https://github.com/flightaware/tclreadline/pull/46

From 8c75e01b814ac852167611f5edae9659a1f709d2 Mon Sep 17 00:00:00 2001
From: Sam James <sam@gentoo.org>
Date: Wed, 23 Nov 2022 00:19:55 +0000
Subject: [PATCH 1/2] Fix configure.ac compatibility with Clang 16

Clang 16 makes -Wimplicit-function-declaration and -Wimplicit-int errors by default.

Unfortunately, this can lead to misconfiguration or miscompilation of software as configure
tests may then return the wrong result.

We also fix -Wstrict-prototypes while here as it's easy to do and it prepares
us for C23.

For more information, see LWN.net [0] or LLVM's Discourse [1], the Gentoo wiki [2],
or the (new) c-std-porting mailing list [3].

[0] https://lwn.net/Articles/913505/
[1] https://discourse.llvm.org/t/configure-script-breakage-with-the-new-werror-implicit-function-declaration/65213
[2] https://wiki.gentoo.org/wiki/Modern_C_porting
[3] hosted at lists.linux.dev.

Signed-off-by: Sam James <sam@gentoo.org>
--- a/configure.ac
+++ b/configure.ac
@@ -245,7 +245,8 @@ AC_TRY_LINK(,[
 AC_MSG_CHECKING([for the readline version number])
 AC_TRY_RUN([
 #include <stdio.h>
-int main () {
+#include <unistd.h>
+int main (void) {
     FILE *fp = fopen("conftestversion", "w");
     extern char *rl_library_version;
     fprintf(fp, "%s", rl_library_version);

From b64772750c7543fe66165fd7862b355d289412b6 Mon Sep 17 00:00:00 2001
From: Sam James <sam@gentoo.org>
Date: Wed, 23 Nov 2022 00:21:34 +0000
Subject: [PATCH 2/2] Fix -Wint-conversion in readline configure test

Fixes the following warning with Clang 16:
```
configure:12873: clang-16 -o conftest -g -O2   conftest.c -lreadline  >&5
conftest.c:33:11: error: incompatible pointer to integer conversion passing 'FILE *' (aka 'struct _IO_FILE *') to parameter of type 'int' [-Wint-conversion]
    close(fp);
          ^~
/usr/include/unistd.h:358:23: note: passing argument to parameter '__fd' here
extern int close (int __fd);
```

fopen should be paired with fclose.

Signed-off-by: Sam James <sam@gentoo.org>
--- a/configure.ac
+++ b/configure.ac
@@ -250,7 +250,7 @@ int main (void) {
     FILE *fp = fopen("conftestversion", "w");
     extern char *rl_library_version;
     fprintf(fp, "%s", rl_library_version);
-    close(fp);
+    fclose(fp);
     return 0;
 }],
     READLINE_VERSION=`cat conftestversion`