POSIX requires <sys/select.h> for select function.

A patch being applied to TXR in the Void Linux distribution
informs me that the Musl library requires this. Traditional
Unix put the select materials in <sys/types.h> and <unistd.h>.

* configure: Add test for presence of <sys/select.h> and
whether that header actually declares select-related
declarations and macros. Define HAVE_SYS_SELECT_H
in config.h if so.

* socket.c: Conditionally include <sys/select.h>.

2 files changed, 27 insertions, 0 deletions

diff --git a/configure b/configure
index cb5aedb4..5b94d229 100755
--- a/configure
+++ b/configure
@@ -2801,6 +2801,30 @@ else
   printf "no\n"
 fi
 
+if [ $have_sockets ] ; then
+  printf "Checking whether we have <sys/select.h> ... "
+
+  cat > conftest.c <<!
+#include <sys/select.h>
+
+int main(int argc, char **argv)
+{
+  fd_set rfds;
+  int res;
+  FD_ZERO(&rfds);
+  FD_SET(0, &rfds);
+  res = res = select(1, &rfds, 0, 0, 0);
+  return 0;
+}
+!
+  if conftest; then
+    printf "yes\n"
+    printf "#define HAVE_SYS_SELECT_H 1\n" >> config.h
+  else
+    printf "no\n"
+  fi
+fi
+
 printf "Checking for getaddrinfo ... "
 
 cat > conftest.c <<!
diff --git a/socket.c b/socket.c
index 177c0e75..ace6944a 100644
--- a/socket.c
+++ b/socket.c
@@ -40,6 +40,9 @@
 #include <netdb.h>
 #include "config.h"
 #include ALLOCA_H
+#if HAVE_SYS_SELECT_H
+#include <sys/select.h>
+#endif
 #include "lib.h"
 #include "stream.h"
 #include "signal.h"