clang-tidy: Catch-22 with signals?

[DarkTyger]

Consider t.cpp:

#include <signal.h>

int main() {
  struct sigaction action = {};
    
  action.sa_handler = []( int signum ) {};
  action.sa_flags = 0;
  ::sigemptyset( &action.sa_mask );
  ::sigaction( SIGUSR1, &action, nullptr );
}

Run:

clang-tidy --config-file=.clang-tidy src/t.cpp

Output:

t.cpp:1:10: warning: inclusion of deprecated C++ header 'signal.h'; consider using 'csignal' instead [modernize-deprecated-headers]
    1 | #include <signal.h>
      |          ^~~~~~~~~~
      |          <csignal>

Change, then run again:

#include <csignal>

int main() {
  struct sigaction action = {};

  action.sa_handler = []( int signum ) {};
  action.sa_flags = 0;
  ::sigemptyset( &action.sa_mask );
  ::sigaction( SIGUSR1, &action, nullptr );
}

Output:

t.cpp:4:10: warning: no header providing "sigaction" is directly included [misc-include-cleaner]
    2 | 
    3 | int main() {
    4 |   struct sigaction action = {};
      |          ^
t.cpp:6:10: warning: no header providing "sa_handler" is directly included [misc-include-cleaner]
    6 |   action.sa_handler = []( int signum ) {};
      |          ^
t.cpp:8:5: warning: no header providing "sigemptyset" is directly included [misc-include-cleaner]
    8 |   ::sigemptyset( &action.sa_mask );
      |     ^
t.cpp:9:5: warning: no header providing "sigaction" is directly included [misc-include-cleaner]
    9 |   ::sigaction( SIGUSR1, &action, nullptr );
      |     ^
t.cpp:9:16: warning: no header providing "SIGUSR1" is directly included [misc-include-cleaner]
    9 |   ::sigaction( SIGUSR1, &action, nullptr );
      |                ^

As sigaction is in POSIX, not the C++ standard, is it useful to warn against including signal.h? Is there a viable alternative?

See also: https://thomastrapp.com/posts/signal-handlers-for-multithreaded-c++/

[llvmbot]

@llvm/issue-subscribers-clang-include-cleaner

Author: None (DarkTyger)

Consider `t.cpp`:

#include <signal.h>

int main() {
  struct sigaction action = {};
    
  action.sa_handler = [](int signum ) {};
  action.sa_flags = 0;
  ::sigemptyset( &action.sa_mask );
  ::sigaction( SIGUSR1, &action, nullptr );
}

Run:

clang-tidy --config-file=.clang-tidy src/t.cpp

Output:

t.cpp:1:10: warning: inclusion of deprecated C++ header 'signal.h'; consider using 'csignal' instead [modernize-deprecated-headers]
    1 | #include <signal.h>
      |          ^~~~~~~~~~
      |          <csignal>

Change, then run again:

#include <csignal>

int main() {
  struct sigaction action = {};

  action.sa_handler = [](int signum ) {};
  action.sa_flags = 0;
  ::sigemptyset( &action.sa_mask );
  ::sigaction( SIGUSR1, &action, nullptr );
}

Output:

t.cpp:4:10: warning: no header providing "sigaction" is directly included [misc-include-cleaner]
    2 | 
    3 | int main() {
    4 |   struct sigaction action = {};
      |          ^
t.cpp:6:10: warning: no header providing "sa_handler" is directly included [misc-include-cleaner]
    6 |   action.sa_handler = [](int signum ) {};
      |          ^
t.cpp:8:5: warning: no header providing "sigemptyset" is directly included [misc-include-cleaner]
    8 |   ::sigemptyset( &action.sa_mask );
      |     ^
t.cpp:9:5: warning: no header providing "sigaction" is directly included [misc-include-cleaner]
    9 |   ::sigaction( SIGUSR1, &action, nullptr );
      |     ^
t.cpp:9:16: warning: no header providing "SIGUSR1" is directly included [misc-include-cleaner]
    9 |   ::sigaction( SIGUSR1, &action, nullptr );
      |                ^

As sigaction is in POSIX, not the C++ standard, is it useful to warn against including signal.h? Is there a viable alternative?

See also: https://thomastrapp.com/posts/signal-handlers-for-multithreaded-c++/

[EugeneZelenko]

@DarkTyger: Which STL implementation do you use? See also #73347.

[DarkTyger]

$ g++ --version
g++ (Debian 12.2.0-14) 12.2.0
$ clang-tidy --version
Debian LLVM version 19.0.0
$ make
g++ -x c++-header -I./compiled_include -Iinclude -MD -ggdb3 -std=c++17 ...