Re: libpq bug?

Hi,

On Sat, Dec 29, 2018 at 1:37 AM patrick keshishian <pkeshish(at)gmail(dot)com> wrote:
&gt;
&gt; On Fri, Dec 28, 2018 at 5:40 PM Igor Korot <ikorot01(at)gmail(dot)com> wrote:
&gt;&gt;
&gt;&gt; Hi, Patrick,
&gt;&gt;
&gt;&gt; Here is my new code:
&gt;&gt;
&gt;&gt; int PostgresDatabase::GetTableOwner (const std::wstring
&amp;schemaName,
&gt;&gt; const std::wstring &amp;tableName, std::wstring &amp;owner,
&gt;&gt; std::vector<std::wstring> &amp;errorMsg)
&gt;&gt; {
&gt;&gt; int result = 0;
&gt;&gt; std::wstring query = L"SELECT u.usename FROM pg_class c, pg_user
&gt;&gt; u, pg_namespace n WHERE n.oid = c.relnamespace AND u.usesysid =
&gt;&gt; c.relowner AND n.nspname = $1 AND relname = $2";
&gt;&gt; char *values[2];
&gt;&gt; values[0] = NULL, values[1] = NULL;
&gt;&gt; int charlength1 = schemaName.length() * sizeof( wchar_t ),
&gt;&gt; charlength2 = tableName.length() * sizeof( wchar_t );
&gt;&gt; values[0] = new char[schemaName.length() * sizeof( wchar_t ) + 1];
&gt;&gt; values[1] = new char[tableName.length() * sizeof( wchar_t ) + 1];
&gt;&gt; memset( values[0], '\0', schemaName.length() * sizeof(
wchar_t ) + 1 );
&gt;&gt; memset( values[1], '\0', tableName.length() * sizeof(
wchar_t ) + 1 );
&gt;&gt; strcpy( values[0], m_pimpl-&gt;m_myconv.to_bytes(
schemaName.c_str()
&gt;&gt; ).c_str() );
&gt;&gt; strcpy( values[1], m_pimpl-&gt;m_myconv.to_bytes( tableName.c_str()
&gt;&gt; ).c_str() );
&gt;&gt; int len1 = (int) schemaName.length() * sizeof( wchar_t );
&gt;&gt; int len2 = (int) tableName.length() * sizeof( wchar_t );
&gt;&gt; int length[2] = { len1, len2 };
&gt;&gt; int formats[2] = { 1, 1 };
&gt;&gt; PGresult *res = PQexecParams( m_db, m_pimpl-&gt;m_myconv.to_bytes(
&gt;&gt; query.c_str() ).c_str(), 2, NULL, values, length, formats, 1 );
&gt;&gt; ExecStatusType status = PQresultStatus( res );
&gt;&gt; if( status != PGRES_COMMAND_OK &amp;&amp; status !=
PGRES_TUPLES_OK )
&gt;&gt; {
&gt;&gt; result = 1;
&gt;&gt; std::wstring err = m_pimpl-&gt;m_myconv.from_bytes(
&gt;&gt; PQerrorMessage( m_db ) );
&gt;&gt; errorMsg.push_back( L"Error executing query: " + err );
&gt;&gt; PQclear( res );
&gt;&gt; }
&gt;&gt; else
&gt;&gt; {
&gt;&gt; owner = m_pimpl-&gt;m_myconv.from_bytes( PQgetvalue(
res, 0, 0 ) );
&gt;&gt; }
&gt;&gt; return result;
&gt;&gt; }
&gt;&gt;
&gt;&gt; The charlength2 variable contains the value of 8 and I'm still getting
&gt;&gt; the same error.
&gt;
&gt;
&gt; I was hoping someone more versed in C++ would jump in to answer
your question. I haven't used C++ in at least a decade.
&gt; You need to convert the wchar_t data that wstring stores into
UTF-8. Personally, I would use iconv (common enough).

