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Re: Off-by-one error in windows-nat.c causes abort at startup


On 05/02/2016 05:39 PM, Eli Zaretskii wrote:
>> From: Pedro Alves <palves@redhat.com>

>>> --- gdb/windows-nat.c~	2016-02-10 05:19:39.000000000 +0200
>>> +++ gdb/windows-nat.c	2016-04-30 11:57:08.500000000 +0300
>>> @@ -2711,9 +2711,9 @@ _initialize_check_for_gdb_ini (void)
>>>        if (access (oldini, 0) == 0)
>>>  	{
>>>  	  int len = strlen (oldini);
>>> -	  char *newini = (char *) alloca (len + 1);
>>> +	  char *newini = (char *) alloca (len + 2);
>>>  
>>> -	  xsnprintf (newini, len + 1, "%.*s.gdbinit",
>>> +	  xsnprintf (newini, len + 2, "%.*s.gdbinit",
>>>  		     (int) (len - (sizeof ("gdb.ini") - 1)), oldini);
>>>  	  warning (_("obsolete '%s' found. Rename to '%s'."), oldini, newini);
>>
>> (I suspect this whole function could be rewritten in a clearer form...)
> 
> Like not use xsnprintf at all, and instead use strcpy/strcat, perhaps?
> 

Yeah, something like this (untested).

>From 33738f6c5bf7f76d6cb6853aecf880c5570f7d74 Mon Sep 17 00:00:00 2001
From: Pedro Alves <palves@redhat.com>
Date: Mon, 2 May 2016 18:57:50 +0100
Subject: [PATCH] Rewrite/simplify old gdb.ini warning

---
 gdb/windows-nat.c | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c
index 2e8a777..161e887 100644
--- a/gdb/windows-nat.c
+++ b/gdb/windows-nat.c
@@ -2694,27 +2694,28 @@ void
 _initialize_check_for_gdb_ini (void)
 {
   char *homedir;
+
   if (inhibit_gdbinit)
     return;
 
   homedir = getenv ("HOME");
-  if (homedir)
+  if (homedir != NULL)
     {
-      char *p;
-      char *oldini = (char *) alloca (strlen (homedir) +
-				      sizeof ("gdb.ini") + 1);
-      strcpy (oldini, homedir);
-      p = strchr (oldini, '\0');
-      if (p > oldini && !IS_DIR_SEPARATOR (p[-1]))
-	*p++ = '/';
-      strcpy (p, "gdb.ini");
+      size_t homedir_len = strlen (homedir);
+      char *oldini;
+
+      while (homedir_len > 0 && IS_DIR_SEPARATOR (homedir[homedir_len - 1]))
+	homedir_len--;
+
+      oldini = (char *) alloca (homedir_len + sizeof ("/gdb.ini"));
+      memcpy (oldini, homedir, homedir_len);
+      strcpy (oldini + homedir_len, "/gdb.ini");
       if (access (oldini, 0) == 0)
 	{
-	  int len = strlen (oldini);
-	  char *newini = (char *) alloca (len + 2);
+	  char *newini = (char *) alloca (homedir_len + sizeof ("/.gdbinit"));
 
-	  xsnprintf (newini, len + 2, "%.*s.gdbinit",
-		     (int) (len - (sizeof ("gdb.ini") - 1)), oldini);
+	  memcpy (newini, homedir, homedir_len);
+	  strcpy (newini + homedir_len, "/.gdbinit");
 	  warning (_("obsolete '%s' found. Rename to '%s'."), oldini, newini);
 	}
     }
-- 
2.5.5



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