From b3e9e62599532050fc776c5e8f076915b56c2235 Mon Sep 17 00:00:00 2001
From: David Faulkner <d@davo.co>
Date: Fri, 7 Aug 2026 23:40:47 -0500
Subject: Import official C23 code examples for Modern C (Jens Gustedt, 2024)

- Add official C source files, Makefile, c23-fallback.h, and LICENSE
- Update README.md with study mirror notice
---
 sighandler.h | 101 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)
 create mode 100644 sighandler.h

(limited to 'sighandler.h')

diff --git a/sighandler.h b/sighandler.h
new file mode 100644
index 0000000..4b7768d
--- /dev/null
+++ b/sighandler.h
@@ -0,0 +1,101 @@
+#ifndef SIGHANDLER_H
+#define SIGHANDLER_H 1
+
+#include "c23-fallback.h"
+#include <stdio.h>
+#ifndef __STDC_NO_ATOMIC__
+# include <stdatomic.h>
+#endif
+
+/**
+ ** @brief A pair of strings to hold signal information
+ **/
+struct sh_pair {
+  char const* name;
+  char const* desc;
+};
+typedef struct sh_pair sh_pair;
+
+/**
+ ** @brief For each possible signal, this holds a pair of strings with
+ ** signal information.
+ **
+ ** The size of this array can be queried with `sh_known`.
+ **
+ ** @see SH_PRINT to use that information.
+ **
+ ** Conditionally, this also adds some commonly used extensions.
+ **/
+extern sh_pair const sh_pairs[];
+
+extern size_t const sh_known;
+
+#if ATOMIC_LONG_LOCK_FREE > 1
+/**
+ ** @brief Keep track of the number of calls into a
+ **  signal handler for each possible signal.
+ **
+ ** Don't use this array directly.
+ **
+ ** @see sh_count to update this information.
+ ** @see SH_PRINT to use that information.
+ **/
+extern _Atomic(unsigned long) sh_counts[];
+
+/**
+ ** @brief Use this in your signal handler to keep track of the
+ ** number of calls to the signal @a sig.
+ **
+ ** @see sh_counted to use that information.
+ **/
+inline
+void sh_count(int sig) {
+  if (sig < sh_known) ++sh_counts[sig];
+}
+
+inline
+unsigned long sh_counted(int sig){
+  return (sig < sh_known) ? sh_counts[sig] : 0;
+}
+
+#else
+inline
+void sh_count(int sig) {
+  // empty
+}
+
+inline
+unsigned long sh_counted(int sig){
+  return 0;
+}
+#endif
+
+/**
+ ** @brief Prototype of signal handlers
+ **/
+typedef void sh_handler(int);
+
+/**
+ ** @brief Pretty-prints signal information
+ **
+ ** @see PRINT_SIG for a convenient user interface
+ **/
+void sh_print(FILE* io, int sig,
+              char const* filename, size_t line,
+              char const* string);
+
+/**
+ ** @brief Pretty-prints signal information
+ **
+ ** This prints signal information @a STRING for signal @a SIG to
+ ** stream @a IO.
+ **/
+#define SH_PRINT(IO, SIG, STRING) sh_print(IO, SIG, __FILE__, __LINE__, STRING)
+
+/**
+ ** @brief Enables a signal handler and catches the errors
+ **/
+sh_handler* sh_enable(int sig, sh_handler* hnd);
+
+
+#endif
-- 
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