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It's impossible to specify more than one external library to link using 
build_ext --libraries. Bug 716634 says that the problem is fixed, but it isn't. 
Assuming that the desired format is --libraries="lib1 lib2 etc", then there's a 
simple one line fix which I've attached. 
The problem exists in python 2.3.5, 2.4.1, 2.4.2 and in cvs HEAD. 

Another bug day task

This one is really annoying. Could you please consider fixing this one for the next release? (=lightweight change)

Distutils is frozen and we fix only bugs. This case is a little bit at the edge. 
Can you show us an example of a call you are trying to make, and the gcc command line output that fails ? 
I want to see if we can find a workaround. If so, this will be changed only in Distutils2. If not I'll change this to a bug and we'll fix it in distutils too.

I applied the patch proposed by slanger. This one is working.
Now, I'm executing this instruction to build my extension:
"%pythonRoot%\python.exe" setup.py build_ext --include-dirs "C:\MyApp\include" --library-dir "C:\MyApp\lib" --libraries "myLib1 myLib2"
If I don't use the patch, then the error I get is 'unresolved external symbol _xxx referenced in function _abc'. Which is quite normal since I can only point to one library...

Since "--libraries" is plural, and since the help text says:
--libraries (-l) external C libraries to link with
it should IMO be considered a bug.
(Standard UNIX linkers have a different convention: you can specify -l several times in order to link against several libraries; however, distutils seems to ignore all but the last -l option)

I agree this is a bug: it’s a broken feature, not a new one, even if it can be argued that fixing a long-standing behavior enables new usages, and is thus comparable to a new feature.
I found no mention of --libraries in the docs, so I looked at the file history, and it’s clear that the intent of the code does not match its behavior. The fix is simple:
- if isinstance(self.libraries, str):
- self.libraries = [self.libraries]
+ self.ensure_string_list('libraries')
I guess Greg forgot to change that line of code when he invented the ensure_* methods. No test is broken by this change. Do we need a regression test for this? It’s not strictly required IMO.
FTR, in distutils2, I want to make the types and formats clear for everything. For example, build_ext.swig_opts is defined as "a list" in the current docs, this time with an example that shows it’s space-separated ("--swig-opts="-modern -I../include""). The code does not use ensure_string_list, and hence does not support comma-separated. IMO, any value described as list should accept space-separated and comma-separated. This is probably out of scope for distutils, but something I definitely want to improve in distutils2. Supporting multiple options (-lm -lfoo) is IMO feasible too.

I’ve reviewed other modules for the same error and found two candidates: config.libraries, the same thing as build_ext.libraries, and install.extra_path, for which I’m not sure.
(More distutils2 thoughts: A number of options are split on os.pathsep, a new ensure_dirs_list method looks in order. Regarding the type system, an angry comment in build_py confirmed the need :)

Ran into this bug today in 2.7 (building python-sybase with freetds). The fix in msg121260 took care of it (didn't try the patch). Thanks, Éric. 
Is this something that could get patched in the upcoming micro releases? It's not so important for me at this point, and I'm not sure how often it will come up, but it's also a very simple fix.

New changeset 53df93a9c002 by Éric Araujo in branch '3.2':
Fix parsing of build_ext --libraries option (#1326113)
http://hg.python.org/cpython/rev/53df93a9c002
New changeset f7163afecb97 by Éric Araujo in branch 'default':
Merge fixes for #1326113 and #12297 from 3.2
http://hg.python.org/cpython/rev/f7163afecb97 

New changeset 96f5718bf005 by Éric Araujo in branch '2.7':
Fix parsing of build_ext --libraries option (#1326113)
http://hg.python.org/cpython/rev/96f5718bf005 

New changeset 4ba43318e56b by Éric Araujo in branch 'default':
Fix parsing of packaging’s build_ext --libraries option (#1326113)
http://hg.python.org/cpython/rev/4ba43318e56b 

New changeset 60dd0041c9bc by Éric Araujo in branch 'default':
Fix parsing of build_ext --libraries option (#1326113)
http://hg.python.org/distutils2/rev/60dd0041c9bc
New changeset 158697fd8fa1 by Éric Araujo in branch 'python3':
Merge #1326113 fix from default
http://hg.python.org/distutils2/rev/158697fd8fa1 

Here you are! Thanks for the testing.

New changeset 77ac369fbbf1 by Éric Araujo in branch '3.2':
Fix test failure for shared builds caused by #1326113 fix
http://hg.python.org/cpython/rev/77ac369fbbf1 

New changeset 98fb1c0fc7a0 by Éric Araujo in branch 'default':
Fix for packaging test failure on shared builds (#1326113)
http://hg.python.org/cpython/rev/98fb1c0fc7a0 

New changeset db1c52aa4d2a by Éric Araujo in branch '2.7':
Fix test failure for shared builds caused by #1326113 fix
http://hg.python.org/cpython/rev/db1c52aa4d2a 

Another instance of this is #1703178.