options/internal: detect underlying type of sigset_t

managarm · Oct 13, 2024 · 80bcdab · 80bcdab
1 parent 2c41220
commit 80bcdab
Showing 1 changed file with 46 additions and 9 deletions.
diff --git a/options/internal/generic/sigset.cpp b/options/internal/generic/sigset.cpp
@@ -3,6 +3,43 @@
 #include <errno.h>
 #include <limits.h>
 #include <string.h>
+#include <stddef.h>
+
+namespace {
+
+template<class T> struct remove_reference { typedef T type; };
+template<class T> struct remove_reference<T&> { typedef T type; };
+
+// Assume that the struct has a member named 'sig'.
+template<typename T>
+struct sigset_type_helper {
+	using type = typename remove_reference<decltype(T::sig[0])>::type;
+	static_assert(offsetof(T, sig) == 0);
+};
+
+template<>
+struct sigset_type_helper<unsigned long> {
+	using type = unsigned long;
+};
+
+template<>
+struct sigset_type_helper<long> {
+	using type = long;
+};
+
+// Some ABIs define sigset_t as a simple integer (e.g unsigned long),
+// while others define it as a struct containing an array of integers.
+using sigset_underlying_type = sigset_type_helper<sigset_t>::type;
+
+size_t signo_to_field(int signo) {
+	return signo / (sizeof(sigset_underlying_type) * CHAR_BIT);
+}
+
+size_t signo_to_bit(int signo) {
+	return signo % (sizeof(sigset_underlying_type) * CHAR_BIT);
+}
+
+} // namespace
 
 int sigemptyset(sigset_t *sigset) {
 	memset(sigset, 0, sizeof(*sigset));
@@ -20,9 +57,9 @@ int sigaddset(sigset_t *sigset, int sig) {
 		errno = EINVAL;
 		return -1;
 	}
-	auto ptr = reinterpret_cast<unsigned long *>(sigset);
-	int field = signo / (sizeof(unsigned long) * CHAR_BIT);
-	int bit = signo % (sizeof(unsigned long) * CHAR_BIT);
+	auto ptr = reinterpret_cast<sigset_underlying_type *>(sigset);
+	auto field = signo_to_field(signo);
+	auto bit = signo_to_bit(signo);
 	ptr[field] |= (1UL << bit);
 	return 0;
 }
@@ -33,9 +70,9 @@ int sigdelset(sigset_t *sigset, int sig) {
 		errno = EINVAL;
 		return -1;
 	}
-	auto ptr = reinterpret_cast<unsigned long *>(sigset);
-	int field = signo / (sizeof(unsigned long) * CHAR_BIT);
-	int bit = signo % (sizeof(unsigned long) * CHAR_BIT);
+	auto ptr = reinterpret_cast<sigset_underlying_type *>(sigset);
+	auto field = signo_to_field(signo);
+	auto bit = signo_to_bit(signo);
 	ptr[field] &= ~(1UL << bit);
 	return 0;
 }
@@ -46,8 +83,8 @@ int sigismember(const sigset_t *sigset, int sig) {
 		errno = EINVAL;
 		return -1;
 	}
-	auto ptr = reinterpret_cast<const unsigned long *>(sigset);
-	int field = signo / (sizeof(unsigned long) * CHAR_BIT);
-	int bit = signo % (sizeof(unsigned long) * CHAR_BIT);
+	auto ptr = reinterpret_cast<const sigset_underlying_type *>(sigset);
+	auto field = signo_to_field(signo);
+	auto bit = signo_to_bit(signo);
 	return (ptr[field] & (1UL << bit)) != 0;
 }