Use libxml2 in Linux 64 bits
lazarus / 66-Unix

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almp1 · 2016-07-25 02:12

Hello friends!

I use in my projects to libxml2-pascal library
https://sourceforge.net/projects/libxml2-pas/. Use a long time.
Already gone through various environments using this library. Used
environments are as follows:
1) Lazarus 1.4.x FPC 2.6.x on Windows 7.8 and 10 32 and 64 bits
2) Lazarus 1.6.x FPC 3.0.x on Windows 7.8 and 10 32 and 64 bits
3) Lazarus 1.4.x FPC 2.6.x Linux, Centos 6.7 distribution and Ubuntu
12.x and 14.x 32bits
4) Lazarus 1.6.x FPC 3.0.x Linux, Centos 6.7 distribution and Ubuntu
12.x and 14.x 32bits

The libxml2 library, both the DLL as the .so are version 2.9.4

But I can not use the library on Linux 64bits. I really need to use
this library in Linux 64bit environment, I've tried everything I know,
but it is always displayed the exception message

Linux 64 environment can make the library loading with
LoadLibrary ( 'libxml2.so');

But when I use GetProcess such as the following line:
 xmlStringComment: = PAnsiChar (GetProcAddress (libHandle
'xmlStringComment'));

I get the message below

System design raised exception class 'External: SIGSEGV'.
The address 7FFFF7DE4DF0

I do not know what to do, will that someone could help me with any
tips?

I thank you

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molly · 2016-07-25 05:23

Quote from: almp1 on July 25, 2016, 04:12:38 amLinux 64 environment
can make the library loading with
LoadLibrary ( 'libxml2.so');

But when I use GetProcess such as the following line:
 xmlStringComment: = PAnsiChar (GetProcAddress (libHandle
'xmlStringComment'));

I get the message below

System design raised exception class 'External: SIGSEGV'.
The address 7FFFF7DE4DF0
Since loadlibrary is a function returning a result, what does it
return for you ?

Note the part:
QuoteIf the library cannot be loaded, NilHandle is returned.

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mig-31 · 2016-07-25 08:04

If your application 64-bit check the path /usr/lib/ for library
exists, for 32-bit - /usr/lib32

If your see something like /usr/lib/libxml2.so.2.1 create a symbol
link libxml2.so -> libxml2.so.2.1

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almp1 · 2016-07-25 14:01

Hi Molly

The return has been a valid integer. In my code there is a line below

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i    
 libHandle: = LoadLibrary ('libxml2.so');   if libHandle <> 0 then 
 begin     __emptyExp: = xmlExpNodePtrPtr (GetProcAddress (libHandle
'emptyExp')); 
Still, thanks for the reply

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almp1 · 2016-07-25 14:04

Hi mig-31

Yes I checked the symbolic links, they are correct. If I cause an
error in the link symbolic return of LoadLibrary is NilHandle

Thanks for your response

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molly · 2016-07-25 16:41

Quote from: almp1 on July 25, 2016, 04:01:51 pmThe return has been a
valid integer. In my code there is a line below
Hmz strange.

Are you perhaps compiling a 64-bit program and loading a 32-bit
version of the library ?

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almp1 · 2016-07-25 17:00

Hi molly

Prepared every environment in 64bits, on a separate machine.
I made sure to ensure that no library 32bits stay active.
So was the test environment:

CentOS7 64bits
Lazarus 1.6 and FPC 3.0 64bits installed using RPM packages
Although the libraries are available in the yum repository CentOS7,
updated packages to their latest versions.
The xmlsec, xml2 and xslt libraries were downloaded here

ftp://xmlsoft.org/libxml2/

thanks for the reply

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Jonas Maebe · 2016-07-26 11:31

Is the type of the variable in which you store the result of
loadlibrary "TLibHandle"? It's an integer type, so if you assign it to
a 32 bit variable it will compile, but you will be truncating the
handle. Try compiling with range checking enabled to catch such
errors.

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almp1 · 2016-07-27 03:44

Hi  Jonas Maebe

I used your idea to change the type declaration of variable libhandle.
I was thus declaring libhandle: THandle. I made a change to libhandle:
TLibHandle. With this I managed to pass the __emptyExp: =
xmlExpNodePtrPtr (GetProcAddress (libHandle 'emptyExp'));

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i var 
//libHandle: THandle;  libHandle: TLibHandle;begin libHandle: =
LoadLibrary ('libxml2.so');   if libHandle <> 0 then   begin   
 __emptyExp: = xmlExpNodePtrPtr (GetProcAddress (libHandle
'emptyExp')); 
Now I have other pair identify challenges, but already helped me a lot

Thank you

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greaseflog · 2017-12-09 00:02

When the EError happen in Windows64 Ultimate that i have to do?


erro Illegal conversion type "LongInt" to "Integer"

code result.AddObject(wDescri, TObject (wCodigo))   ;

Lazarus 1.6
SVN r51630
FPC 3.0.0
x86_64-win64-win32/win64