fix addrinfo struct def

Fixes #4816

core/sys/posix/netdb.odin

@@ -352,15 +352,28 @@ when ODIN_OS == .Darwin || ODIN_OS == .FreeBSD || ODIN_OS == .NetBSD || ODIN_OS
 	// The highest reserved port number.
 	IPPORT_RESERVED :: 1024
 
-	addrinfo :: struct {
-		ai_flags:     Addrinfo_Flags, /* [PSX] input flags */
-		ai_family:    AF,             /* [PSX] address family of socket */
-		ai_socktype:  Sock,           /* [PSX] socket type */
-		ai_protocol:  Protocol,       /* [PSX] protocol of socket */
-		ai_addrlen:   socklen_t,      /* [PSX] length of socket address */
-		ai_canonname: cstring,        /* [PSX] canonical name of service location */
-		ai_addr:      ^sockaddr,      /* [PSX] binary address */
-		ai_next:      ^addrinfo,      /* [PSX] pointer to next in list */
+	when ODIN_OS == .Linux || ODIN_OS == .OpenBSD {
+		addrinfo :: struct {
+			ai_flags:     Addrinfo_Flags, /* [PSX] input flags */
+			ai_family:    AF,             /* [PSX] address family of socket */
+			ai_socktype:  Sock,           /* [PSX] socket type */
+			ai_protocol:  Protocol,       /* [PSX] protocol of socket */
+			ai_addrlen:   socklen_t,      /* [PSX] length of socket address */
+			ai_addr:      ^sockaddr,      /* [PSX] binary address */
+			ai_canonname: cstring,        /* [PSX] canonical name of service location */
+			ai_next:      ^addrinfo,      /* [PSX] pointer to next in list */
+		}
+	} else {
+		addrinfo :: struct {
+			ai_flags:     Addrinfo_Flags, /* [PSX] input flags */
+			ai_family:    AF,             /* [PSX] address family of socket */
+			ai_socktype:  Sock,           /* [PSX] socket type */
+			ai_protocol:  Protocol,       /* [PSX] protocol of socket */
+			ai_addrlen:   socklen_t,      /* [PSX] length of socket address */
+			ai_canonname: cstring,        /* [PSX] canonical name of service location */
+			ai_addr:      ^sockaddr,      /* [PSX] binary address */
+			ai_next:      ^addrinfo,      /* [PSX] pointer to next in list */
+		}
 	}
 
 	when ODIN_OS == .Darwin {

tests/core/sys/posix/structs/structs.c

@@ -1,3 +1,4 @@
+#include <stddef.h>
 #include <dirent.h>
 #include <fcntl.h>
 #include <glob.h>
@@ -70,6 +71,7 @@ int main(int argc, char *argv[])
 	printf("protoent %zu %zu\n", sizeof(struct protoent), _Alignof(struct protoent));
 	printf("servent %zu %zu\n", sizeof(struct servent), _Alignof(struct servent));
 	printf("addrinfo %zu %zu\n", sizeof(struct addrinfo), _Alignof(struct addrinfo));
+	printf("ai_canonname %zu\n", offsetof(struct addrinfo, ai_canonname));
 
 	printf("pollfd %zu %zu\n", sizeof(struct pollfd), _Alignof(struct pollfd));
 

tests/core/sys/posix/structs/structs.odin

@@ -38,6 +38,7 @@ main :: proc() {
 	fmt.println("protoent", size_of(posix.protoent), align_of(posix.protoent))
 	fmt.println("servent", size_of(posix.servent), align_of(posix.servent))
 	fmt.println("addrinfo", size_of(posix.addrinfo), align_of(posix.addrinfo))
+	fmt.println("ai_canonname", offset_of(posix.addrinfo, ai_canonname))
 
 	fmt.println("pollfd", size_of(posix.pollfd), align_of(posix.pollfd))
 	fmt.println("passwd", size_of(posix.passwd), align_of(posix.passwd))