaction() and add support for signal flags (SA_RESTART, SA_NOCLDSTOP, etc.) while keeping OS-specific headers out of the public API. Public API changes: - Add flags_t enum directly to signal_set with abstract bit values - Add signal_set::add(int, flags_t) overload - Existing add(int) becomes inline convenience calling add(signal, none) - Add bitwise operators for flag manipulation (|, &, |=, &=, ~) Available flags: none, restart, no_child_stop, no_child_wait, no_defer, reset_handler, dont_care POSIX implementation (posix/signals.cpp): - Replace signal() with sigaction() for robust signal handling - Add flags_supported() to validate flags available on this platform - Add to_sigaction_flags() to map abstract flags to SA_* constants - Add flag conflict detection for multiple signal_sets on same signal - Remove handler re-registration (not needed with sigaction) - Track registered flags in global signal_state for cross-set validation - Return operation_not_supported if SA_NOCLDWAIT unavailable - Document async-signal-safety limitation in signal handler Windows implementation (win/signals.cpp): - Only none and dont_care flags are supported - Other flags return operation_not_supported Testing: Cross-platform tests for none/dont_care, POSIX-only tests for actual flag behavior, Windows-only test for operation_not_supported.
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Replace signal() with sigaction() and add signal flags support
Replace the POSIX signal() implementation with sigaction() and add
support for signal flags (SA_RESTART, SA_NOCLDSTOP, etc.) while
keeping OS-specific headers out of the public API.
Public API changes:
Available flags: none, restart, no_child_stop, no_child_wait, no_defer,
reset_handler, dont_care
POSIX implementation (posix/signals.cpp):
Windows implementation (win/signals.cpp):
Testing: Cross-platform tests for none/dont_care, POSIX-only tests for
actual flag behavior, Windows-only test for operation_not_supported.
Resolves #36.
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