Add compile and link-time deprecation warnings for fgetln()

Although the current implementation in libbsd is probably one of the
safest ones around, it still poses some problems when used with many
file streams. This function has now a replacement, that is both more
standard and portable. Ask users to switch to getline(3) instead.

include/bsd/stdio.h

@@ -44,7 +44,12 @@
 __BEGIN_DECLS
 const char *fmtcheck(const char *, const char *);
 
-char *fgetln(FILE *fp, size_t *lenp);
+/* XXX: The function requires cooperation from the system libc to store the
+ * line buffer in the FILE struct itself. */
+char *fgetln(FILE *fp, size_t *lenp)
+	__attribute__((deprecated("This functions cannot be safely ported, "
+	                          "use getline(3) instead, as it is supported "
+	                          "by GNU and POSIX.1-2008.")));
 
 /*
  * Note: We diverge from the FreeBSD, OpenBSD and DragonFlyBSD declarations,

src/fgetln.c

@@ -30,6 +30,8 @@
 #include <sys/types.h>
 #include <string.h>
 
+#include "local-link.h"
+
 #ifdef HAVE_GETLINE
 struct filebuf {
 	FILE *fp;
@@ -68,6 +70,9 @@ fgetln(FILE *stream, size_t *len)
 		return fb->buf;
 	}
 }
+libbsd_link_warning(fgetln,
+                    "This functions cannot be safely ported, use getline(3) "
+                    "instead, as it is supported by GNU and POSIX.1-2008.")
 #else
 #error "Function fgetln() needs to be ported."
 #endif

test/Makefile.am

@@ -27,6 +27,7 @@ check_PROGRAMS += proctitle
 endif
 
 fgetln_SOURCES = test-stream.c test-stream.h fgetln.c
+fgetln_CFLAGS = -Wno-deprecated-declarations
 fparseln_SOURCES = test-stream.c test-stream.h fparseln.c
 
 proctitle_init_SOURCES = proctitle.c