But that is very weird.
When I check what is stored in the values[1] array, I see the same
byte sequence as what I got from the database
information_schema.tables..
Maybe I should just upgrade the libpq and try the latest release?

&gt;
&gt; I assume the PostgresDatabase class is your own (?) I would add a
helper function to do the conversion. Here is a very rough template
for you to adapt if you think it helps you.

Yes, PostgresDatabase is my class.
I will look at that later today, but it would definitely be
interesting to get someone with the current C++
experience (especially with C++11), because I believe that I am doing
a conversion into UTF8.

The m_convert variable is declared as:

std::wstring_convert<std::codecvt_utf8<wchar_t> > m_myconv;

and so I think it is converting to the UTF8.

Thank you.

>
>
> #include <err.h>
>
> #include <stdlib.h>
>
> #include <string.h>
>
> #include <iostream>
>
> #include <string>
>
>
> #include <iconv.h>
>
>
> class PGDB {
>
> public:
>
> // your stuff ...
>
> iconv_t ic;
>
>
> PGDB(void) {
>
> setlocale(LC_CTYPE, "");
>
> ic = iconv_open("UTF-8", "wchar_t");
>
> if ((iconv_t)-1 == ic)
>
> errx(1, "iconv_open");
>
> }
>
> ~PGDB() {
>
> iconv_close(ic);
>
> }
>
> // caller should free()
>
> char *wchar2utf8(std::wstring const &ws) {
>
> char *in, *buf, *out;
>
> size_t bufsz, inbytes, outbytes;
>
>
> in = (char *)ws.data();
>
> inbytes = ws.length() * sizeof(wchar_t);
>
> outbytes = inbytes;
>
> bufsz = inbytes + 1; // XXX check for overflow
>
>
> buf = (char *)calloc(bufsz, 1);
>
> if (NULL == buf)
>
> err(1, NULL); // or throw something
>
>
> out = buf;
>
> if ((size_t)-1 == iconv(ic, &in, &inbytes, &out, &outbytes))
>
> errx(1, "iconv"); // or throw ...
>
>
> // TODO ensure inbytes is 0 (meaning all input consumed)
>
> return buf;
>
> }
>
> };
>
>
> // demo using above PGDB class/code
>
> int main(int argc, char *argv[])
>
> {
>
> char *str;
>
> size_t i, n;
>
> std::wstring tab;
>
> PGDB pg;
>
>
> tab = L"ºabcß";
>
> str = pg.wchar2utf8(tab);
>
>
> n = strlen(str);
>
> for (i = 0; i < n; ++i) {
>
> printf("%02hhx ", str[i]);
>
> }
>
> printf("\n");
>
> printf("->%s<-\n", str);
>
>
> free(str);
>
> return 0;
>
> }
>
>
>
> So in GetTableOwner() you'd call wchar2utf8() for the input wstring data and you don't do the new/memset/strcpy. Just remember to free() the returned utf8 string pointers after call to PQexecParams().
>
> cheers,
> --patrick
>
>
>
>>
>> Any idea?
>>
>> Thank you.
>>
>> On Fri, Dec 28, 2018 at 5:40 PM patrick keshishian <pkeshish(at)gmail(dot)com> wrote:
>> >
>> > On Fri, Dec 28, 2018 at 3:07 PM Igor Korot <ikorot01(at)gmail(dot)com> wrote:
>> >>
>> >> Hi,
>> >>
>> >> On Fri, Dec 28, 2018 at 4:51 PM patrick keshishian <pkeshish(at)gmail(dot)com> wrote:
>> >> >
>> >> >
>> >> > On Fri, Dec 28, 2018 at 2:00 PM Igor Korot <ikorot01(at)gmail(dot)com> wrote:
>> >> >>
>> >> >> Hi, ALL,
>> >> >> Following code:
>> >> >>
>> >> >> int PostgresDatabase::GetTableOwner (const std::wstring &schemaName,
>> >> >> const std::wstring &tableName, std::wstring &owner,
