[perl #55154] [BUG] [PATCH] readline not detected in c++ build

[via RT]

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readline is not detected when building with C++, because the detection
and the usage code declares directly the functions used without C
linkage specification.

This patch fixes the problem, and also do a minor cleaning in the
set_readline_interactive method of parrotio.pmc.

-- 
Salu2

Index: src/pmc/parrotio.pmc
===================================================================
--- src/pmc/parrotio.pmc	(revisión: 28004)
+++ src/pmc/parrotio.pmc	(copia de trabajo)
@@ -24,9 +24,15 @@
 #include "../src/io/io_private.h"
 
 #ifdef PARROT_HAS_READLINE
-extern char *readline(const char*);
+#ifdef __cplusplus
+extern "C" {
+#endif
+char *readline(const char*);
 void add_history(const char*);
+#ifdef __cplusplus
+}
 #endif
+#endif
 
 pmclass ParrotIO need_ext {
 
@@ -171,25 +177,25 @@
 
     METHOD set_readline_interactive(INTVAL on) {
         ParrotIO * const io = (ParrotIO *)PMC_data(SELF);
-#ifdef PARROT_HAS_READLINE
-        INTVAL flag;
-#endif
         if (!io)
             RETURN(INTVAL -2);
-
         if (!(io->flags & PIO_F_READ))
             RETURN(INTVAL -2);
+
 #ifdef PARROT_HAS_READLINE
-        if (on && !(io->flags & PIO_F_CONSOLE))
-            RETURN(INTVAL -2);
-        flag = !!(io->flags & PIO_F_READLINE);
+        {
+            INTVAL flag;
+            if (on && !(io->flags & PIO_F_CONSOLE))
+                RETURN(INTVAL -2);
+            flag = !!(io->flags & PIO_F_READLINE);
 
-        if (on)
-            io->flags |= PIO_F_READLINE;
-        else
-            io->flags &= ~PIO_F_READLINE;
+            if (on)
+                io->flags |= PIO_F_READLINE;
+            else
+                io->flags &= ~PIO_F_READLINE;
 
-        RETURN(INTVAL flag);
+            RETURN(INTVAL flag);
+        }
 #else
         RETURN(INTVAL -1);
 #endif
Index: config/auto/readline/readline.in
===================================================================
--- config/auto/readline/readline.in	(revisión: 28004)
+++ config/auto/readline/readline.in	(copia de trabajo)
@@ -11,8 +11,14 @@
  * the typedefs or prototypes of readline.  Let's boldly make stuff up
  * and even lie for the sake of this test. */
 
-extern char* readline(const char*);
-extern void* rl_get_keymap(void); 
+#ifdef __cplusplus
+extern "C" {
+#endif
+char* readline(const char*);
+void* rl_get_keymap(void); 
+#ifdef __cplusplus
+}
+#endif
 
 int main(int argc, char *argv[])
 {