fix issues from public functions defined without declaration visible

policy is that all public functions which have a public declaration
should be defined in a context where that public declaration is
visible, to avoid preventable type mismatches.

an audit performed using GCC's -Wmissing-declarations turned up the
violations corrected here. in some cases the public header had not
been included; in others, a feature test macro needed to make the
declaration visible had been omitted.

in the case of gethostent and getnetent, the omission seems to have
been intentional, as a hack to admit a single stub definition for both
functions. this kind of hack is no longer acceptable; it's UB and
would not fly with LTO or advanced toolchains. the hack is undone to
make exposure of the declarations possible.

11 files changed, 22 insertions, 2 deletions

diff --git a/src/legacy/utmpx.c b/src/legacy/utmpx.c
index e2843c94..fa69f387 100644
--- a/src/legacy/utmpx.c
+++ b/src/legacy/utmpx.c
@@ -1,3 +1,4 @@
+#define _GNU_SOURCE
 #include <utmpx.h>
 #include <stddef.h>
 #include <errno.h>
diff --git a/src/linux/brk.c b/src/linux/brk.c
index ffdbbd52..a6173e07 100644
--- a/src/linux/brk.c
+++ b/src/linux/brk.c
@@ -1,3 +1,5 @@
+#define _BSD_SOURCE
+#include <unistd.h>
 #include <errno.h>
 #include "syscall.h"
 
diff --git a/src/linux/clone.c b/src/linux/clone.c
index b9e55945..8c1af7d3 100644
--- a/src/linux/clone.c
+++ b/src/linux/clone.c
@@ -1,5 +1,7 @@
+#define _GNU_SOURCE
 #include <stdarg.h>
 #include <unistd.h>
+#include <sched.h>
 #include "pthread_impl.h"
 #include "syscall.h"
 
diff --git a/src/linux/sbrk.c b/src/linux/sbrk.c
index 1e82d643..bb866305 100644
--- a/src/linux/sbrk.c
+++ b/src/linux/sbrk.c
@@ -1,3 +1,5 @@
+#define _BSD_SOURCE
+#include <unistd.h>
 #include <stdint.h>
 #include <errno.h>
 #include "syscall.h"
diff --git a/src/misc/getentropy.c b/src/misc/getentropy.c
index 4c61ae26..d2f282ce 100644
--- a/src/misc/getentropy.c
+++ b/src/misc/getentropy.c
@@ -1,3 +1,5 @@
+#define _BSD_SOURCE
+#include <unistd.h>
 #include <sys/random.h>
 #include <pthread.h>
 #include <errno.h>
diff --git a/src/misc/issetugid.c b/src/misc/issetugid.c
index 6ffd9300..ddc2ca0e 100644
--- a/src/misc/issetugid.c
+++ b/src/misc/issetugid.c
@@ -1,3 +1,4 @@
+#define _BSD_SOURCE
 #include <unistd.h>
 #include "libc.h"
 
diff --git a/src/misc/syscall.c b/src/misc/syscall.c
index 9d435a97..6f3ef656 100644
--- a/src/misc/syscall.c
+++ b/src/misc/syscall.c
@@ -1,3 +1,5 @@
+#define _BSD_SOURCE
+#include <unistd.h>
 #include "syscall.h"
 #include <stdarg.h>
 
diff --git a/src/network/ent.c b/src/network/ent.c
index ececdc48..5abea637 100644
--- a/src/network/ent.c
+++ b/src/network/ent.c
@@ -1,10 +1,16 @@
+#include <netdb.h>
 #include "libc.h"
 
 void sethostent(int x)
 {
 }
 
-void *gethostent()
+struct hostent *gethostent()
+{
+	return 0;
+}
+
+struct netent *getnetent()
 {
 	return 0;
 }
@@ -14,5 +20,4 @@ void endhostent(void)
 }
 
 weak_alias(sethostent, setnetent);
-weak_alias(gethostent, getnetent);
 weak_alias(endhostent, endnetent);
diff --git a/src/stdio/ext2.c b/src/stdio/ext2.c
index f359be9a..afd8b34e 100644
--- a/src/stdio/ext2.c
+++ b/src/stdio/ext2.c
@@ -1,4 +1,5 @@
 #include "stdio_impl.h"
+#include <stdio_ext.h>
 
 size_t __freadahead(FILE *f)
 {
diff --git a/src/stdio/fwide.c b/src/stdio/fwide.c
index 8410b153..8bab634a 100644
--- a/src/stdio/fwide.c
+++ b/src/stdio/fwide.c
@@ -1,3 +1,4 @@
+#include <wchar.h>
 #include "stdio_impl.h"
 #include "locale_impl.h"
 
diff --git a/src/thread/pthread_setattr_default_np.c b/src/thread/pthread_setattr_default_np.c
index ffd2712b..88503e34 100644
--- a/src/thread/pthread_setattr_default_np.c
+++ b/src/thread/pthread_setattr_default_np.c
@@ -1,3 +1,4 @@
+#define _GNU_SOURCE
 #include "pthread_impl.h"
 #include <string.h>