>> >> >> std::vector<std::wstring> &errorMsg)
>> >> >> {
>> >> >> int result = 0;
>> >> >> std::wstring query = L"SELECT u.usename FROM pg_class c, pg_user
>> >> >> u, pg_namespace n WHERE n.oid = c.relnamespace AND u.usesysid =
>> >> >> c.relowner AND n.nspname = $1 AND relname = $2";
>> >> >> char *values[2];
>> >> >> values[0] = NULL, values[1] = NULL;
>> >> >> values[0] = new char[schemaName.length() + 1];
>> >> >> values[1] = new char[tableName.length() + 1];
>> >> >> memset( values[0], '\0', schemaName.length() + 1 );
>> >> >> memset( values[1], '\0', tableName.length() + 1 );
>> >> >> strcpy( values[0], m_pimpl->m_myconv.to_bytes( schemaName.c_str()
>> >> >> ).c_str() );
>> >> >> strcpy( values[1], m_pimpl->m_myconv.to_bytes( tableName.c_str()
>> >> >> ).c_str() );
>> >> >> int len1 = (int) schemaName.length();
>> >> >> int len2 = (int) tableName.length();
>> >> >> int length[2] = { len1, len2 };
>> >> >> int formats[2] = { 1, 1 };
>> >> >> PGresult *res = PQexecParams( m_db, m_pimpl->m_myconv.to_bytes(
>> >> >> query.c_str() ).c_str(), 2, NULL, values, length, formats, 1 );
>> >> >> ExecStatusType status = PQresultStatus( res );
>> >> >> if( status != PGRES_COMMAND_OK && status != PGRES_TUPLES_OK )
>> >> >> {
>> >> >> result = 1;
>> >> >> std::wstring err = m_pimpl->m_myconv.from_bytes(
>> >> >> PQerrorMessage( m_db ) );
>> >> >> errorMsg.push_back( L"Error executing query: " + err );
>> >> >> PQclear( res );
>> >> >> }
>> >> >> else
>> >> >> {
>> >> >> owner = m_pimpl->m_myconv.from_bytes( PQgetvalue( res, 0, 0 ) );
>> >> >> }
>> >> >> return result;
>> >> >> }
>> >> >>
>> >> >> when ran with the call of
>> >> >>
>> >> >> GetTableOwner( "public", "abcß", owner, errorMsg );
>> >> >>
>> >> >> returns:
>> >> >>
>> >> >> ERROR: Invalid byte sequence for encoding UTF8.
>> >> >>
>> >> >> Does this mean I found the bug in the library?
>> >> >
>> >> >
>> >> > The bug is in your C++ code. "abcß" as tableName.lenght() (wstring) returns 4 (as in four characters) not number of bytes required to represent the intended string: 61 62 63 c3 9f
>> >> > Since the last character is a 2 bytes in length. Therefore, your call to PQexecParams() specifies a shorter length and hence an invalid UTF-8 sequence.
>> >> >
>> >> > Furthermore, your value[] array allocation is in error since wstring::length returns number of characters, not number of bytes. so you will end up with buffer-overflows.
>> >>
>> >> So I should use
>> >> https://stackoverflow.com/questions/9278723/how-can-i-get-the-byte-size-of-stdwstring
>> >> in both places?
>> >
>> >
>> > size() also returns 4. If you multiply it with sizeof(wchar_t) you will end up with maximum buffers size necessary to hold the string (minus terminating \0), but not the correct length you are after. I am unsure of the "correct" C++ solution.
>> >
>> > Sorry,
>> > --patrick
>> >
>> >
>> >>
>> >> Thank you.
>> >>
>> >> >
>> >> > HTH,
>> >> > --patrick
>> >> >
>> >> >
>> >> >>
>> >> >> Any idea what I can do?
>> >> >>
>> >> >> Thank you.
>> >> >>