write once compile anywhere: mysqlclient

[hakelm]

Using libmysqlclient I have written a program for querying a MySQL database.
It compiles and runs without flaws under Linux i386 (Ubuntu) and Windows xp, 7, 8.1. Under Ubuntu AMD-64 queries, however, truncates fields and also returns empty fields.
Has anyone else seen this behaviour?
For the mysql-unit I use mysql.pp (Copyright (C) 2000 MySQL AB). I have both tried cdecl and stdcall for the function prototypes but this doesn't seem to matter.
My AMD-64 library is /usr/lib/x86_64-linux-gnu/libmysqlclient.so.18 from 21/1 2014.
Any tip is appreciated.
H

[Mike.Cornflake]

Both SQLDB and ZEOS provide working connections to MySQL.   I'm presuming you're writing your own for a reason, however you could look into their code, see how they do it...

[marcov]

mysql protocol etc are highly versioned. Make sure your mysql unit is prepared for 64-bit mysql and for the correct version.

Or use one of the supported versions that Mike named.

[LacaK]

For the mysql-unit I use mysql.pp (Copyright (C) 2000 MySQL AB). I have both tried cdecl and stdcall for the

From where do you use mysql.pp ? It is your own unit ?
(Can you try units (depends on version of your libmysqlclinet) from packages/mysql/src ?)

[hakelm]

No it's not my own unit, it can still be found on the internet and is similar to mysql4.pp coming with Lazarus.
I have used it without problems for around 10 years.
I believe that I now have found the problem. The new libmysqlclient for AMD-64 seems to have a bug in mysql_fetch_lengths which returns erroneous values.
The code below doesn't work:

Code: [Select]

.............
row:=prow(mysql_fetch_row(fmysqlresult));
while row<>nil do
begin
fieldlengths:=plengths(mysql_fetch_lengths(fmysqlresult));
for x:=0 to fieldcount-1 do
begin
l:=fieldlengths^[x];
pf:=row^ [x];
s:=copy(pf,1,l);
result[x,y]:=s;
end;
inc(y);
row:=prow(mysql_fetch_row(fmysqlresult));
end;

But this seems to correct the problem:

Code: [Select]

row:=prow(mysql_fetch_row(fmysqlresult));
while row<>nil do
begin
for x:=0 to fieldcount-1 do
begin
pf:=row^[x];
if pf<>nil then
result[x,y]:=pf
else
result[x,y]:='';
end;
inc(y);
row:=prow(mysql_fetch_row(fmysqlresult));
end;

H