Python 3.6 can find cairo libs but not Python 2.7

[Peter Otten]

D'Arcy Cain wrote:

> On 2018-07-13 08:05 AM, Peter Otten wrote:
>> D'Arcy Cain wrote:
>>> Nope.  Both are 64 bit.
>> 
>> Just to be 100% sure, what does
>> 
>> $ python2.7 -c 'import struct; print(struct.calcsize("l"))'
>> 
>> $ python3.6 -c 'import struct; print(struct.calcsize("l"))'
>> 
>> print?
> 
> $ python2.7 -c 'import struct; print(struct.calcsize("l"))'
> 8
> $ python3.6 -c 'import struct; print(struct.calcsize("l"))'
> 8
> 
>> If both print 8, what is sys.platform? (This is just that I can look at
>> the right branch of the ctypes.util source for differences)?
> 
> $ python2.7 -c 'import sys; print(sys.platform)'
> netbsd7
> $ python3.6 -c 'import sys; print(sys.platform)'
> netbsd7
> 
> Thanks for checking this.

As far as I can see -- without having access to a netbsd machine -- this 
leads to the standard 'posix' implementation of find_library() which in both 
Python 2 and 3 runs /sbin/ldconfig and then searches its output with a 
regex.

On my (linux) machine that regex is the same for both python 2.7 and 3.6:

$ python3.6 -c 'import sys; sys.platform="netbsd7"; from ctypes import util; 
print(util.find_library("cairo"))'
XXX b'\\s+(libcairo\\.[^\\s]+)\\s+\\(libc6,x86-64'
libcairo.so.2
$ python2.7 -c 'import sys; sys.platform="netbsd7"; from ctypes import util; 
print(util.find_library("cairo"))'
YYY '\\s+(libcairo\\.[^\\s]+)\\s+\\(libc6,x86-64'
libcairo.so.2

Given the implementation

       def find_library(name):
            return _findSoname_ldconfig(name) or 
_get_soname(_findLib_gcc(name))

you might try calling _findSoname_ldconfig() directly -- if it fails for 
both 2.7 and 3.6 the next step would be to have a look at the fallback.