Re: [xml] The order of arguments when compiling

[spam spam spam spam free fr]

Thank you for the answer but I use GNU Automake to build my Makefile automatically.
So, I can't set the good argument order easily.

My Makefile.am :
bin_PROGRAMS = xmlparsefile
xmlparsefile_SOURCES = main.c
xmlparsefile_LDFLAGS = `xml2-config --libs`
xmlparsefile_CFLAGS = -Wall -Wextra `xml2-config --cflags`

I think it's strange that GNU Automake do this choice if this is not compatible with most Unix linkers...

I will ask the GNU Automake mailing list to know if there is a way to set a different argument order than the 
default.

Any other suggestion is welcome.

----- Mail original -----
De: "Csaba Raduly" <rcsaba gmail com>
Ã: "spam spam spam spam" <spam spam spam spam free fr>
Cc: xml gnome org
EnvoyÃ: Vendredi 17 FÃvrier 2012 09:55:52
Objet: Re: [xml] The order of arguments when compiling

Hi spam,

On Thu, Feb 16, 2012 at 4:01 PM,   wrote:
> Hello,
>
> On a first computer, when I compile a C program using the libxml2 library I do :
> $ gcc `xml2-config --cflags` `xml2-config --libs` main.c
> or
> $ gcc main.c `xml2-config --cflags` `xml2-config --libs`
> And it works (but the first method is better because it respects the order of arguments in the gcc manual).
>
> On a second computer, if I compile like this, there is an error :
> $ gcc `xml2-config --cflags` `xml2-config --libs` main.c
> /tmp/cc7uNwed.o: In function `parseDoc':
> main.c:(.text+0xd): undefined reference to `xmlParseFile'
> main.c:(.text+0x51): undefined reference to `xmlCleanupParser'
> main.c:(.text+0x63): undefined reference to `xmlFreeDoc'
> main.c:(.text+0x68): undefined reference to `xmlCleanupParser'
> collect2: ld returned 1 exit status
> But if I compile like this, there is no error :
> $ gcc main.c `xml2-config --cflags` `xml2-config --libs`
>
> I thought this was a gcc problem but someone on the gcc mailing-list tell me that probably I have compiled 
> libxml2 on the second computer "statically". And I should compile it "dynamically". It's true that on the 
> second computer, I have compiled myself the library (configure, make, make install). On the first computer, 
> this is my distro package.
>
> How should I compile libxml2 on the 2nd computer to have the same behavior on the two computers?

You shouldn't; just use the last compilation command (with
`xml2-config --libs` at the end).
Most Unix linkers are one-pass; because of this, an object which needs
a symbol must appear before the object (or library) which supplies
that symbol.

See for example http://webpages.charter.net/ppluzhnikov/linker.html

GNU make's built-in rule for linking boils down to:

%: %.c
#  commands to execute (built-in):
         $(CC) $(CFLAGS) $(CPPFLAGS) $(LDFLAGS) $(TARGET_ARCH)      $^
    $(LOADLIBES) $(LDLIBS) -o $@

%: %.o
        $(CC) $(LDFLAGS) $(TARGET_ARCH)      $^      $(LOADLIBES)
$(LDLIBS) -o $@

As you can see, the list of source or object files ($^) is always
_before_ the list of libraries (in $(LDLIBS) or $(LOADLIBES) ).

Hope this helps,
Csaba
--
GCS a+ e++ d- C++ ULS$ L+$ !E- W++ P+++$ w++$ tv+ b++ DI D++ 5++
The Tao of math: The numbers you can count are not the real numbers.
Life is complex, with real and imaginary parts.
"Ok, it boots. Which means it must be bug-free and perfect. " -- Linus Torvalds
"People disagree with me. I just ignore them." -- Linus Torvalds