Similar to the commits earlier today about multiple input files for

MCA param files, ensure that we reset the flex buffer properly when we
start parsing a 2nd (or 3rd or 4th or ...) file.

This commit was SVN r3176.

src/util/show_help.c

@@ -137,6 +137,10 @@ static int open_file(const char *base, const char *topic)
         return OMPI_ERR_NOT_FOUND;
     }
 
+    /* Set the buffer */
+
+    ompi_show_help_init_buffer(ompi_show_help_yyin);
+
     /* Happiness */
 
     return OMPI_SUCCESS;

src/util/show_help_lex.h

@@ -19,7 +19,8 @@
 
 #include <stdio.h>
 
-extern int ompi_show_help_yylex(void);
+int ompi_show_help_yylex(void);
+int ompi_show_help_init_buffer(FILE *file);
 
 extern FILE *ompi_show_help_yyin;
 extern bool ompi_show_help_parse_done;

src/util/show_help_lex.l

@@ -65,8 +65,27 @@ int ompi_show_help_finish_parsing(void)
     return YY_NULL;
 }
 
+
 static int ompi_show_help_yywrap(void)
 {
     ompi_show_help_parse_done = true;
     return 1;
 }
+
+
+/*
+ * Ensure that we have a valid yybuffer to use.  Specifically, if this
+ * scanner is invoked a second time, finish_parsing() (above) will
+ * have been executed, and the current buffer will have been freed.
+ * Flex doesn't recognize this fact because as far as it's concerned,
+ * its internal state was already initialized, so it thinks it should
+ * have a valid buffer.  Hence, here we ensure to give it a valid
+ * buffer.
+ */
+int ompi_show_help_init_buffer(FILE *file)
+{
+    YY_BUFFER_STATE buf = yy_create_buffer(file, YY_BUF_SIZE);
+    yy_switch_to_buffer(buf);
+
+    return 0;
+}