yyinput() didn't correctly store yy_hold_char

src/flex.skl

@@ -1893,8 +1893,8 @@ m4_ifdef( [[M4_YY_USE_LINENO]],
 		}
 
 	c = *(unsigned char *) YY_G(yy_c_buf_p);	/* cast for 8-bit char's */
-	*YY_G(yy_c_buf_p) = '\0';	/* preserve yytext */
 	YY_G(yy_hold_char) = *++YY_G(yy_c_buf_p);
+	*YY_G(yy_c_buf_p) = '\0';	/* preserve yytext */
 
 %% [19.0] update BOL and yylineno
 

tests/.gitignore

@@ -99,6 +99,8 @@ top
 top.[ch]
 yyextra
 yyextra.c
+yyinput
+yyinput.c
 tableopts_*.c
 *.opt
 *.ser

tests/Makefile.am

@@ -93,7 +93,8 @@ simple_tests = \
 	string_nr \
 	string_r \
 	top \
-	yyextra
+	yyextra \
+	yyinput
 
 reject_tests = \
 	reject_nr.reject \
@@ -182,6 +183,7 @@ string_r_SOURCES = string_r.l
 top_SOURCES = top.l top_main.c
 nodist_top_SOURCES = top.h
 yyextra_SOURCES = yyextra.l
+yyinput_SOURCES = yyinput.l
 
 # Normally, automake would distribute files built by flex. Since the
 # point of the test suite is to test the files that flex builds, and
@@ -261,6 +263,7 @@ CLEANFILES = \
 	top.c \
 	top.h  \
 	yyextra.c \
+	yyinput.c \
 	$(tableopts_c) \
 	$(tableopts_tables)
 

tests/yyinput.l

@@ -0,0 +1,100 @@
+/*
+ * This file is part of flex.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * Neither the name of the University nor the names of its contributors
+ * may be used to endorse or promote products derived from this software
+ * without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE.
+ */
+
+%{
+/* The goal of this test is to verify that yyinput() sets correct byte to null
+ * and also when called again it resets the correct byte to it's original value.
+ */
+#include <stdio.h>
+#include <stdlib.h>
+
+#define TESTBUF_SIZE 6
+
+static char testBuffers[][TESTBUF_SIZE] = {
+    "flex\0\0",
+    "FLEX\0\0"
+};
+
+/* C lexer defines input() instead of yyinput() */
+#ifndef __cplusplus
+#   define yyinput input
+#endif
+
+%}
+
+%option 8bit prefix="test"
+%option nounput nomain noyywrap
+%option warn posix-compat
+
+
+%%
+
+"fle" {
+    yyinput();
+}
+
+"F" {
+    yyinput();
+    yyinput();
+    yyinput();
+}
+
+%%
+
+int testYYInput(char* testBuf)
+{
+    YY_BUFFER_STATE state;
+
+    const char* origTestStr = strdup(testBuf);
+    state = test_scan_buffer(testBuf, TESTBUF_SIZE);
+    testlex();
+    yy_delete_buffer(state);
+    if (strcmp(origTestStr, testBuf) != 0)
+    {
+        printf("FAILED: Expected %s but left with %s\n", origTestStr, testBuf);
+        return 1;
+    }
+
+    free((void*) origTestStr);
+    printf("OK\n");
+    return 0;
+}
+
+int main (void)
+{
+    int result = 0;
+    /* Run the tests */
+    printf("Testing yyinput()\n");
+    result += testYYInput(testBuffers[0]);
+    result += testYYInput(testBuffers[1]);
+
+    if (result > 0)
+    {
+        printf("TEST FAILED.\n");
+        exit(1);
+    }
+
+    printf("TEST RETURNING OK.\n");
+    return 0;
+}
+