Re: [PATCH] don't store temporary value returned from c_str()

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+From: Tomi Ollila <tomi.ollila@iki.fi>\r
+To: Jani Nikula <jani@nikula.org>, Vladimir.Marek@oracle.com,\r
+       notmuch@notmuchmail.org\r
+Subject: Re: [PATCH] don't store temporary value returned from c_str()\r
+In-Reply-To: <878v44qhop.fsf@nikula.org>\r
+References: <1366405933-17223-1-git-send-email-Vladimir.Marek@oracle.com>\r
+       <878v44qhop.fsf@nikula.org>\r
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+Date: Sat, 27 Apr 2013 16:22:01 +0300\r
+Message-ID: <m261z8hzwm.fsf@guru.guru-group.fi>\r
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+Cc: Vladimir Marek <vlmarek@volny.cz>\r
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+\r
+On Sat, Apr 27 2013, Jani Nikula <jani@nikula.org> wrote:\r
+\r
+> On Sat, 20 Apr 2013, Vladimir.Marek@oracle.com wrote:\r
+>> From: Vladimir Marek <vlmarek@volny.cz>\r
+>>\r
+>> This is causing problems when compiled by Oracle Studio. Memory pointed\r
+>> by (const char*)term was already changed once talloc_strdup was called.\r
+>>\r
+>> Signed-off-by: Vladimir Marek <vlmarek@volny.cz>\r
+>> ---\r
+>>  lib/message.cc |    9 ++++-----\r
+>>  1 files changed, 4 insertions(+), 5 deletions(-)\r
+>>\r
+>> diff --git a/lib/message.cc b/lib/message.cc\r
+>> index 8720c1b..8d329d1 100644\r
+>> --- a/lib/message.cc\r
+>> +++ b/lib/message.cc\r
+>> @@ -266,18 +266,17 @@ _notmuch_message_get_term (notmuch_message_t *message,\r
+>>                        const char *prefix)\r
+>>  {\r
+>>      int prefix_len = strlen (prefix);\r
+>> -    const char *term = NULL;\r
+>>      char *value;\r
+>>  \r
+>>      i.skip_to (prefix);\r
+>>  \r
+>> -    if (i != end)\r
+>> -   term = (*i).c_str ();\r
+>\r
+> It's okay to use the result of .c_str() as long as the string object\r
+> stays in scope, and none of the non-const member functions are\r
+> called. Here, I think the problem is that TermIterator's overloaded\r
+> operator*() returns a string object within the if block's scope, and it\r
+> goes immediately out of scope. You could check this by adding\r
+>\r
+>      string s = *i;\r
+>\r
+> in function scope, and replacing (*i) with s in the if block. This might\r
+> also be more obvious than the presented patch, but I think the patch is\r
+> fine too.\r
+\r
+Thanks, now I understand. I'd like to see updated patch using Jani's\r
+example but I also think that the current patch is fine too.\r
+\r
+>\r
+> BR,\r
+> Jani.\r
+\r
+Tomi\r
+\r
+>\r
+>\r
+>> +    if (i == end)\r
+>> +   return NULL;\r
+>>  \r
+>> -    if (!term || strncmp (term, prefix, prefix_len))\r
+>> +    if (strncmp ((*i).c_str(), prefix, prefix_len))\r
+>>     return NULL;\r
+>>  \r
+>> -    value = talloc_strdup (message, term + prefix_len);\r
+>> +    value = talloc_strdup (message, (*i).c_str() + prefix_len);\r
+>>  \r
+>>  #if DEBUG_DATABASE_SANITY\r
+>>      i++;\r
+>> -- \r
+>> 1.7.3.2\r
+>>\r
+>> _______________________________________________\r
+>> notmuch mailing list\r
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+>> http://notmuchmail.org/mailman/listinfo/notmuch\r
+> _______________________________________________\r
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