can not link against libxml2

[Philipp Rosenberger]

When I try tolink against libxml2 I get undefined symbol errors from libxml2. Installed packages are: libxml2 libxml2-dev

I try to build the tutorial file from libxml2: http://www.xmlsoft.org/tutorial/apc.html

I try to build the programm like this:

gcc -o main $(xml2-config --cflags --libs) main.o

on other platforms (debian testing or ubuntu 10.04) this works flawlessly.

the complete output:
$ gcc -o main $(xml2-config --cflags --libs) main.o
main.o: In function `parseStory':
main.c:(.text+0x2f): undefined reference to `xmlStrcmp'
main.c:(.text+0x4f): undefined reference to `xmlNodeListGetString'
main.c:(.text+0x73): undefined reference to `xmlFree'
main.o: In function `parseDoc':
main.c:(.text+0xa9): undefined reference to `xmlParseFile'
main.c:(.text+0xe9): undefined reference to `xmlDocGetRootElement'
main.c:(.text+0x124): undefined reference to `xmlFreeDoc'
main.c:(.text+0x13e): undefined reference to `xmlStrcmp'
main.c:(.text+0x172): undefined reference to `xmlFreeDoc'
main.c:(.text+0x197): undefined reference to `xmlStrcmp'
main.c:(.text+0x1cd): undefined reference to `xmlFreeDoc'
collect2: ld returned 1 exit status

$ xml2-config --cflags
-I/usr/include/libxml2

xml2-config --libs
-L/usr/lib/x86_64-linux-gnu -lxml2

$ ls -l /usr/lib/x86_64-linux-gnu/libxml2.*
-rw-r--r-- 1 root root 2187982 May 18 21:52 /usr/lib/x86_64-linux-gnu/libxml2.a
-rw-r--r-- 1 root root 947 May 18 21:52 /usr/lib/x86_64-linux-gnu/libxml2.la
lrwxrwxrwx 1 root root 16 May 18 21:52 /usr/lib/x86_64-linux-gnu/libxml2.so -> libxml2.so.2.7.8
lrwxrwxrwx 1 root root 16 May 18 21:52 /usr/lib/x86_64-linux-gnu/libxml2.so.2 -> libxml2.so.2.7.8
-rw-r--r-- 1 root root 1417368 May 18 21:52 /usr/lib/x86_64-linux-gnu/libxml2.so.2.7.8

$ nm -D /usr/lib/x86_64-linux-gnu/libxml2.so |grep -e xmlStrcmp -e xmlNodeListGetString -e 'xmlFree$' -e xmlParseFile -e xmlDocGetRootElement -e 'xmlFreeDoc$'
0000000000054bd0 T xmlDocGetRootElement
0000000000358a08 D xmlFree
00000000000537e0 T xmlFreeDoc
0000000000051d50 T xmlNodeListGetString
000000000004e370 T xmlParseFile
00000000000aa9b0 T xmlStrcmp

[Philipp Rosenberger (philipp-rosenberger)]

Ubuntu version is 12.04 as amd64 and as x86.

[Jason Conti (jconti)]

Thanks for the bug report. With the changes to the linker in 11.10+, you must be sure when compiling to specify the -llibrary arguments after the objects that reference them.

In the case above:

gcc -o main $(xml2-config --cflags --libs) main.o

should be:

gcc -o main main.o $(xml2-config --cflags --libs)

so that the -llibrary args end up at the end of the command line. Please see http://wiki.debian.org/ToolChain/DSOLinking
for an overview of the changes.

[[e-mail] (marcond)]

I had the same problem when compiling libxenserver-6.0.0-1-src. The solution was the same as above, i.e. changing the line 65 of the Makefile like this:

 $(CC) $(LDFLAGS) -o $@ $< -L . -lxenserver

becomes:

 $(CC) -o $@ $< -L . -lxenserver $(LDFLAGS)

Then the compilation worked just fine.

Diff:
-----------------------
@@ -62,7 +62,7 @@
  $(AR) rcs libxenserver.a $^

 $(TEST_PROGRAMS): test/%: test/%.o libxenserver.so
- $(CC) $(LDFLAGS) -o $@ $< -L . -lxenserver
+ $(CC) -o $@ $< -L . -lxenserver $(LDFLAGS)

 .PHONY: install
-----------------------

[whitis (whitis)]

This unacceptable change in the linker has the potential to break many packages. Especially when:
cc=gcc $(include) $(libs)
prog1: prog1.c

[Dimitri John Ledkov (xnox)]

This is an intentional toolchain change, which brings significant benefits and features to Ubuntu. Similar changes are adopted by other distributions such as Debian and Fedora. Here are further details:

https://wiki.debian.org/ToolChain/DSOLinking

http://fedoraproject.org/wiki/UnderstandingDSOLinkChange